4 // require_extensions: GL_ARB_tessellation_shader
8 #extension GL_ARB_tessellation_shader: require
10 layout(vertices = 3) out;
13 /* If a per-vertex output variable is used as an l-value, it is an
14 * error if the expression indicating the vertex number is not the
15 * identifier "gl_InvocationID".
17 * This test interprets the requirement strictly -- even though `n`
18 * will take the correct value, this is not allowed.
23 int n = gl_InvocationID;