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Re: Vertex Normals to Face Normals

To: REALbasic Games <realbasic-games at lists dot realsoftware dot com>
Subject: Re: Vertex Normals to Face Normals
From: Lo Saeteurn <realbasic at miensoftware dot com>
Date: Sun, 2 Oct 2005 17:57:37 -0700
Delivered-to: realbasic-games at lists dot realsoftware dot com
References: <05BF22B2-E499-4F81-9F25-2D04B3BC89E2 at miensoftware dot com> <126B926F-059E-45D8-8772-C72598F2BDEF at tinrocket dot com>
Hmm really?

Can you think of any way to correct face windings by facing them in the direction of the normal? In other words, I need to see if the normal is in the front or back of a triangle/face.

I guess I could just compare it against each individual vertex normal. If I do that, how do I get whether the two normals are going away from each other? I have the normal of the face in the direction of the winding and each of the vertex normals.


On Oct 2, 2005, at 5:26 PM, John Balestrieri wrote:

You can't do that. You have to compute the face normal by taking 2 vectors derived from the 3 vertices that make up each triangle and compute the vector cross product.

John


On Oct 2, 2005, at 4:03 PM, Lo Saeteurn wrote:


How do I go about getting the face normal from the three vertex normals of the same face?

Well, you probably ask why I'm doing this? To fix bad faces that have the wrong winding, but the correct normal (created by bad exporters).

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