ive been using BGR(A) as the base internal format for my textures since the dawn of time, now checking the spec it doesnt seem to mention this as a valid base internal format (though it works), though it does mention its used for draw/readpixels, now quite why i switched over to BGR from RGB im not exactly sure, are there any benifits of using BGR, i seem to recall this is the native format for windows so there might be performance benifits, is this correct.
cheers zed
Most images are stored in BGR-format, so it is more simple to load an image and use it as a texture. For RGB you would have to swap the R and the B bytes. The BGR(A) format is a quite old extension if I'm right. It's so old that even the Microsoft OGL implementation supports it.
Marc
BGR is not an internal format, it's a format enum to tell the driver what your source image data is in, not how the driver should store it in the texture. It is the native format for win32 bitmaps, so if you're uploading win32 image data then you should use the BGR enum.
Knackered
use BGR let texture load more quickly on win32
platform.but only about load speed
It's not just Win32 machines. Any little endian system (non-Macs) will benifit from it. It has more to do with hardware than software.
It's nothing to do with the endian of the hardware.
Knackered
I think so. On windows, the decision to swap red and blue stems from some compatibility issue.Originally posted by knackered:
It's nothing to do with the endian of the hardware.
They wanted to make DIBs "device independent".
At least that's what a very old MSDN document said.
Somehow, a few images formats chose the swapped red and blue approach.
Note that a DIB memory layout is 0xXXRRGGBB, while RGBA format means 0xXXBBGGRR. Nothing to do with endianess.
Upload your textures as GL_BGRA, which tends to be faster. I think textures are commonly stored this way.
Also, some processors are switchable between little and big endian. PowerPC was one of them.
------------------------------
Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);
Does uploading from a BGR format really speed things up?
GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV is the fastest upload format on Macintosh.
On NVIDIA GPUs, yes.Originally posted by CatAtWork:
Does uploading from a BGR format really speed things up?
Posting Permissions
