Posted by rmnoon on Aug 14, 2011; 1:45am
URL: https://forum.jogamp.org/GLJPanel-in-Lion-tp3250682p3252841.html

I seem to have narrowed it down, but I don't know how to fix it.

The issue seems to be a shader bug.  Specifically, the y component of gl_FragCoord is different (and inverted or wrong or something) on the GLJPanel vs the GLCanvas.

Here's a minimal test case:

vertex shader:
#version 120

uniform vec2 screenSize;

void main(void)
{
        gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
}

frag shader:
#version 120

uniform vec2 screenSize;

void main(void)
{
        vec4 testcolor = vec4(0.0, 0.0, 0.0, 1.0);
       
        if (gl_FragCoord.x > screenSize.x/2.0) testcolor.x += 0.5;
        if (gl_FragCoord.y > screenSize.y/2.0) testcolor.z += 0.5;

        gl_FragColor = testcolor;
}

screenSize is just a uniform that's set every draw call.

Here's what I'd expect this shader to draw (and this is what it draws with GLCanvas):



Here's what the exact same code in the GLJPanel does:



From fiddling with the second if statement I've figured out that at the top of the frame (which is 578px tall here) gl_FragCoord.y is about 450, and grows downwards (so the vertical middle is ~739).  Thus, a shader like this:

        if (gl_FragCoord.x > screenSize.x/2.0) testcolor.x += 0.5;
        if (gl_FragCoord.y > 739) testcolor.z += 0.5;

Produces this:



Any ideas on where to go next?  This happens on both software and hardware mode on both intel and amd cards.