Fault with Compressed PBO texture loader

#1

I am working with compressed textures, which i have loaded successfully using the pixel pointer with glCompressedTexImage2DARB, but unfortunately when I use the PBO texture upload, it comes up wrong :frowning: .

Now I am working with PBOā€™s. I have tried with this code

snip example code


void CreateTexture(Image* imagedata)
{
	switch(imagedata->v_pixelformat)
	{
	case COMPRESSED_DXT1:
		gl_internalformat=GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
		gl_format=GL_RGBA;
		break;
	case COMPRESSED_DXT3:
		gl_internalformat=GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
		gl_format=GL_RGBA;
		break;
	case COMPRESSED_DXT5:
		gl_internalformat=GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
		gl_format=GL_RGBA;
		break;
	}
		
	glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, 0);

	glGenBuffersARB(1,&pBuf_GL);
	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
	glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, pBuf_GL);
	glBufferDataARB(GL_PIXEL_UNPACK_BUFFER_ARB, imagedata->imageSize, NULL, GL_STATIC_DRAW_ARB);

	glGenTextures(1,&ID);
	glBindTexture(GL_TEXTURE_2D, ID);

	iOffset		= 0;

	int iWidth = imagedata->GetWidth();
	int iHeight = imagedata->GetHeight();
	unsigned int iNumMipMaps = imagedata->num_mipmaps;
	
	blockSize=(imagedata->v_pixelformat == V_COMPRESSED_DXT1) ? 8 : 16;

	if(iNumMipMaps < 2)
	{
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	}
	else
	{
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	}

	for(Vuint i=0; i<iNumMipMaps; i++)
	{
	iSize = ((iWidth + 3) / 4) * ((iHeight + 3) / 4) * blockSize;
	glCompressedTexImage2DARB(GL_TEXTURE_2D, i, gl_internalformat, iWidth, iHeight, 0, iSize, NULL);
	iOffset += iSize;

	iWidth /= 2;
	iHeight /= 2;
	}

	unsigned char* tembuffer = glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, GL_WRITE_ONLY_ARB);
	memcpy(tempbuffer,imagedata->pixels,
	glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB);
}

void BindTexture(Image* imagedata)
{
	glBindTexture (GL_TEXTURE_2D, ID);
	glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, pBuf_GL);

	int iOffset=0;
	int iWidth = imagedata->GetWidth();
	int iHeight = imagedata->GetHeight();
	int iSize;

	for(Vuint i = 0; i < texture->v_num_mipmaps; i++)
	{
		iSize = ((iWidth + 3) / 4) * ((iHeight + 3) / 4) * blockSize;
		glCompressedTexSubImage2DARB(GL_TEXTURE_2D,i,0,0, iWidth, iHeight,gl_format, iSize,BUFFER_OFFSET(iOffset));

	iOffset += iSize;
	iHeight /= 2;
	iHeight /= 2;
	}
}

When I placeā€¦
glCompressedTexImage2DARB(GL_TEXTURE_2D, i, gl_internalformat, iWidth, iHeight, 0, iSize, pixels);
The texture comes out right, but if I PBO the texture (by leaving the pixel data pointer NULL) it comes with a bitmap dump.

I was wondering if it is how I have used the glCompressedTexSubImage function which most likely be faulty. Does anybody know where the fault is in this codeā€¦

Thank you

#2

IIRC, the spec doesnā€™t allow for (and some vendorsā€™ implementation crashes/misbehaves when) passing a NULL pointer to glCompressedTexImage2D, but you can get what you want by calling glTexImage2D with the right internal format and no buffer bound and a NULL pointer to force-allocate the MIPmaps, then call glCompressedTexSubImage2D to slap the compressed texel data in there. This NULL pointer is hopefully not a problem when a PBO is bound, but I mentioned this just in case. If none of the below fixes it, investigate this last.

Also, youā€™ve got that NULL (i.e. PBO offset 0) in a for loop to load all MIPmaps, no? So youā€™re going to try to load all the MIPmap level texels from the DXT blocks at the front of the base map (level 0) only. Probably want BUFFER_OFFSET(iOffset) instead.

And the Map/memcpy/Unmap thing at the end puzzles me. Donā€™t know what youā€™re trying to accomplish there, but in the interests of pipelining, might want to stick a glBufferData( GL_PIXEL_UNPACK_BUFFER_ARB, pbo_size, 0, GL_STREAM_DRAW ); before it so GL can use another buffer.

Also, in your glCompressedTexSubImage2D call, your ā€œformatā€ parameter needs to be the actual format of the data. Youā€™re providing GL_RGBA (ambiguous and incorrect if your data is already DXT compressed), when you probably mean it to be GL_COMPRESSED_RGBA_S3TC_DXT?.

Also, your Map memcpy got chopped, but Iā€™m not convinced youā€™re not trashing your PBO contents right there.

Also, in your last subload loop, youā€™re dividing iHeight by 2 twice, but not adjusting iWidth.

And try sticking some glGetError() checks in there ā€“ you might find something.