tex2D vs. tex2Dproj

texCoord(  texX, texY, texZ , texW ) means texture coordinate after transforming from the texture matrix [ position goes through world, view, projection, and texture ].


We can use texCoord to fetch texture:
1.  float4 color = tex2D( sampler,  float2( texX / texW, texY/texW );
2.  float4 color = tex2Dporj( sampler, float4( texX, texY, texZ, texW ) );

The top-two methods will have the same result. Because tex2Dproj operator supports divide w in its interface.


http://www.gamedev.net/community/forums/topic.asp?topic_id=408894
http://bbs.gameres.com/showthread.asp?threadid=104316

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