Thanks Christian. It's funny you mention that because since I'm not setting the
color, the quad looks like an old television tuned to a frequency not in
service, i.e. "static" or "snow". I think every time the quad is rendered each
fragment's color is set to whatever value is in some uninitialized portion of
memory, and each fragment changes color each time it is rendered. Quite a funny
effect!
I added the following line to set the color, and now it is always blue, but
it's still not putting a hole in my quad, it's all there or all gone depending
on whether I say if (fDist < rad) or if (fDist > rad):
Code:
// The fragment shader program source code
std::string szFragSource(
"uniform vec3 center;\n"
"uniform float rad;\n"
"void main()\n"
"{\n"
"float fDistX = gl_FragCoord.x - center.x;\n"
"float fDistY = gl_FragCoord.y - center.y;\n"
"float fDistZ = gl_FragCoord.z - center.z;\n"
"float fDist = sqrt(fDistX * fDistX + fDistY * fDistY + fDistZ * fDistZ);\n"
"gl_FragColor = vec4(0.0,0.0,1.0,1.0);\n"
"if (fDist < rad) discard;\n"
"}\n"
);
Any other ideas about why my code doesn't achieve what I want? For example, am
I using gl_FragCoord correctly? Are there other errors in my frag source?
Thanks again!
cbuchner1 wrote:
> I believe your fragment shader is not setting the output fragment color at
> all, which is a minimum requirement for a fragment shader to work.
>
>
> Christian
>
>
>
> 2015-07-23 23:59 GMT+02:00 Erik Hensens < ()>:
>
> > Sorry for the triplicate post, I received an error message on trying to
> > post until I removed the quotes...
> >
> > ------------------
> > Read this topic online here:
> > http://forum.openscenegraph.org/viewtopic.php?p=64458#64458
> > (http://forum.openscenegraph.org/viewtopic.php?p=64458#64458)
> >
> >
> >
> >
> >
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