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 this texCoord to fetch pixels from a texture, sampler:
1.  float4 color = tex2D( sampler,  float2( texX / texW, texY/texW );
2.  float4 color = tex2Dporj( sampler, float4( texX, texY, texZ, texW ) );

The above two methods will have the same result because tex2Dproj operator supports divide w in its interface.



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