I'm trying to use luminance textures on my ATI graphics card.
The problem: I'm not being able to correctly retrieve data from my GPU. Whenever I try to read it (using glReadPixels), all it gives me is an 'all-ones' array (1.0, 1.0, 1.0...).
You can test it with this code:
#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <GL/glut.h>
static int arraySize = 64;
static int textureSize = 8;
//static GLenum textureTarget = GL_TEXTURE_2D;
//static GLenum textureFormat = GL_RGBA;
//static GLenum textureInternalFormat = GL_RGBA_FLOAT32_ATI;
static GLenum textureTarget = GL_TEXTURE_RECTANGLE_ARB;
static GLenum textureFormat = GL_LUMINANCE;
static GLenum textureInternalFormat = GL_LUMINANCE_FLOAT32_ATI;
int main(int argc, char** argv)
{
// create test data and fill arbitrarily
float* data = new float[arraySize];
float* result = new float[arraySize];
for (int i = 0; i < arraySize; i++)
{
data[i] = i + 1.0;
}
// set up glut to get valid GL context and
// get extension entry points
glutInit (&argc, argv);
glutCreateWindow("TEST1");
glewInit();
// viewport transform for 1:1 pixel=texel=data mapping
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, textureSize, 0.0, textureSize);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glViewport(0, 0, textureSize, textureSize);
// create FBO and bind it (that is, use offscreen render target)
GLuint fboId;
glGenFramebuffersEXT(1, &fboId);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fboId);
// create texture
GLuint textureId;
glGenTextures (1, &textureId);
glBindTexture(textureTarget, textureId);
// set texture parameters
glTexParameteri(textureTarget, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(textureTarget, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(textureTarget, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(textureTarget, GL_TEXTURE_WRAP_T, GL_CLAMP);
// define texture with floating point format
glTexImage2D(textureTarget, 0, textureInternalFormat, textureSize, textureSize, 0, textureFormat, GL_FLOAT, 0);
// attach texture
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, textureTarget, textureId, 0);
// transfer data to texture
//glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT);
//glRasterPos2i(0, 0);
//glDrawPixels(textureSize, textureSize, textureFormat, GL_FLOAT, data);
glBindTexture(textureTarget, textureId);
glTexSubImage2D(textureTarget, 0, 0, 0, textureSize, textureSize, textureFormat, GL_FLOAT, data);
// and read back
glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
glReadPixels(0, 0, textureSize, textureSize, textureFormat, GL_FLOAT, result);
// print out results
printf("**********************\n");
printf("Data before roundtrip:\n");
printf("**********************\n");
for (int i = 0; i < arraySize; i++)
{
printf("%f, ", data[i]);
}
printf("\n\n\n");
printf("**********************\n");
printf("Data after roundtrip:\n");
printf("**********************\n");
for (int i = 0; i < arraySize; i++)
{
printf("%f, ", result[i]);
}
printf("\n");
// clean up
delete[] data;
delete[] result;
glDeleteFramebuffersEXT (1, &fboId);
glDeleteTextures (1, &textureId);
system("pause");
return 0;
}
I also read somewhere on the internet that ATI cards don't support luminance yet. Does anyone know if this is true?