I'm using texture rectangles and doing GPGPU (not that makes much difference). The shader I'm doing is so simple that I can't see why it's not working. All i want to do is to set each rgba value to a number I pass in. In this case = 2.0f.
All I do is set viewport, enable shader, pass in param, draw quad, get back data
//SET UP VIEWPORT
glEnable(iTextureType);
glViewport(0, 0, itexSizeW, itexSizeH);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, itexSizeW, 0.0, itexSizeH);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
//ENABLE SHADER
glUseProgram(m_shaders[shaderHandle].program);
//set uniforms
GLint location = fglGetUniformLocation(m_shaders[shaderHandle].program,"value");
fglUniform1f(location, 0.5f);
//DRAW A QUAD
// make quad filled to hit every pixel/texel
glPolygonMode(GL_FRONT,GL_FILL);
// and render quad
glBegin(GL_QUADS);
glTexCoord2f(0.0, 0.0);
glVertex2f(0.0, 0.0);
glTexCoord2f(itexSizeW, 0.0);
glVertex2f(itexSizeW, 0.0);
glTexCoord2f(itexSizeW, itexSizeH);
glVertex2f(itexSizeW, itexSizeH);
glTexCoord2f(0.0, itexSizeH);
glVertex2f(0.0, itexSizeH);
glEnd();
//GET DATA BACK
glBindTexture(iTextureType, mTextures[TEX_TMP2]);
float *textureData = (float*)malloc( ((int)mVoxelFaceCount*4)*sizeof(float) );
//copy frame
glCopyTexSubImage2D(iTextureType, 0, 0, 0, 0, 0, itexSizeW, itexSizeH);
glGetTexImage(iTextureType, 0, GL_RGBA, GL_FLOAT, (void*)textureData );
CHECK_OPENGL_ERR;
float data;
for (unsigned int i=0; i<mVoxelFaceCount; i++)
{
data=textureData; //everything is junk !!!
}
free(textureData);
CHECK_OPENGL_ERR;
The shade itself is just:
uniform float value;
void main (void)
{
gl_FragColor = vec4(value);
}
