[Piglit] [PATCH] gl-1.5-vertex-buffer-offsets: test unusual vertex offsets/strides
Jose Fonseca
jfonseca at vmware.com
Sun Jun 21 01:00:24 PDT 2015
It depends on the platform. But x86 doesn't require floats to be 4-byte aligned. https://en.wikipedia.org/wiki/Data_structure_alignment#x86
I don't know about other platforms though -- it might be indeed necessary to skip or be less strict on non-x86 platforms.
I'm having trouble interpreting the "additional base-level requirement" means. Is it saying that a an offset to a float (4bytes), must be 4bytes aligned, regardless the platform can deal with non- 4-byte aligned floats?
Jose
________________________________________
From: Piglit <piglit-bounces at lists.freedesktop.org> on behalf of Chris Forbes <chrisf at ijw.co.nz>
Sent: 20 June 2015 11:32
To: Brian Paul
Cc: piglit at lists.freedesktop.org
Subject: Re: [Piglit] [PATCH] gl-1.5-vertex-buffer-offsets: test unusual vertex offsets/strides
Brian,
Doesn't this test run afoul of the alignment requirements?
The OpenGL 1.5 specification, page 33 [first version in which this is
introduced;
equivalent language exists in later spec versions] says:
"Clients must align data elements consistent with the requirements of the
client platform, with an additional base-level requirement that an
offset within
a buffer to a datum comprising N basic machine units be a multiple of N."
Non-naturally-aligned float attributes sourced from a buffer object would appear
to violate this rule - or have I misunderstood?
- Chris
On Sat, Jun 20, 2015 at 2:39 AM, Brian Paul <brianp at vmware.com> wrote:
> The draw-vertices tests exercises unusual vertex sizes and strides,
> but not with interleaved arrays.
>
> This test creates a VBO with interleaved vertex positions and colors.
> The colors are positioned at offsets like 9, 10 and 11 bytes from the
> start of the vertex. Unusual strides between vertices are tested too.
>
> Exercises a bug in Gallium's u_vbuf code where the driver was passed
> pipe_vertex_element::src_offset values which weren't a multiple of
> four, even when PIPE_CAP_VERTEX_ELEMENT_SRC_OFFSET_4BYTE_ALIGNED_ONLY
> returned 1.
> ---
> tests/all.py | 1 +
> tests/spec/gl-1.5/CMakeLists.gl.txt | 1 +
> tests/spec/gl-1.5/vertex-buffer-offsets.c | 124 ++++++++++++++++++++++++++++++
> 3 files changed, 126 insertions(+)
> create mode 100644 tests/spec/gl-1.5/vertex-buffer-offsets.c
>
> diff --git a/tests/all.py b/tests/all.py
> index ad4c494..ee11be6 100755
> --- a/tests/all.py
> +++ b/tests/all.py
> @@ -1042,6 +1042,7 @@ with profile.group_manager(
> 'normal3b3s-invariance-byte', run_concurrent=False)
> g(['gl-1.5-normal3b3s-invariance', 'GL_SHORT'],
> 'normal3b3s-invariance-short', run_concurrent=False)
> + g(['gl-1.5-vertex-buffer-offsets'], 'vertex-buffer-offsets')
>
> with profile.group_manager(
> PiglitGLTest,
> diff --git a/tests/spec/gl-1.5/CMakeLists.gl.txt b/tests/spec/gl-1.5/CMakeLists.gl.txt
> index 8dcd95d..f10c6cb 100644
> --- a/tests/spec/gl-1.5/CMakeLists.gl.txt
> +++ b/tests/spec/gl-1.5/CMakeLists.gl.txt
> @@ -10,5 +10,6 @@ link_libraries (
> )
>
> piglit_add_executable (gl-1.5-normal3b3s-invariance normal3b3s-invariance.c)
> +piglit_add_executable (gl-1.5-vertex-buffer-offsets vertex-buffer-offsets.c)
>
> # vim: ft=cmake:
> diff --git a/tests/spec/gl-1.5/vertex-buffer-offsets.c b/tests/spec/gl-1.5/vertex-buffer-offsets.c
> new file mode 100644
> index 0000000..6d58331
> --- /dev/null
> +++ b/tests/spec/gl-1.5/vertex-buffer-offsets.c
> @@ -0,0 +1,124 @@
> +/*
> + * Copyright 2015 VMware, Inc.
> + *
> + * 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.
> + */
> +
> +/*
> + * Test interleaved vertex arrays with unusual element offsets and strides.
> + * Brian Paul
> + */
> +
> +#include "piglit-util-gl.h"
> +
> +PIGLIT_GL_TEST_CONFIG_BEGIN
> + config.supports_gl_compat_version = 15;
> + config.window_visual = PIGLIT_GL_VISUAL_RGBA | PIGLIT_GL_VISUAL_DOUBLE;
> +PIGLIT_GL_TEST_CONFIG_END
> +
> +
> +void
> +piglit_init(int argc, char **argv)
> +{
> + /* nothing */
> +}
> +
> +
> +static bool
> +test_offset_stride(int color_offset, int stride)
> +{
> + static const GLfloat vertex[4][2] = {
> + { -1, -1 },
> + { 1, -1 },
> + { 1, 1 },
> + { -1, 1 }
> + };
> + static const GLfloat color[4] = { 0.0, 1.0, 0.5, 1.0 };
> + GLubyte buffer[1000];
> + GLuint buf;
> + int i, pos;
> + bool p;
> +
> + assert(color_offset >= sizeof(vertex[0]));
> + assert(stride >= color_offset + sizeof(color));
> +
> + pos = 0;
> + for (i = 0; i < 4; i++) {
> + /* copy vertex position into buffer */
> + memcpy(buffer + pos, vertex[i], sizeof(vertex[i]));
> +
> + /* copy vertex color into buffer at unusual offset */
> + memcpy(buffer + pos + color_offset, color, sizeof(color));
> +
> + pos += stride;
> + }
> + assert(pos <= sizeof(buffer));
> +
> + glGenBuffers(1, &buf);
> + glBindBuffer(GL_ARRAY_BUFFER, buf);
> + glBufferData(GL_ARRAY_BUFFER, sizeof(buffer),
> + buffer, GL_STATIC_DRAW);
> +
> + glVertexPointer(2, GL_FLOAT, stride, (void *) 0);
> + glColorPointer(4, GL_FLOAT, stride, (void *) (size_t) color_offset);
> + glEnable(GL_VERTEX_ARRAY);
> + glEnable(GL_COLOR_ARRAY);
> +
> + glClear(GL_COLOR_BUFFER_BIT);
> + glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
> +
> + p = piglit_probe_rect_rgba(0, 0, piglit_width, piglit_height, color);
> +
> + if (!p) {
> + printf("failure for color_offset %d, stride %d\n",
> + color_offset, stride);
> + }
> +
> + piglit_present_results();
> +
> + glDeleteBuffers(1, &buf);
> +
> + return p;
> +}
> +
> +
> +enum piglit_result
> +piglit_display(void)
> +{
> + bool pass = true;
> +
> + /* test nice values */
> + pass = test_offset_stride(8, 24) && pass;
> + pass = test_offset_stride(12, 28) && pass;
> +
> + /* test unual offset */
> + pass = test_offset_stride(9, 32) && pass;
> +
> + /* test unual stride */
> + pass = test_offset_stride(8, 27) && pass;
> +
> + /* test unusual offset, unusual stride */
> + pass = test_offset_stride(9, 25) && pass;
> + pass = test_offset_stride(10, 26) && pass;
> + pass = test_offset_stride(11, 27) && pass;
> +
> + return pass ? PIGLIT_PASS : PIGLIT_FAIL;
> +}
> +
> --
> 1.9.1
>
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