tex2Dproj equivalent in Metal iOS

Question

How do you do hardware accelerated texture projection in Metal? I cannot find any reference or resource that describes how to do it.

Answer 1

You just do the divide yourself.

OpenGL:

a = tex2Dproj( texture, texcoord.xyzw )
b = tex2Dproj( texture, texcoord.xyz )

Metal equivilent:

a = texture.sample( sampler, texcoord.xy/texcoord.w )
b = texture.sample( sampler, texcoord.xy/texcoord.z )

(Choose 'a' or 'b' depending on the type of projection you are doing, more commonly it is 'a')