I want to use Mathematica to calculate the projection of a point in 3d to a canvas in 2d. I need to convert the point (x,y,z) to where k (positive) is the distance between the viewer and the canvas. Is there any built in function that does it?

You can achieve this with `LinearFractionalTransform`: LinearFractionalTransform[ {{{1, 0, 0}, {0, 1, 0}}, {0, 0}, {0, 0, 1/k}, 1}][{x, y, z}] (* {x/(1 + z/k), y/(1 + z/k)} *) Is it worth the hassle is another question... This corresponds to the following `TransformationFunction`:

Thanks! I actually came across the various `TransformationFunction`s but this one slipped away. That's what I was looking for.

I don't know what constitutes "better" for you. I'm not sure why operating on a point as you described is a problem. If I were to do it, I'd probably define a function like this: MyProjection[k_, {x_, y_, z_}] := {x/(z/k + 1), y/(z/k + 1)} Or maybe: MyProjection[k_][{x_, y_, z_}] := {x/(z/k + 1), y/(z/k + 1)} to make currying easier.

Built-in function for projecting a point in 3D to 2D?