Some questions about the geometry shader

[laurent7601]

Hi! I’m trying to compile a shader with a geometry shader but I have some problems.

-The first question is which primitive to set to my geometry shader input if I draw quads ?
-And the second question is how to pass outtput variables from my vertex shader to input variables of my fragment shader ?

I have this link error when compiling the geometry shader :

error: “fTexCoords” not declared as an output from the previous stage
The previous stage of the fragment shader is the geometry shader I guess and not the vertex shader this is probably why I’ve this error.

[GClements]

@laurent7601

-The first question is which primitive to set to my geometry shader input if I draw quads ?

Triangles. Quads aren’t supported in the core profile; in the compatibility profile they’re decomposed into triangles.

@laurent7601

-And the second question is how to pass outtput variables from my vertex shader to input variables of my fragment shader ?

You have to match them with geometry shader inputs and have the geometry shader copy them to its outputs, which must be matched with fragment shader inputs. There is no way to have them automatically “pass-through” the geometry shader.

If you aren’t using interface blocks, you need to use different names for the geometry shader inputs and outputs.