With the matrix socket being introduced into geometry nodes, we
are starting to deal with more complex transforms like perspective
projection. For those matrices projecting a point is not as simple
as just matrix multiplication, there has to be an additional normalization
step after. To solve that in an intuitive way consistent with how it's
typically solved in code, add a new "Project Point" node.
The canonical use case for now is in combination with the mouse
position, viewport transform, and raycast nodes, to find where the
mouse clicked on the edited geometry.
Pull Request: https://projects.blender.org/blender/blender/pulls/120597
3cd1c365c3