Calculate per-vertex smoothTangent and keep smooth normals #2068
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The
calculateSmoothTangentpreviously built the tangent space transformation matrix based upon the geometry plane only. With smooth shaded meshes, each triangle has a per-vertex normal in contrast to a per-face normal. Each normal not necessarily matches with the geometric face normal, which allows shaders to lerp between normals to create an artificial smoothness of the rendered mesh with the same amount of polygons.With this PR, the built T and B now lie within the per-vertex smooth normal and not within the geometric normal.
(The black arrow represents the geometry normal)
This is achieved by projecting the geometry points (P0, P1, P2) onto the plane of the smooth per-vertex normal plane (green) for the tangent space calculation.
The tangent space was previously also calculated per-face, not per-vertex. This hindered shaders to interpolate between tangent-spaces per-vertex (like it lerps per-vertex normals).
Also, this PR includes the retrieval of the per-vertex normals, needed for the
calculateSmoothTangentmethod and smooth shading in general.