Passing variables from a geometry shader to a fragment shader

Question

I have an GLSL geometry shader that looks like the following:

#version 150

uniform mat4 p;
uniform mat4 mv;
uniform mat3 nm;

layout(points) in;
layout(triangle_strip, max_vertices = 200) out;

out vec4 test;

void main() {
    for (int i = 0; i < gl_in.length(); i++) {
        ....        
        gl_Position = p * mv * gl_in[i].gl_Position;
        test = vec4(1.0, 0.0, 0.0, 0.0);
        EmitVertex();       
        ....        
        EndPrimitive();
    }
}

However when I try to access "test" in my fragment shader my application crashes. Here is my fragment shader:

#version 150

out vec4 fColor;
in vec4 test;

void main(void) {
    fColor = vec4(test.x, 1.0, 0.4, 0);
}

Can someone help me to pass a variable from the geometry to the fragment shader? varying is deprecated in #version 150.

What you're doing sounds ok. Where exactly is the crash occurring ? — Nicolas Lefebvre
– Nicolas Lefebvre, Commented May 16, 2011 at 20:50
Im using JOGL2, because I am writing this application in Java. If the shader looks right to you it realy helps me a lot, because then the bug might be somewhere else. I don't even get a response from the GPU, so I think this might be a bug in the Java OpenGl bindings... I currently don't know which code part I should post, because I am not sure wether it helps or not... I will update my post if I know more. Thx for the help. — iuiz
– iuiz, Commented May 17, 2011 at 18:21
Try commenting out test, and writing fColor = vec4(1.0);. If that works, test might be the problem, otherwise you can rule it out. — UncleZeiv
– UncleZeiv, Commented May 19, 2011 at 16:58

Christian Rau · Accepted Answer · 2011-05-16 20:20:40Z

2

You need to declare test as input in your fragment shader (I wonder why the shader compiles):

in vec4 test;

answered May 16, 2011 at 20:20

Christian Rau

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1 Comment

iuiz Over a year ago

Ah sorry, that was a typo, that occured while I stripped down the code for Stackoverflow :). However one upvote for you.

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