Exhibit #2: Gouraud Shading

What we did here

• In addition to the diffuseColor uniform, we introduced a second, the lightPosition.
• We introduced a varying variable called surfaceColor.
• Lighting is computed in the vertex shader; the fragment shader just passes the interpolated color along.

Note that shading is happening in camera space. What would need to be changed to compute shading instead using a light that is at a fixed position in world space? (Hint: given the set of matrices Three.js provides, this is easy only if we know the modeling transformation is rigid.)