Post by cmo on Feb 6, 2021 1:48:27 GMT
I pulled the teapot OBJ files from the link in the book:
graphics.cs.utah.edu/courses/cs6620/fall2013/?prj=5
The image renders correctly geometrically, but the shading is off. After some debugging, I discovered the direction of the normal vectors is the issue. In the attached picture I've changed shadows to WHITE, to highlight the problem.
In the white part of the teapot, the normal vectors are pointing inwards, towards the center of the pot.
Has anyone else ran into this? If we use the vertex normals from the OBJ file (as for smoothing) this problem should go away.
But if we ignore the vertex normals from the file, and just populate triangles from the polygon points... Well, then the direction of the normal will depend on what order those points are entered, right? Is there a good general solution?
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