Contents
How do you calculate surface normals?
A surface normal for a triangle can be calculated by taking the vector cross product of two edges of that triangle. The order of the vertices used in the calculation will affect the direction of the normal (in or out of the face w.r.t. winding).
What is a normal of a triangle?
The normal of the triangle, or vector C is the cross product of A and B. The result is also equal to (0,0,1) as with the right-hand coordinate system example (the vertices coordinates are the same, therefore the vectors A and B are the same as well as the result of the cross product AxB).
How to find the surface normal of a triangle?
If I have a triangle with 3 points P 1, P 2, and P 3, each with x, y, and z coordinates, how do I find the surface normal N in x, y, and z such that I’m looking for a simple formula that uses values like x 1, x 2, or y 3, and doesn’t involve complicated equations or cross products.
What’s the best way to compute vertex normals?
Different techniques for computing vertex normals when there is not smooth surface to compute them from exist, but we won’t study them in this lesson. For now, use a software such as Maya or Blender to do this job for you (in Maya you can select your polygon mesh and select the option Soften Edge in the Normals menu).
How are normals and vertex normals used in shading?
A Simple Shading Effect: Facing Ratio. Now that we know how to compute the normal of a point on the surface of an object, we have enough information already to create a simple shading effect called facing ratio. This technique consists of computing the dot product of the normal of the point that we want to shade and the viewing direction.
How to compute the color of a point on the surface?
When we want to compute the color of a point on the surface a triangle, rather than using the face normal, we can compute a “fake smooth” normal by linearly interpolating the vertex normals defined at the triangle’s vertices using the hit point barycentric coordinates.