Face pointing towards the camera?

[MartinRinehart]

@adamb said:

But thats much more work than a dot product. Your turning an orientation problem into something its not.

I'm not seeing how a dot product solves the problem. Could you articulate or maybe Sketch something Up?

[thomthom]

The result of the dot product can be used to determine if its the front or back side pointing towards the camera.

t = ph.transformation_at(index) n = picked.normal.transform(t).normalize # global vector orientation c = Sketchup.active_model.active_view.camera.direction m = (c % n > 0) ? e.back_material : e.material

If the dot product is positive then the backface is facing the camera, otherwise it's the front side.

[MartinRinehart]

@thomthom said:

The result of the dot product can be used to determine if its the front or back side pointing towards the camera.

t = ph.transformation_at(index) n = picked.normal.transform(t).normalize # global vector orientation c = Sketchup.active_model.active_view.camera.direction m = (c % n > 0) ? e.back_material : e.material

If the dot product is positive then the backface is facing the camera, otherwise it's the front side.

Who is ph? Who is picked?

[thomthom]

ph is the PickHelper I used and picked is the face picked.

It was taken from my test code.

this is a more condensed sample:
back_side = camera.direction % global_face_normal > 0

[tomasz]

@thomthom said:

Any clues to how to determine that?

Check my FrontFace.
I just compare normals. The global transformation problem is solved by shooting a ray. That allows you to get an array of all parents of a face.