fbo: Add a test for alpha testing with multiple render targets

Submitted by Anuj Phogat on Oct. 25, 2016, 10:58 p.m.

Details

Message ID 1477436305-1735-1-git-send-email-anuj.phogat@gmail.com
State New
Headers show
Series "fbo: Add a test for alpha testing with multiple render targets" ( rev: 1 ) in Piglit

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Commit Message

Anuj Phogat Oct. 25, 2016, 10:58 p.m.
In a situation when there are multiple render targets with alpha testing
enabled, if fragment shader doesn't write to draw buffer zero, alpha
value used for alpha testing will be undefined. Such case should not
cause a GPU hang.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
---
 tests/all.py                                       |   1 +
 tests/fbo/CMakeLists.gl.txt                        |   1 +
 tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c | 145 +++++++++++++++++++++
 3 files changed, 147 insertions(+)
 create mode 100644 tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c

Patch hide | download patch | download mbox

diff --git a/tests/all.py b/tests/all.py
index 9b67bae..9e4420e 100644
--- a/tests/all.py
+++ b/tests/all.py
@@ -4196,6 +4196,7 @@  with profile.group_manager(
         grouptools.join('spec', 'arb_draw_buffers')) as g:
     g(['arb_draw_buffers-state_change'], run_concurrent=False)
     g(['fbo-mrt-alphatest'], run_concurrent=False)
+    g(['fbo-mrt-alphatest-no-buffer-zero-write'], run_concurrent=False)
     g(['fbo-mrt-new-bind'], run_concurrent=False)
 
 with profile.group_manager(
diff --git a/tests/fbo/CMakeLists.gl.txt b/tests/fbo/CMakeLists.gl.txt
index 2e2cac9..e2c03ca 100644
--- a/tests/fbo/CMakeLists.gl.txt
+++ b/tests/fbo/CMakeLists.gl.txt
@@ -73,6 +73,7 @@  piglit_add_executable (fbo-integer fbo-integer.c)
 piglit_add_executable (fbo-maxsize fbo-maxsize.c)
 piglit_add_executable (fbo-mipmap-copypix fbo-mipmap-copypix.c)
 piglit_add_executable (fbo-mrt-alphatest fbo-mrt-alphatest.c)
+piglit_add_executable (fbo-mrt-alphatest-no-buffer-zero-write fbo-mrt-alphatest-no-buffer-zero-write.c)
 piglit_add_executable (fbo-mrt-new-bind fbo-mrt-new-bind.c)
 piglit_add_executable (fbo-nodepth-test fbo-nodepth-test.c)
 piglit_add_executable (fbo-nostencil-test fbo-nostencil-test.c)
diff --git a/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
new file mode 100644
index 0000000..ef56d89
--- /dev/null
+++ b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
@@ -0,0 +1,145 @@ 
+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+/*
+ * This test asserts correct behavior for alpha-testing of fragments when
+ * multiple color buffers are being rendered to. In particular, the alpha
+ * component of the color output to draw buffer zero is used for the alpha
+ * test. If draw buffer zero is not written by the fragment shader, alpha
+ * value used for alpha testing is undefined. This test should run to
+ * completion without a GPU hang.
+ *
+ * This is important for deferred renderers which use alpha-test, and is a
+ * significant edge case for the i965 driver.
+ */
+
+#include "piglit-util-gl.h"
+
+PIGLIT_GL_TEST_CONFIG_BEGIN
+
+	config.supports_gl_compat_version = 21;
+
+	config.window_visual = PIGLIT_GL_VISUAL_RGBA | PIGLIT_GL_VISUAL_DOUBLE;
+
+PIGLIT_GL_TEST_CONFIG_END
+
+GLenum buffers[] = {GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2};
+GLuint fbo;
+GLint prog;
+GLuint color0, color1, color2;
+
+void
+piglit_init(int argc, char **argv)
+{
+	piglit_require_GLSL_version(130);
+
+	glGenFramebuffers(1, &fbo);
+	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+
+	glGenTextures(1, &color0);
+	glBindTexture(GL_TEXTURE_2D, color0);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, color0, 0);
+
+	glGenTextures(1, &color1);
+	glBindTexture(GL_TEXTURE_2D, color1);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, color1, 0);
+
+	glGenTextures(1, &color2);
+	glBindTexture(GL_TEXTURE_2D, color2);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_2D, color2, 0);
+
+	glDrawBuffers(3, buffers);
+
+	prog = piglit_build_simple_program(
+		"#version 130\n"
+		"in vec4 pos;\n"
+		"void main() {\n"
+		"	gl_Position = pos;\n"
+		"}\n",
+
+		"#version 130\n"
+		"void main() {\n"
+		"	float alpha = float(int(gl_FragCoord.x / 16 + gl_FragCoord.y / 16) % 2);\n"
+		"	/*Don't write color to draw buffer zero i.e. gl_FragData[0] */\n"
+		"	gl_FragData[1] = vec4(1.0, 0.0, 0.0, alpha);\n"
+		"	gl_FragData[2] = vec4(0.0, 1.0, 0.0, 1.0);\n"
+		"}\n"
+		);
+
+	if (!piglit_check_gl_error(GL_NO_ERROR)) {
+		printf("Setup for test failed.\n");
+		piglit_report_result(PIGLIT_SKIP);
+	}
+
+	if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
+		printf("Framebuffer not complete.\n");
+		piglit_report_result(PIGLIT_SKIP);
+	}
+}
+
+
+enum piglit_result
+piglit_display(void)
+{
+	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+	glClearColor(0,0,1,0);
+	glClear(GL_COLOR_BUFFER_BIT);
+
+	glAlphaFunc(GL_GEQUAL, 0.5f);
+	glEnable(GL_ALPHA_TEST);
+
+	glUseProgram(prog);
+	glViewport(0, 0, 64, 64);
+	piglit_draw_rect(-1, -1, 2, 2);
+
+	glDisable(GL_ALPHA_TEST);
+
+	/* Visualize it */
+	glUseProgram(0);
+	glBindFramebuffer(GL_FRAMEBUFFER, piglit_winsys_fbo);
+	glViewport(0, 0, 128, 64);
+	glClearColor(0,0,0.5,0);
+	glClear(GL_COLOR_BUFFER_BIT);
+
+	glEnable(GL_TEXTURE_2D);
+	glBindTexture(GL_TEXTURE_2D, color1);
+	piglit_draw_rect_tex(-1, -1, 1, 2,
+			0, 0, 1, 1);
+	glBindTexture(GL_TEXTURE_2D, color2);
+	piglit_draw_rect_tex(0, -1, 1, 2,
+			0, 0, 1, 1);
+	glDisable(GL_TEXTURE_2D);
+	piglit_present_results();
+
+	/* If test executes to completion, return PIGLIT_PASS */
+	return PIGLIT_PASS;
+}

Comments

On Tue, Oct 25, 2016 at 3:58 PM, Anuj Phogat <anuj.phogat@gmail.com> wrote:
> In a situation when there are multiple render targets with alpha testing
> enabled, if fragment shader doesn't write to draw buffer zero, alpha
> value used for alpha testing will be undefined. Such case should not
> cause a GPU hang.
>
> Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
> ---
>  tests/all.py                                       |   1 +
>  tests/fbo/CMakeLists.gl.txt                        |   1 +
>  tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c | 145 +++++++++++++++++++++
>  3 files changed, 147 insertions(+)
>  create mode 100644 tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>
> diff --git a/tests/all.py b/tests/all.py
> index 9b67bae..9e4420e 100644
> --- a/tests/all.py
> +++ b/tests/all.py
> @@ -4196,6 +4196,7 @@ with profile.group_manager(
>          grouptools.join('spec', 'arb_draw_buffers')) as g:
>      g(['arb_draw_buffers-state_change'], run_concurrent=False)
>      g(['fbo-mrt-alphatest'], run_concurrent=False)
> +    g(['fbo-mrt-alphatest-no-buffer-zero-write'], run_concurrent=False)
>      g(['fbo-mrt-new-bind'], run_concurrent=False)
>
>  with profile.group_manager(
> diff --git a/tests/fbo/CMakeLists.gl.txt b/tests/fbo/CMakeLists.gl.txt
> index 2e2cac9..e2c03ca 100644
> --- a/tests/fbo/CMakeLists.gl.txt
> +++ b/tests/fbo/CMakeLists.gl.txt
> @@ -73,6 +73,7 @@ piglit_add_executable (fbo-integer fbo-integer.c)
>  piglit_add_executable (fbo-maxsize fbo-maxsize.c)
>  piglit_add_executable (fbo-mipmap-copypix fbo-mipmap-copypix.c)
>  piglit_add_executable (fbo-mrt-alphatest fbo-mrt-alphatest.c)
> +piglit_add_executable (fbo-mrt-alphatest-no-buffer-zero-write fbo-mrt-alphatest-no-buffer-zero-write.c)
>  piglit_add_executable (fbo-mrt-new-bind fbo-mrt-new-bind.c)
>  piglit_add_executable (fbo-nodepth-test fbo-nodepth-test.c)
>  piglit_add_executable (fbo-nostencil-test fbo-nostencil-test.c)
> diff --git a/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
> new file mode 100644
> index 0000000..ef56d89
> --- /dev/null
> +++ b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
> @@ -0,0 +1,145 @@
> +/*
> + * Copyright © 2016 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + */
> +
> +/*
> + * This test asserts correct behavior for alpha-testing of fragments when
> + * multiple color buffers are being rendered to. In particular, the alpha
> + * component of the color output to draw buffer zero is used for the alpha
> + * test. If draw buffer zero is not written by the fragment shader, alpha
> + * value used for alpha testing is undefined. This test should run to
> + * completion without a GPU hang.
> + *
> + * This is important for deferred renderers which use alpha-test, and is a
> + * significant edge case for the i965 driver.
> + */
> +
> +#include "piglit-util-gl.h"
> +
> +PIGLIT_GL_TEST_CONFIG_BEGIN
> +
> +       config.supports_gl_compat_version = 21;
> +
> +       config.window_visual = PIGLIT_GL_VISUAL_RGBA | PIGLIT_GL_VISUAL_DOUBLE;
> +
> +PIGLIT_GL_TEST_CONFIG_END
> +
> +GLenum buffers[] = {GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2};
> +GLuint fbo;
> +GLint prog;
> +GLuint color0, color1, color2;
> +
> +void
> +piglit_init(int argc, char **argv)
> +{
> +       piglit_require_GLSL_version(130);
> +
> +       glGenFramebuffers(1, &fbo);
> +       glBindFramebuffer(GL_FRAMEBUFFER, fbo);
> +
> +       glGenTextures(1, &color0);
> +       glBindTexture(GL_TEXTURE_2D, color0);
> +       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
> +       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
> +       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
> +       glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, color0, 0);
This should be GL_COLOR_ATTACHMENT0. Fixed locally.
> +
> +       glGenTextures(1, &color1);
> +       glBindTexture(GL_TEXTURE_2D, color1);
> +       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
> +       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
> +       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
> +       glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, color1, 0);
> +
> +       glGenTextures(1, &color2);
> +       glBindTexture(GL_TEXTURE_2D, color2);
> +       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
> +       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
> +       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
> +       glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_2D, color2, 0);
> +
> +       glDrawBuffers(3, buffers);
> +
> +       prog = piglit_build_simple_program(
> +               "#version 130\n"
> +               "in vec4 pos;\n"
> +               "void main() {\n"
> +               "       gl_Position = pos;\n"
> +               "}\n",
> +
> +               "#version 130\n"
> +               "void main() {\n"
> +               "       float alpha = float(int(gl_FragCoord.x / 16 + gl_FragCoord.y / 16) % 2);\n"
> +               "       /*Don't write color to draw buffer zero i.e. gl_FragData[0] */\n"
> +               "       gl_FragData[1] = vec4(1.0, 0.0, 0.0, alpha);\n"
> +               "       gl_FragData[2] = vec4(0.0, 1.0, 0.0, 1.0);\n"
> +               "}\n"
> +               );
> +
> +       if (!piglit_check_gl_error(GL_NO_ERROR)) {
> +               printf("Setup for test failed.\n");
> +               piglit_report_result(PIGLIT_SKIP);
> +       }
> +
> +       if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
> +               printf("Framebuffer not complete.\n");
> +               piglit_report_result(PIGLIT_SKIP);
> +       }
> +}
> +
> +
> +enum piglit_result
> +piglit_display(void)
> +{
> +       glBindFramebuffer(GL_FRAMEBUFFER, fbo);
> +       glClearColor(0,0,1,0);
> +       glClear(GL_COLOR_BUFFER_BIT);
> +
> +       glAlphaFunc(GL_GEQUAL, 0.5f);
> +       glEnable(GL_ALPHA_TEST);
> +
> +       glUseProgram(prog);
> +       glViewport(0, 0, 64, 64);
> +       piglit_draw_rect(-1, -1, 2, 2);
> +
> +       glDisable(GL_ALPHA_TEST);
> +
> +       /* Visualize it */
> +       glUseProgram(0);
> +       glBindFramebuffer(GL_FRAMEBUFFER, piglit_winsys_fbo);
> +       glViewport(0, 0, 128, 64);
> +       glClearColor(0,0,0.5,0);
> +       glClear(GL_COLOR_BUFFER_BIT);
> +
> +       glEnable(GL_TEXTURE_2D);
> +       glBindTexture(GL_TEXTURE_2D, color1);
> +       piglit_draw_rect_tex(-1, -1, 1, 2,
> +                       0, 0, 1, 1);
> +       glBindTexture(GL_TEXTURE_2D, color2);
> +       piglit_draw_rect_tex(0, -1, 1, 2,
> +                       0, 0, 1, 1);
> +       glDisable(GL_TEXTURE_2D);
> +       piglit_present_results();
> +
> +       /* If test executes to completion, return PIGLIT_PASS */
> +       return PIGLIT_PASS;
> +}
> --
> 2.5.5
>
On 10/25/2016 03:58 PM, Anuj Phogat wrote:
> In a situation when there are multiple render targets with alpha testing
> enabled, if fragment shader doesn't write to draw buffer zero, alpha
> value used for alpha testing will be undefined. Such case should not
> cause a GPU hang.
>
> Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
> ---
>   tests/all.py                                       |   1 +
>   tests/fbo/CMakeLists.gl.txt                        |   1 +
>   tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c | 145 +++++++++++++++++++++

I think we're trying to get away from putting new tests in general/, 
bugs/, fbo/, etc.

How about tests/spec/gl-2.1/fbo-mrt-alphatest-no-buffer-zero-write.c ?

-Brian


>   3 files changed, 147 insertions(+)
>   create mode 100644 tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>
> diff --git a/tests/all.py b/tests/all.py
> index 9b67bae..9e4420e 100644
> --- a/tests/all.py
> +++ b/tests/all.py
> @@ -4196,6 +4196,7 @@ with profile.group_manager(
>           grouptools.join('spec', 'arb_draw_buffers')) as g:
>       g(['arb_draw_buffers-state_change'], run_concurrent=False)
>       g(['fbo-mrt-alphatest'], run_concurrent=False)
> +    g(['fbo-mrt-alphatest-no-buffer-zero-write'], run_concurrent=False)
>       g(['fbo-mrt-new-bind'], run_concurrent=False)
>
>   with profile.group_manager(
> diff --git a/tests/fbo/CMakeLists.gl.txt b/tests/fbo/CMakeLists.gl.txt
> index 2e2cac9..e2c03ca 100644
> --- a/tests/fbo/CMakeLists.gl.txt
> +++ b/tests/fbo/CMakeLists.gl.txt
> @@ -73,6 +73,7 @@ piglit_add_executable (fbo-integer fbo-integer.c)
>   piglit_add_executable (fbo-maxsize fbo-maxsize.c)
>   piglit_add_executable (fbo-mipmap-copypix fbo-mipmap-copypix.c)
>   piglit_add_executable (fbo-mrt-alphatest fbo-mrt-alphatest.c)
> +piglit_add_executable (fbo-mrt-alphatest-no-buffer-zero-write fbo-mrt-alphatest-no-buffer-zero-write.c)
>   piglit_add_executable (fbo-mrt-new-bind fbo-mrt-new-bind.c)
>   piglit_add_executable (fbo-nodepth-test fbo-nodepth-test.c)
>   piglit_add_executable (fbo-nostencil-test fbo-nostencil-test.c)
> diff --git a/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
> new file mode 100644
> index 0000000..ef56d89
> --- /dev/null
> +++ b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
> @@ -0,0 +1,145 @@
> +/*
> + * Copyright © 2016 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + */
> +
> +/*
> + * This test asserts correct behavior for alpha-testing of fragments when
> + * multiple color buffers are being rendered to. In particular, the alpha
> + * component of the color output to draw buffer zero is used for the alpha
> + * test. If draw buffer zero is not written by the fragment shader, alpha
> + * value used for alpha testing is undefined. This test should run to
> + * completion without a GPU hang.
> + *
> + * This is important for deferred renderers which use alpha-test, and is a
> + * significant edge case for the i965 driver.
> + */

Where in the GL 2.1 spec does it describe this (the undefined behavior, 
that is)?  I took a quick look and didn't see it in the "4.1.4 Alpha 
Test" section.  Can you add a spec quotation?


> +
> +#include "piglit-util-gl.h"
> +
> +PIGLIT_GL_TEST_CONFIG_BEGIN
> +
> +	config.supports_gl_compat_version = 21;
> +
> +	config.window_visual = PIGLIT_GL_VISUAL_RGBA | PIGLIT_GL_VISUAL_DOUBLE;
> +
> +PIGLIT_GL_TEST_CONFIG_END
> +
> +GLenum buffers[] = {GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2};
> +GLuint fbo;
> +GLint prog;
> +GLuint color0, color1, color2;
> +
> +void
> +piglit_init(int argc, char **argv)
> +{
> +	piglit_require_GLSL_version(130);
> +
> +	glGenFramebuffers(1, &fbo);
> +	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
> +
> +	glGenTextures(1, &color0);
> +	glBindTexture(GL_TEXTURE_2D, color0);
> +	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
> +	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, color0, 0);
> +
> +	glGenTextures(1, &color1);
> +	glBindTexture(GL_TEXTURE_2D, color1);
> +	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
> +	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, color1, 0);
> +
> +	glGenTextures(1, &color2);
> +	glBindTexture(GL_TEXTURE_2D, color2);
> +	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
> +	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
> +	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_2D, color2, 0);
> +
> +	glDrawBuffers(3, buffers);
> +
> +	prog = piglit_build_simple_program(
> +		"#version 130\n"
> +		"in vec4 pos;\n"
> +		"void main() {\n"
> +		"	gl_Position = pos;\n"
> +		"}\n",
> +
> +		"#version 130\n"
> +		"void main() {\n"
> +		"	float alpha = float(int(gl_FragCoord.x / 16 + gl_FragCoord.y / 16) % 2);\n"
> +		"	/*Don't write color to draw buffer zero i.e. gl_FragData[0] */\n"
> +		"	gl_FragData[1] = vec4(1.0, 0.0, 0.0, alpha);\n"
> +		"	gl_FragData[2] = vec4(0.0, 1.0, 0.0, 1.0);\n"
> +		"}\n"
> +		);
> +
> +	if (!piglit_check_gl_error(GL_NO_ERROR)) {
> +		printf("Setup for test failed.\n");
> +		piglit_report_result(PIGLIT_SKIP);
> +	}
> +
> +	if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
> +		printf("Framebuffer not complete.\n");
> +		piglit_report_result(PIGLIT_SKIP);
> +	}
> +}
> +
> +
> +enum piglit_result
> +piglit_display(void)
> +{
> +	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
> +	glClearColor(0,0,1,0);
> +	glClear(GL_COLOR_BUFFER_BIT);
> +
> +	glAlphaFunc(GL_GEQUAL, 0.5f);
> +	glEnable(GL_ALPHA_TEST);
> +
> +	glUseProgram(prog);
> +	glViewport(0, 0, 64, 64);
> +	piglit_draw_rect(-1, -1, 2, 2);
> +
> +	glDisable(GL_ALPHA_TEST);
> +
> +	/* Visualize it */
> +	glUseProgram(0);
> +	glBindFramebuffer(GL_FRAMEBUFFER, piglit_winsys_fbo);
> +	glViewport(0, 0, 128, 64);
> +	glClearColor(0,0,0.5,0);
> +	glClear(GL_COLOR_BUFFER_BIT);
> +
> +	glEnable(GL_TEXTURE_2D);
> +	glBindTexture(GL_TEXTURE_2D, color1);
> +	piglit_draw_rect_tex(-1, -1, 1, 2,
> +			0, 0, 1, 1);
> +	glBindTexture(GL_TEXTURE_2D, color2);
> +	piglit_draw_rect_tex(0, -1, 1, 2,
> +			0, 0, 1, 1);
> +	glDisable(GL_TEXTURE_2D);
> +	piglit_present_results();

If behavior is undefined, I guess we can't probe any pixels for any 
thing.  Maybe put a comment here to that effect.

> +
> +	/* If test executes to completion, return PIGLIT_PASS */
> +	return PIGLIT_PASS;
> +}
>

Looks good otherwise.

-Brian
On 10/26/2016 03:05 AM, Brian Paul wrote:
> On 10/25/2016 03:58 PM, Anuj Phogat wrote:
>> In a situation when there are multiple render targets with alpha testing
>> enabled, if fragment shader doesn't write to draw buffer zero, alpha
>> value used for alpha testing will be undefined. Such case should not
>> cause a GPU hang.
>>
>> Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
>> ---
>>   tests/all.py                                       |   1 +
>>   tests/fbo/CMakeLists.gl.txt                        |   1 +
>>   tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c | 145
>> +++++++++++++++++++++
>
> I think we're trying to get away from putting new tests in general/,
> bugs/, fbo/, etc.
>
> How about tests/spec/gl-2.1/fbo-mrt-alphatest-no-buffer-zero-write.c ?
>
> -Brian
>
>
>>   3 files changed, 147 insertions(+)
>>   create mode 100644 tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>>
>> diff --git a/tests/all.py b/tests/all.py
>> index 9b67bae..9e4420e 100644
>> --- a/tests/all.py
>> +++ b/tests/all.py
>> @@ -4196,6 +4196,7 @@ with profile.group_manager(
>>           grouptools.join('spec', 'arb_draw_buffers')) as g:
>>       g(['arb_draw_buffers-state_change'], run_concurrent=False)
>>       g(['fbo-mrt-alphatest'], run_concurrent=False)
>> +    g(['fbo-mrt-alphatest-no-buffer-zero-write'], run_concurrent=False)
>>       g(['fbo-mrt-new-bind'], run_concurrent=False)
>>
>>   with profile.group_manager(
>> diff --git a/tests/fbo/CMakeLists.gl.txt b/tests/fbo/CMakeLists.gl.txt
>> index 2e2cac9..e2c03ca 100644
>> --- a/tests/fbo/CMakeLists.gl.txt
>> +++ b/tests/fbo/CMakeLists.gl.txt
>> @@ -73,6 +73,7 @@ piglit_add_executable (fbo-integer fbo-integer.c)
>>   piglit_add_executable (fbo-maxsize fbo-maxsize.c)
>>   piglit_add_executable (fbo-mipmap-copypix fbo-mipmap-copypix.c)
>>   piglit_add_executable (fbo-mrt-alphatest fbo-mrt-alphatest.c)
>> +piglit_add_executable (fbo-mrt-alphatest-no-buffer-zero-write
>> fbo-mrt-alphatest-no-buffer-zero-write.c)
>>   piglit_add_executable (fbo-mrt-new-bind fbo-mrt-new-bind.c)
>>   piglit_add_executable (fbo-nodepth-test fbo-nodepth-test.c)
>>   piglit_add_executable (fbo-nostencil-test fbo-nostencil-test.c)
>> diff --git a/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>> b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>> new file mode 100644
>> index 0000000..ef56d89
>> --- /dev/null
>> +++ b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>> @@ -0,0 +1,145 @@
>> +/*
>> + * Copyright © 2016 Intel Corporation
>> + *
>> + * Permission is hereby granted, free of charge, to any person
>> obtaining a
>> + * copy of this software and associated documentation files (the
>> "Software"),
>> + * to deal in the Software without restriction, including without
>> limitation
>> + * the rights to use, copy, modify, merge, publish, distribute,
>> sublicense,
>> + * and/or sell copies of the Software, and to permit persons to whom the
>> + * Software is furnished to do so, subject to the following conditions:
>> + *
>> + * The above copyright notice and this permission notice (including
>> the next
>> + * paragraph) shall be included in all copies or substantial portions
>> of the
>> + * Software.
>> + *
>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
>> EXPRESS OR
>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
>> MERCHANTABILITY,
>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT
>> SHALL
>> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
>> OR OTHER
>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
>> ARISING
>> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
>> OTHER DEALINGS
>> + * IN THE SOFTWARE.
>> + */
>> +
>> +/*
>> + * This test asserts correct behavior for alpha-testing of fragments
>> when
>> + * multiple color buffers are being rendered to. In particular, the
>> alpha
>> + * component of the color output to draw buffer zero is used for the
>> alpha
>> + * test. If draw buffer zero is not written by the fragment shader,
>> alpha
>> + * value used for alpha testing is undefined. This test should run to
>> + * completion without a GPU hang.
>> + *
>> + * This is important for deferred renderers which use alpha-test, and
>> is a
>> + * significant edge case for the i965 driver.
>> + */
>
> Where in the GL 2.1 spec does it describe this (the undefined behavior,
> that is)?  I took a quick look and didn't see it in the "4.1.4 Alpha
> Test" section.  Can you add a spec quotation?

Maybe this? (4.2.1):

"If a fragment shader writes to neither gl FragColor nor gl FragData, 
the values of the fragment colors following shader execution are 
undefined, and may differ for each fragment color."

I believe we've actually had earlier bug where MRT shader did not write 
anything to one of its outputs but I can't find it now.


>
>> +
>> +#include "piglit-util-gl.h"
>> +
>> +PIGLIT_GL_TEST_CONFIG_BEGIN
>> +
>> +    config.supports_gl_compat_version = 21;
>> +
>> +    config.window_visual = PIGLIT_GL_VISUAL_RGBA |
>> PIGLIT_GL_VISUAL_DOUBLE;
>> +
>> +PIGLIT_GL_TEST_CONFIG_END
>> +
>> +GLenum buffers[] = {GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1,
>> GL_COLOR_ATTACHMENT2};
>> +GLuint fbo;
>> +GLint prog;
>> +GLuint color0, color1, color2;
>> +
>> +void
>> +piglit_init(int argc, char **argv)
>> +{
>> +    piglit_require_GLSL_version(130);
>> +
>> +    glGenFramebuffers(1, &fbo);
>> +    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
>> +
>> +    glGenTextures(1, &color0);
>> +    glBindTexture(GL_TEXTURE_2D, color0);
>> +    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA,
>> GL_UNSIGNED_BYTE, NULL);
>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
>> +    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1,
>> GL_TEXTURE_2D, color0, 0);
>> +
>> +    glGenTextures(1, &color1);
>> +    glBindTexture(GL_TEXTURE_2D, color1);
>> +    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA,
>> GL_UNSIGNED_BYTE, NULL);
>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
>> +    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1,
>> GL_TEXTURE_2D, color1, 0);
>> +
>> +    glGenTextures(1, &color2);
>> +    glBindTexture(GL_TEXTURE_2D, color2);
>> +    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA,
>> GL_UNSIGNED_BYTE, NULL);
>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
>> +    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2,
>> GL_TEXTURE_2D, color2, 0);
>> +
>> +    glDrawBuffers(3, buffers);
>> +
>> +    prog = piglit_build_simple_program(
>> +        "#version 130\n"
>> +        "in vec4 pos;\n"
>> +        "void main() {\n"
>> +        "    gl_Position = pos;\n"
>> +        "}\n",
>> +
>> +        "#version 130\n"
>> +        "void main() {\n"
>> +        "    float alpha = float(int(gl_FragCoord.x / 16 +
>> gl_FragCoord.y / 16) % 2);\n"
>> +        "    /*Don't write color to draw buffer zero i.e.
>> gl_FragData[0] */\n"
>> +        "    gl_FragData[1] = vec4(1.0, 0.0, 0.0, alpha);\n"
>> +        "    gl_FragData[2] = vec4(0.0, 1.0, 0.0, 1.0);\n"
>> +        "}\n"
>> +        );
>> +
>> +    if (!piglit_check_gl_error(GL_NO_ERROR)) {
>> +        printf("Setup for test failed.\n");
>> +        piglit_report_result(PIGLIT_SKIP);
>> +    }
>> +
>> +    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) !=
>> GL_FRAMEBUFFER_COMPLETE) {
>> +        printf("Framebuffer not complete.\n");
>> +        piglit_report_result(PIGLIT_SKIP);
>> +    }
>> +}
>> +
>> +
>> +enum piglit_result
>> +piglit_display(void)
>> +{
>> +    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
>> +    glClearColor(0,0,1,0);
>> +    glClear(GL_COLOR_BUFFER_BIT);
>> +
>> +    glAlphaFunc(GL_GEQUAL, 0.5f);
>> +    glEnable(GL_ALPHA_TEST);
>> +
>> +    glUseProgram(prog);
>> +    glViewport(0, 0, 64, 64);
>> +    piglit_draw_rect(-1, -1, 2, 2);
>> +
>> +    glDisable(GL_ALPHA_TEST);
>> +
>> +    /* Visualize it */
>> +    glUseProgram(0);
>> +    glBindFramebuffer(GL_FRAMEBUFFER, piglit_winsys_fbo);
>> +    glViewport(0, 0, 128, 64);
>> +    glClearColor(0,0,0.5,0);
>> +    glClear(GL_COLOR_BUFFER_BIT);
>> +
>> +    glEnable(GL_TEXTURE_2D);
>> +    glBindTexture(GL_TEXTURE_2D, color1);
>> +    piglit_draw_rect_tex(-1, -1, 1, 2,
>> +            0, 0, 1, 1);
>> +    glBindTexture(GL_TEXTURE_2D, color2);
>> +    piglit_draw_rect_tex(0, -1, 1, 2,
>> +            0, 0, 1, 1);
>> +    glDisable(GL_TEXTURE_2D);
>> +    piglit_present_results();
>
> If behavior is undefined, I guess we can't probe any pixels for any
> thing.  Maybe put a comment here to that effect.
>
>> +
>> +    /* If test executes to completion, return PIGLIT_PASS */
>> +    return PIGLIT_PASS;
>> +}
>>
>
> Looks good otherwise.
>
> -Brian
>
> _______________________________________________
> Piglit mailing list
> Piglit@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/piglit
On Tue, Oct 25, 2016 at 10:34 PM, Tapani Pälli <tapani.palli@intel.com> wrote:
>
>
> On 10/26/2016 03:05 AM, Brian Paul wrote:
>>
>> On 10/25/2016 03:58 PM, Anuj Phogat wrote:
>>>
>>> In a situation when there are multiple render targets with alpha testing
>>> enabled, if fragment shader doesn't write to draw buffer zero, alpha
>>> value used for alpha testing will be undefined. Such case should not
>>> cause a GPU hang.
>>>
>>> Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
>>> ---
>>>   tests/all.py                                       |   1 +
>>>   tests/fbo/CMakeLists.gl.txt                        |   1 +
>>>   tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c | 145
>>> +++++++++++++++++++++
>>
>>
>> I think we're trying to get away from putting new tests in general/,
>> bugs/, fbo/, etc.
>>
>> How about tests/spec/gl-2.1/fbo-mrt-alphatest-no-buffer-zero-write.c ?
sounds good to me.

>>
>> -Brian
>>
>>
>>>   3 files changed, 147 insertions(+)
>>>   create mode 100644 tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>>>
>>> diff --git a/tests/all.py b/tests/all.py
>>> index 9b67bae..9e4420e 100644
>>> --- a/tests/all.py
>>> +++ b/tests/all.py
>>> @@ -4196,6 +4196,7 @@ with profile.group_manager(
>>>           grouptools.join('spec', 'arb_draw_buffers')) as g:
>>>       g(['arb_draw_buffers-state_change'], run_concurrent=False)
>>>       g(['fbo-mrt-alphatest'], run_concurrent=False)
>>> +    g(['fbo-mrt-alphatest-no-buffer-zero-write'], run_concurrent=False)
>>>       g(['fbo-mrt-new-bind'], run_concurrent=False)
>>>
>>>   with profile.group_manager(
>>> diff --git a/tests/fbo/CMakeLists.gl.txt b/tests/fbo/CMakeLists.gl.txt
>>> index 2e2cac9..e2c03ca 100644
>>> --- a/tests/fbo/CMakeLists.gl.txt
>>> +++ b/tests/fbo/CMakeLists.gl.txt
>>> @@ -73,6 +73,7 @@ piglit_add_executable (fbo-integer fbo-integer.c)
>>>   piglit_add_executable (fbo-maxsize fbo-maxsize.c)
>>>   piglit_add_executable (fbo-mipmap-copypix fbo-mipmap-copypix.c)
>>>   piglit_add_executable (fbo-mrt-alphatest fbo-mrt-alphatest.c)
>>> +piglit_add_executable (fbo-mrt-alphatest-no-buffer-zero-write
>>> fbo-mrt-alphatest-no-buffer-zero-write.c)
>>>   piglit_add_executable (fbo-mrt-new-bind fbo-mrt-new-bind.c)
>>>   piglit_add_executable (fbo-nodepth-test fbo-nodepth-test.c)
>>>   piglit_add_executable (fbo-nostencil-test fbo-nostencil-test.c)
>>> diff --git a/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>>> b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>>> new file mode 100644
>>> index 0000000..ef56d89
>>> --- /dev/null
>>> +++ b/tests/fbo/fbo-mrt-alphatest-no-buffer-zero-write.c
>>> @@ -0,0 +1,145 @@
>>> +/*
>>> + * Copyright © 2016 Intel Corporation
>>> + *
>>> + * Permission is hereby granted, free of charge, to any person
>>> obtaining a
>>> + * copy of this software and associated documentation files (the
>>> "Software"),
>>> + * to deal in the Software without restriction, including without
>>> limitation
>>> + * the rights to use, copy, modify, merge, publish, distribute,
>>> sublicense,
>>> + * and/or sell copies of the Software, and to permit persons to whom the
>>> + * Software is furnished to do so, subject to the following conditions:
>>> + *
>>> + * The above copyright notice and this permission notice (including
>>> the next
>>> + * paragraph) shall be included in all copies or substantial portions
>>> of the
>>> + * Software.
>>> + *
>>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
>>> EXPRESS OR
>>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
>>> MERCHANTABILITY,
>>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT
>>> SHALL
>>> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
>>> OR OTHER
>>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
>>> ARISING
>>> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
>>> OTHER DEALINGS
>>> + * IN THE SOFTWARE.
>>> + */
>>> +
>>> +/*
>>> + * This test asserts correct behavior for alpha-testing of fragments
>>> when
>>> + * multiple color buffers are being rendered to. In particular, the
>>> alpha
>>> + * component of the color output to draw buffer zero is used for the
>>> alpha
>>> + * test. If draw buffer zero is not written by the fragment shader,
>>> alpha
>>> + * value used for alpha testing is undefined. This test should run to
>>> + * completion without a GPU hang.
>>> + *
>>> + * This is important for deferred renderers which use alpha-test, and
>>> is a
>>> + * significant edge case for the i965 driver.
>>> + */
>>
>>
>> Where in the GL 2.1 spec does it describe this (the undefined behavior,
>> that is)?  I took a quick look and didn't see it in the "4.1.4 Alpha
>> Test" section.  Can you add a spec quotation?
>
>
> Maybe this? (4.2.1):
>
> "If a fragment shader writes to neither gl FragColor nor gl FragData, the
> values of the fragment colors following shader execution are undefined, and
> may differ for each fragment color."
>
I'll add this reference in a comment. ARB_draw_buffers has similar
mention for MRTs.

> I believe we've actually had earlier bug where MRT shader did not write
> anything to one of its outputs but I can't find it now.
>
>
>>
>>> +
>>> +#include "piglit-util-gl.h"
>>> +
>>> +PIGLIT_GL_TEST_CONFIG_BEGIN
>>> +
>>> +    config.supports_gl_compat_version = 21;
>>> +
>>> +    config.window_visual = PIGLIT_GL_VISUAL_RGBA |
>>> PIGLIT_GL_VISUAL_DOUBLE;
>>> +
>>> +PIGLIT_GL_TEST_CONFIG_END
>>> +
>>> +GLenum buffers[] = {GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1,
>>> GL_COLOR_ATTACHMENT2};
>>> +GLuint fbo;
>>> +GLint prog;
>>> +GLuint color0, color1, color2;
>>> +
>>> +void
>>> +piglit_init(int argc, char **argv)
>>> +{
>>> +    piglit_require_GLSL_version(130);
>>> +
>>> +    glGenFramebuffers(1, &fbo);
>>> +    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
>>> +
>>> +    glGenTextures(1, &color0);
>>> +    glBindTexture(GL_TEXTURE_2D, color0);
>>> +    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA,
>>> GL_UNSIGNED_BYTE, NULL);
>>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
>>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
>>> +    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1,
>>> GL_TEXTURE_2D, color0, 0);
>>> +
>>> +    glGenTextures(1, &color1);
>>> +    glBindTexture(GL_TEXTURE_2D, color1);
>>> +    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA,
>>> GL_UNSIGNED_BYTE, NULL);
>>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
>>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
>>> +    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1,
>>> GL_TEXTURE_2D, color1, 0);
>>> +
>>> +    glGenTextures(1, &color2);
>>> +    glBindTexture(GL_TEXTURE_2D, color2);
>>> +    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA,
>>> GL_UNSIGNED_BYTE, NULL);
>>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
>>> +    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
>>> +    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2,
>>> GL_TEXTURE_2D, color2, 0);
>>> +
>>> +    glDrawBuffers(3, buffers);
>>> +
>>> +    prog = piglit_build_simple_program(
>>> +        "#version 130\n"
>>> +        "in vec4 pos;\n"
>>> +        "void main() {\n"
>>> +        "    gl_Position = pos;\n"
>>> +        "}\n",
>>> +
>>> +        "#version 130\n"
>>> +        "void main() {\n"
>>> +        "    float alpha = float(int(gl_FragCoord.x / 16 +
>>> gl_FragCoord.y / 16) % 2);\n"
>>> +        "    /*Don't write color to draw buffer zero i.e.
>>> gl_FragData[0] */\n"
>>> +        "    gl_FragData[1] = vec4(1.0, 0.0, 0.0, alpha);\n"
>>> +        "    gl_FragData[2] = vec4(0.0, 1.0, 0.0, 1.0);\n"
>>> +        "}\n"
>>> +        );
>>> +
>>> +    if (!piglit_check_gl_error(GL_NO_ERROR)) {
>>> +        printf("Setup for test failed.\n");
>>> +        piglit_report_result(PIGLIT_SKIP);
>>> +    }
>>> +
>>> +    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) !=
>>> GL_FRAMEBUFFER_COMPLETE) {
>>> +        printf("Framebuffer not complete.\n");
>>> +        piglit_report_result(PIGLIT_SKIP);
>>> +    }
>>> +}
>>> +
>>> +
>>> +enum piglit_result
>>> +piglit_display(void)
>>> +{
>>> +    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
>>> +    glClearColor(0,0,1,0);
>>> +    glClear(GL_COLOR_BUFFER_BIT);
>>> +
>>> +    glAlphaFunc(GL_GEQUAL, 0.5f);
>>> +    glEnable(GL_ALPHA_TEST);
>>> +
>>> +    glUseProgram(prog);
>>> +    glViewport(0, 0, 64, 64);
>>> +    piglit_draw_rect(-1, -1, 2, 2);
>>> +
>>> +    glDisable(GL_ALPHA_TEST);
>>> +
>>> +    /* Visualize it */
>>> +    glUseProgram(0);
>>> +    glBindFramebuffer(GL_FRAMEBUFFER, piglit_winsys_fbo);
>>> +    glViewport(0, 0, 128, 64);
>>> +    glClearColor(0,0,0.5,0);
>>> +    glClear(GL_COLOR_BUFFER_BIT);
>>> +
>>> +    glEnable(GL_TEXTURE_2D);
>>> +    glBindTexture(GL_TEXTURE_2D, color1);
>>> +    piglit_draw_rect_tex(-1, -1, 1, 2,
>>> +            0, 0, 1, 1);
>>> +    glBindTexture(GL_TEXTURE_2D, color2);
>>> +    piglit_draw_rect_tex(0, -1, 1, 2,
>>> +            0, 0, 1, 1);
>>> +    glDisable(GL_TEXTURE_2D);
>>> +    piglit_present_results();
>>
>>
>> If behavior is undefined, I guess we can't probe any pixels for any
>> thing.  Maybe put a comment here to that effect.
>>
I'll add a comment here.
>>> +
>>> +    /* If test executes to completion, return PIGLIT_PASS */
>>> +    return PIGLIT_PASS;
>>> +}
>>>
>>
>> Looks good otherwise.
>>
>> -Brian
>>
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