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# Check proper functioning of the gl_PrimitiveIDIn geometry shader
# input.
[require]
GLSL >= 1.50
[vertex shader]
#version 150
in vec4 vertex;
out int vertex_id_to_gs;
out vec4 vertex_to_gs;
void main()
{
vertex_to_gs = vertex;
vertex_id_to_gs = gl_VertexID;
}
[geometry shader]
#version 150
layout(triangles) in;
layout(triangle_strip, max_vertices = 3) out;
in vec4 vertex_to_gs[3];
in int vertex_id_to_gs[3];
out vec4 color;
void main()
{
/* We draw a triangle fan containing of 6 vertices, so the
* relationship between the primitive ID and the input vertex IDs
* should be:
*
* Primitive ID Vertex ID's
* 0 0 1 2
* 1 0 2 3
* 2 0 3 4
* 3 0 4 5
*
* To avoid relying on the order in which vertices appear within
* each triangle, compute the maximum of the input vertex IDs, and
* subtract 2 from it. That is the expected primitive ID.
*/
int expected_primitive_id =
max(max(vertex_id_to_gs[0], vertex_id_to_gs[1]), vertex_id_to_gs[2]) - 2;
bool ok = expected_primitive_id == gl_PrimitiveIDIn;
for (int i = 0; i < 3; i++) {
gl_Position = vertex_to_gs[i];
color = ok ? vec4(0.0, 1.0, 0.0, 1.0) : vec4(1.0, 0.0, 0.0, 1.0);
EmitVertex();
}
}
[fragment shader]
#version 150
in vec4 color;
void main()
{
gl_FragColor = color;
}
[vertex data]
vertex/float/2
-1.0 -1.0
-1.0 1.0
0.0 1.0
1.0 1.0
1.0 0.0
1.0 -1.0
[test]
clear color 0.0 0.0 0.0 0.0
clear
draw arrays GL_TRIANGLE_FAN 0 6
probe all rgba 0.0 1.0 0.0 1.0
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