I've been having a lot of problems using multiple textures sent to
a glsl shader when using the framebuffer. Here is the basic problem:
I create two checkers textures that are floating point textures. I
send the textures to a glsl shader. The result (combines the
textures) is fine when not using the framebuffer. However I get
black when using the framebuffer.
I'm using OpenGL 2.0 on a Mac with OSX 10.4.10. I'm using the FBO
class from this site. I use GL_TEXTURE_2D and GL_RGBA32F_ARB (I
tried GL_RGBA16F_ARB, but it doesn't change anything). It works
fine when I download it and run it with the sample program (edge
filter on the teapot and tori). It works [i]fine[/i] with a [i]
single checkers texture[/i] as well. It's just when I try to do
multiple texturing.
The shader looks like this:
uniform sampler2D texUnit;
uniform sampler2D texUnit2;
void main(void)
{
const float offset = 1.0 / 512.0;
vec2 texCoord = gl_TexCoord[0].xy;
vec4 c = texture2D(texUnit, texCoord);
vec4 c2 = texture2D(texUnit2, texCoord);
vec4 bl = texture2D(texUnit, texCoord + vec2(-offset, -
offset));
vec4 l = texture2D(texUnit, texCoord + vec2(-offset,
0.0));
vec4 tl = texture2D(texUnit, texCoord + vec2(-offset,
offset));
vec4 t = texture2D(texUnit, texCoord + vec2( 0.0,
offset));
vec4 ur = texture2D(texUnit, texCoord + vec2( offset,
offset));
vec4 r = texture2D(texUnit, texCoord + vec2( offset,
0.0));
vec4 br = texture2D(texUnit, texCoord + vec2( offset,
offset));
vec4 b = texture2D(texUnit, texCoord + vec2( 0.0, -
offset));
gl_FragColor = c2 + (8.0 * (c + -0.125 * (bl + l + tl + t +
ur + r + br + b)));
}
The texture activation looks like:
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, _iTexture[2]);
glUniform1i(_texUnit, 0);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, _iTexture[3]);
glUniform1i(_texUnit2, 1);
Any help is greatly appreciated. I've been at this for two weeks
with no proress and its driving me crazy.
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