[Mesa-dev] [PATCH-RFC] draw: Rewrite primitive decomposer

[Zack Rusin]

On Tuesday 03 August 2010 12:56:41 Chia-I Wu wrote:
> I see your point.  There are more than one way to interpret the
> diagram.  Now I am curious if the diagram is all the D3D documents have
> for triangle strip with adjacency?

As far as the public docs go I think that's it.

> > and so on. If you have a testcase that shows  which way it is, great,
> > lets change it (aka fix it). Otherwise I'm just not too excited about
> > changing code that was working with the (corny) testcases it had for
> > something without any.
> 
> Sure.  Where can I find the test cases, if they are public?

I've tested with a few proprietary demos/apps, but since I've implemented gs 
in Mesa as well we can use that. You can put the attached files in 
demos/src/glsl and compile it there. I never tested triangle strips with 
adjacency in mesa but it seems to be at least rendering something (the 
adjacency vertices are definitely flipped). Try glDrawArrays with different 
values, e.g.
1) glDrawArrays(GL_TRIANGLE_STRIP_ADJACENCY_ARB, 0, 6);
2) glDrawArrays(GL_TRIANGLE_STRIP_ADJACENCY_ARB, 2, 6);
3) glDrawArrays(GL_TRIANGLE_STRIP_ADJACENCY_ARB, 4, 6);
4) glDrawArrays(GL_TRIANGLE_STRIP_ADJACENCY_ARB, 0, 8);
5) glDrawArrays(GL_TRIANGLE_STRIP_ADJACENCY_ARB, 2, 8);
6) glDrawArrays(GL_TRIANGLE_STRIP_ADJACENCY_ARB, 0, 10);

It'd be awesome if we had a piglit test for it, but right now anything that 
with some manual testing looks like whatever proprietary NVIDIA/AMD drivers do 
would be fine.

z
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#version 120
#extension GL_EXT_geometry_shader4: enable


void main()
{

    gl_Position = gl_PositionIn[1];
    gl_FrontColor = vec4(1, 0, 0, 0.5);
    EmitVertex();
    gl_Position = gl_PositionIn[3];
    gl_FrontColor = vec4(0, 1, 0, 0.5);
    EmitVertex();
    gl_Position = gl_PositionIn[5];
    gl_FrontColor = vec4(0, 0, 1, 0.5);
    EmitVertex();
    EndPrimitive();

    gl_Position = gl_PositionIn[0];
    gl_FrontColor = vec4(1, 1, 1, 1);
    EmitVertex();
    gl_Position = gl_PositionIn[2];
    gl_FrontColor = vec4(1, 0, 0, 1);
    EmitVertex();
    gl_Position = gl_PositionIn[4];
    gl_FrontColor = vec4(0, 0, 1, 1);
    EmitVertex();
    EndPrimitive();
}