Why does the ray fire from the cage’s edge along the average normal?

[Martin Bergwerf]

That looks right to me, naiad.

[Thomas Hock]

One thing I still don’t understand at all is (assuming the picture of Martin is accurate or very close to what happens internally):
Isn’t that basically what happens when we set the LP to be smooth (if we don’t subdivide the LP mesh a few times) ? And if so, why do we not run into the problem of flat surfaces appearing to be slightly rounded (as the angle of rays hitting the LP changes from the vert to the center of the face)? 

[Martin Bergwerf]

Hi Thomas @Nokota ,

If you use Smooth Shading, it changes the Shading Normals of the Mesh…indeed something like in my picture, but the Ray is cast like the green arrow and finds the Normal in that point to be like the blue arrow (should be straight down):

I hope that makes sense.

[Thomas Hock]

It does make sense but I still don’t really understand why a smooth shaded LP gives us a different result.
Is smooth shading changing the way Blender calculates the Normals? As in collecting the Normal Data and then interpolating those Normals to give a smoother result?

[Martin Bergwerf]

“Is smooth shading changing the way Blender calculates the Normals?”

Yes!

Have a look at the Blender 3.0 Basics Course: https://cgcookie.com/lessons/intro-to-blender-and-cg-cookie

This lesson for instance:  https://cgcookie.com/lessons/mesh-normals-and-shading 

[Thomas Hock]

Hey, sorry, I communicated unclearly.
I understand that Normals of adjacent faces get interpolated when using Smooth Shading instead of Flat shading.

While trying to explain to you better what my problem is (or rather was), I think I understood what you were trying to tell me. And I am pretty sure I now also understood the thing I could not wrap my brain around. I’m still having problems on understanding what the exact math is behind it but I’ll figure that out.

Thanks for your Help, Martin!

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