So I've ran into an interesting seemingly driver-related issue. On all ATI videocards, my code works fine. But on all NVidia videocards -- the alpha component doesn't get copied when using glCopyTextImage2D. What gives?
Basically I am printing Textured text on the screen then save it as a texture which I later use (one texture per panel/window for my GUI so it doesn't get re-drawn every frame). I realize some of you may ask why save textured font into a texture, but I do it because I can use Raster font in its place as well just by calling the constructor differently, and that one works much faster when rendered to a texture then reused.
Here are a pair of screenshots to illustrate what I mean:
ATI Radeon 9800, ATI Radeon 7000:
NVidia GeForce 5700, NVidia GeForce 2 MX, NVidia GeForce 4 Ti 4200:
And here's the code of how I create a blank texture:
unsigned int iSize = (unsigned int)iWidth * iHeight * 4;
unsigned char *pTexture = new unsigned char[iSize];
ZeroMemory(pTexture, iSize);
glGenTextures(1, &iTexture);
glBindTexture(GL_TEXTURE_2D, iTexture);
glTexImage2D(GL_TEXTURE_2D, 0, 4, iWidth, iHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, pTexture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
I fill it with:
glBindTexture(GL_TEXTURE_2D, iTexture);
glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, iTWidth, iTHeight, 0);
Am I doing something wrong, or is this a driver issue?
