// add 3 identical normal vectors to normals array using newell method
// also add line segments to normalLines
void addNormal(vec4 a, vec4 b, vec4 c) {
vec4 normal(0, 0, 0, 0);
// newell method
vec4 verts[3] = {a, b, c};
for(int i = 0; i < 3; i++) {
vec4 current = verts[i];
vec4 next = verts[(i + 1) % 3];
normal.x += (current.y - next.y)*(current.z + next.z);
normal.y += (current.z - next.z)*(current.x + next.x);
normal.z += (current.x - next.x)*(current.y + next.y);
}
normal = normalize(normal);
normals[pointIndex] = normals[pointIndex + 1] = normals[pointIndex + 2] = normal;
// add a line to normalLines by finding center of face,
// adding a line through center along normal extending out by maxSize
if(maxSize == 0) {
maxSize = box->getMaxSize();
}
vec4 center = (a + b + c) / 3;
normalLines[lineIndex] = center;
normalLines[++lineIndex] = center + (maxSize/20 * normal);
lineIndex++;
}
