Codesnippet - Texture Wrapping

Code below allows you to wrap a texture using PBO. Works nice if you need to displace lets say an normal/elevation-map with fixed interval around the camera. So you can progressively insert the new areas.

void TextureOffset( uint32 resource, int dx, int dy )
{
	const int sizePerPixel = 4; const int bytesPerPixel = 1;
	const int colorFormat = GL_RGBA; int colorComponent = GL_UNSIGNED_BYTE;
	int32 w; int32 h; uint32 pbo;
	glBindTexture(GL_TEXTURE_2D, resource);
	glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &w);
	glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &h);
	dx = (w + (dx % w)) % w;
    dy = (h + (dy % h)) % h;

	//Prepase source & destination regions...
	int offetsx[] = {  dx, 0, dx, 0  }, doffetsx[] = { 0, w - dx, 0, w - dx };
	int offetsy[] = {  dy, dy, 0, 0  }, doffetsy[] = { 0, 0, h - dy, h - dy };
	int offetsw[] = {  w, dx, w, dx  }, doffetsw[] = { w - dx, w, w - dx, w };
	int offetsh[] = {  h, h, dy, dy  }, doffetsh[] = { h - dy, h - dy, h, h };
	for( int i = 0; i < 4; i++ ) offetsw[i] = offetsw[i] - offetsx[i], offetsh[i] = offetsh[i] - offetsy[i],
		doffetsw[i] = doffetsw[i] - doffetsx[i], doffetsh[i] = doffetsh[i] - doffetsy[i];

	glGenBuffersARB(1, &pbo);
	glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, pbo);
	glBufferDataARB(GL_PIXEL_UNPACK_BUFFER_ARB, w * h * sizePerPixel, 0x0, GL_DYNAMIC_COPY  );
	glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, 0x0);

	glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, pbo);
	glPixelStorei(GL_PACK_ROW_LENGTH,  w ); glPixelStorei(GL_PACK_ALIGNMENT, bytesPerPixel);
	glPixelStorei(GL_PACK_SKIP_PIXELS,  0 ), glPixelStorei(GL_PACK_SKIP_ROWS, 0);
	glGetTexImage(GL_TEXTURE_2D, 0, colorFormat, colorComponent, (void*)0);
	glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, 0);

	glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, pbo);
	glPixelStorei(GL_UNPACK_ROW_LENGTH,  w ); glPixelStorei(GL_UNPACK_ALIGNMENT,  bytesPerPixel);
	for( int i = 0, offset = 0; i < 4; i++ )
		glPixelStorei(GL_UNPACK_SKIP_PIXELS,  doffetsx[i] ), glPixelStorei(GL_UNPACK_SKIP_ROWS,  doffetsy[i]),
			glTexSubImage2D(GL_TEXTURE_2D, 0, offetsx[i], offetsy[i], offetsw[i], offetsh[i], colorFormat, colorComponent, (void*)0 );
	glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
	glDeleteBuffersARB(1, &pbo);

	glPixelStorei(GL_PACK_ROW_LENGTH,  0 ); glPixelStorei(GL_PACK_ALIGNMENT,  1);
	glPixelStorei(GL_PACK_SKIP_PIXELS,  0 ), glPixelStorei(GL_PACK_SKIP_ROWS, 0);
	glPixelStorei(GL_UNPACK_ROW_LENGTH,  0 ); glPixelStorei(GL_UNPACK_ALIGNMENT,  1);
	glPixelStorei(GL_UNPACK_SKIP_PIXELS,  0 ), glPixelStorei(GL_UNPACK_SKIP_ROWS,  0);
	glBindTexture(GL_TEXTURE_2D, 0);
}