void GenerateQuadTree(Quad parentQuad) {
this.AddChild(parentQuad);
parentQuad.PreCalculate();
if (parentQuad.LOD == this.levels) {
parentQuad.isLeaf = true;
return;
}
parentQuad.isLeaf = false;
var currX = parentQuad.transform.localPosition.x;
var currY = parentQuad.transform.localPosition.y;
var currZ = parentQuad.transform.localPosition.z;
var stride = parentQuad.size * 0.5f;
for (int i=0; i < 4; i++) {
var childQuad = new Quad(parentQuad.LOD + 1,
parentQuad.size * 0.5f,
parentQuad.size * 0.5f,
this.heightMap);
parentQuad.children.Add(childQuad);
childQuad.transform.localPosition = new Vector3(currX, currY, currZ);
this.GenerateQuadTree(childQuad);
currX = currX + stride;
if ((currX - parentQuad.transform.localPosition.x) >= parentQuad.size) {
currX = parentQuad.transform.localPosition.x;
currZ = currZ + stride;
}
}
}
// Chunked LOD implementation: http://tulrich.com/geekstuff/sig-notes.pdf
// TODO: Optimizations
// Store coordinates of bounding boxes and exclude branches in quadtree that are out of range
void ChunkedLOD(Quad quad, float scalingFactor=1.0f) {
var camPos = this.cam.transform.position;
Vector3 closestPoint = quad.boundingBox.ClosestPoint(camPos);
float distance = Vector3.Distance(closestPoint, camPos);
// Screen space error
float rho = (quad.error / distance ) * scalingFactor;
// Largest allowable screen error
float tau = 120;
if (quad.isLeaf || rho <= tau) {
quad.active = true;
} else {
// TODO: When we implement excluding of whole subbranches, we'll have to turn off visibility for all chunks in that branch
foreach (Quad q in quad.children) {
this.ChunkedLOD(q, scalingFactor);
}
}
}