[Piglit] [PATCH] Test case on rendering with only fragment shader but no vertex shader.

[Paul Berry]

On 2 November 2011 02:07, Zhao, Jian J <jian.j.zhao at intel.com> wrote:

> Hi Paul, ****
>
>   Thanks for your suggestion.  My answer is inline. ****
>
> ** **
>
> Best regards****
>
> ZhaoJian****
>
> ** **
>
> *From:* Paul Berry [mailto:stereotype441 at gmail.com]
> *Sent:* Wednesday, November 02, 2011 12:20 AM
> *To:* Zhao, Jian J
> *Cc:* piglit at lists.freedesktop.org
> *Subject:* Re: [Piglit] [PATCH] Test case on rendering with only fragment
> shader but no vertex shader.****
>
> ** **
>
> Before I get to specific comments, are you familiar with Piglit's "shader
> runner" framework (look at any of the Piglit files that end in
> ".shader_test").  It seems like this test could be rewritten as a shader
> runner test--that would make it shorter and more readable, and save a
> compilation step.****
>
> ** **
>
> It’s a good idea. But unfortunately I can’t reproduce it with
> shader_runner, I have a look and find it is because it uses
> glDrawArraysInstancedARB instead of glDrawArrays or just simple glBegin and
> glEnd. I don’t know what is glDrawArraysInstancedARB. What’s it difference
> from glDrawArrays? So I just updated my original patch file. ****
>
>
>
You're right that it doesn't make sense to use
glDrawArraysInstancedARB--that function is only available if your GL
implementation supports the ARB_draw_instanced extension, or GL 3.1, and
there's no good reason to make your test dependent on those.  (If you're
curious, you can find documentation for the extension in
http://www.opengl.org/registry/specs/ARB/draw_instanced.txt.  When the
extension was folded into GL 3.1, it was renamed to glDrawArraysInstanced).

But shader_runner only tries to use glDrawArraysInstancedARB if your
shader_test file contains the command "draw instanced rect".  You should be
able to do the testing you need by just drawing a simple rectangle using
the "draw rect" command, which works on GL 2.1.

For an example of how this sort of test is typically written using
shader_runner, see for instance
tests/spec/glsl-1.10/execution/fs-inline-notequal.shader_test.

Thanks very much for your patience with this--I really want to avoid having
to add more compiled C programs to piglit if at all possible.
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