Normals

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Obunako 101 Jul 19, 2003 at 17:42

I always work with one normal associate with a polygon, but 3ds format export one normals for each vertex :blink: I don’t understand, some one help me ?

Thanks.

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dk 158 Jul 19, 2003 at 19:08

Yes, it’s possible to have a normal for each vertex. This is done for lighting calculations. If you find the normal to a triangle, you are finding a “Face Normal”. If you give OpenGL a face normal for lighting, it will make your object look really flat and not very round. If we find the normal for each vertex, it makes the smooth lighting look. This also covers up blocky looking objects and they appear to have more polygons than they do.

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moomin 101 Jul 21, 2003 at 08:23

per vertex normals are teh w1n!!!!

Render a sphere with per face normals, then

Render a sphere with per vertex normals

the difference is amazing.

That reminds me how many of the neighbour face value normals should I use to calculate the per vertex value?

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anubis 101 Jul 21, 2003 at 08:23

imagine it like this :

you find per-polygon normals for each polygon in your model. obviously this will result in surfaces that will look very flat when lit as apex said. the easiest way around this is to average the normals of faces that share a vertex. you then assign this new averaged normal to the shared vertex and thus get a different normal for each vertex instead of one for each face.

result == smoother shading.

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davepermen 101 Jul 30, 2003 at 08:47
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donBerto 101 Jul 31, 2003 at 21:03

davepermen: a VERY nice example.

:yes:

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davepermen 101 Aug 03, 2003 at 20:20

thanks