OpenGL 3.3 - How to change tesselataionlevel during run time?

Question

How can I change the tesselation leveln during runtime?
My only idea is to create a bufferobject with only one variable, which I have to pass through... Are there any better solutions?

I have a tesselation control shader file which works fine:

[...]
void main()
{
    if(gl_InvocationID==0)
    {
    gl_TessLevelInner[0]= 5.0;
    gl_TessLevelOuter[0]=5.0;
    gl_TessLevelOuter[1]=5.0;
    gl_TessLevelOuter[2]=5.0;
    }
 gl_out[gl_InvocationID].gl_Position =gl_in[gl_InvocationID].gl_Position;
}

You can always pass the tesselation level as a uniform variable. — Jesus Ramos, Aug 06 '14 at 22:22
@Deduplicator This is GLSL, so `void main` is correct (it doesn't return anything). — GuyRT, Aug 07 '14 at 08:21
What do you mean with "int main"? Can you give me an example please? — user3573634, Aug 07 '14 at 09:26
@GuyRT: In that case, it is mistagged with the wrong language. — Deduplicator, Aug 07 '14 at 13:15

score 0 · Answer 1 · answered Aug 07 '14 at 08:31

You can pass the tessellation values as uniforms or (as the values are constant for each draw call) bypass the tessellation control shader altogether. If no TCS is linked to your shader program, the values supplied with -

GLfloat outer_values[4];
GLfloat inner_values[2];
// outer_values and inner_values should be set here
glPatchParameterfv(GL_PATCH_DEFAULT_OUTER_LEVEL, outer_values);
glPatchParameterfv(GL_PATCH_DEFAULT_INNER_LEVEL, inner_values);

will be used instead. In this case the tessellation evaluation shader uses the values output from the vertex shader.

OpenGL 3.3 - How to change tesselataionlevel during run time?

1 Answers1