Lecture 6: Graphics Pipeline (37)
wcyjames

Not sure if the lecture covered this slide... What does the problem: length of vectors ask? Does it mean we need to normalize the vertex normals for calculation?

kbiesiadecki141

Similar to the question above, I don't understand how we interpolate vertex normals. What value are we interpolating (e.g. with colors, you can weight each color with a/b/g). Part of my confusion also lies in the image; what is the circle and why are there tangents drawn to it?

ziyaointl

@wcyjames Because shaders usually expect normal vectors to be of norm 1, so you are right that the normal vectors are usually normalized after baryzentric interpolation. A good question to think about is what abnormalities will result if Blinn-Phong shading is applied on normal vectors that are not normalized.

ziyaointl

@kbiesiadecki141 The interpolation of normals is analogous to the interpolation of colors - both are done element-wise. As for elements on the slide, the circle is the idealized geometry that we want to represent, and the tangents represent triangle meshes that approximate the underlying geometry.

j316chuck

Got it, so we linearly interpolate the 2 vectors at the vertexes to get a vector at a pixel?

ziyicui2022

Why we need to normalized ? What will happen if we don't normalize the normal vector

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