Calculating normals

[David Makin]

One disatwantage is when central point is on the edge of the object, then one of additional points can miss the fractal and you raytrace till hit the bounding sphere or other far part of the object.

I now just assume the DE values from the 4 adjacent points are correct and don't do any extra ray-tracing at all, this doesn't seem to cause any issues.

[Snakehand]

I have implemented my own GPU renderer from scratch, and use a "quaternion fitting" to find normals.

Here is an image rendered with flat ambient + diffuse and specular from a single point light source.



The fitting picks a random (fixed) incidental vector to the point, and searches for a rotation around this axis that brings a small perpendicular displacement flush with the boundary. The process is then repeat using the vector that has been found to be flush with the surface, and the dot product of the two flush vector gives the normal.