DrawSetTextureRGBA

void DrawSetTextureRGBA(int id, const unsigned char *rgba, int wide, int tall, int hardwareFilter, bool forceReload)

This is a function that you should use to draw raw RGBA data to the HUD, for example when you are rendering a mask. DrawSetTextureRGBA is one of the worst documented features in the SDK, and hasn't been seen working in any way, as far as I know. The following code is by the book, but doesn't work at all (it just paints a white fog over the screen).

	//abPic is an unsigned int[128][128] with some texture data
	m_iHudTexture=surface()->CreateNewTextureID();
	surface()->DrawSetTextureRGBA(m_iHudTexture,(unsigned char*)abPic,128,128,false,true);
	Assert(surface()->IsTextureIDValid(m_iHudTexture));
	surface()->DrawSetColor(Color(255,255,255,128));
	surface()->DrawTexturedRect(0,0,GetWide(),GetTall());

Emails on HLCoders (March 2005, [hlcoders] DrawSetTextureRGBA) about this issue haven't helped a bit. We, as the Source modding community can only hope Valve will eventually fix this, or give information on how this function should be used.