Face pointing towards the camera?

MartinRinehart

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.