Investigate non-normalized normals

[arose]

Investigate non-normalized normals observed by @sukolsak in #174.

[arose]

Hey @sukolsak, not sure if I remember correctly: was there another source of non-normalized normals?

[sukolsak]

@arose There are two sources that I have found so far:

• Normals in arrowheads. See #179
• The add*Cylinder methods. These methods call MeshBuilder.addPrimitive(state, tmpCylinderMat, cylinder), which does this

const n = mat3directionTransform(tmpMat3, t);
...
// normal
v3transformMat3(tmpV, v3fromArray(tmpV, na, i), n);

tmpV is not normalized because of the non-uniform scaling of cylinders.