raytracer.hlsl

	// flip coordinate space such that ray is always positive (simplifies stepping logic)
	// keep track of flip via flipmask
	bool3 ray_neg = dir < 0.0;
	float3 flipped = ray_neg ? -pos : pos;

	int3 flipmask = ray_neg ? -1 : 0;

	float3 absDir = abs(dir);

	float dist = 0.0;

	int skipLOD = 0;

	// get initial coordinate based on flipped coordinate
	int3 mapPos = floor(flipped);
	mapPos &= 0xffffffff << skipLOD;

	for (;;) {
		int3 unflipped = (mapPos ^ flipmask) >> skipLOD; // unflipped mapPos shifted down for texture indexing
		
		// read octree cell at unflipped coord with current skipLOD
		int voxel = texelFetch(octree, unflipped, skipLOD).r;
		
		if (voxel != AIR) {
			// non-air octree cell
			if (skipLOD == 0)
				break; // found solid leaf voxel
			
			// decend octree
			skipLOD--;
			int3 mid_planes = mapPos + (1 << skipLOD);
			
			// upate coord by determining which child octant is entered first
			// by comparing ray hit against middle plane hits
			float3 tmidv = ((float3)mid_planes - flipped) / absDir;
			
			mapPos = tmidv < hitDistance.xxx ? mid_planes : mapPos;
			
			// have decended one level of the octree, instead of stepping
			// go back repeat outer loop until fully air cell is found or non-air leaf voxel is found
			
		} else {
			float3 exit_planes = mapPos + rayMoveIterations;
			float3 exit_distances = (exit_planes - flipped) / absDir;

			hitDistance = min(min(exit_distances.x, exit_distances.y), exit_distances.z);
			
			// step on axis where exit distance is lowest
			int stepcoord;
			if (t0v.x == dist) {
				mapPos.x = exit_planes.x;
				stepcoord = mapPos.x;
			} else if (t0v.y == dist) {
				mapPos.y = exit_planes.y;
				stepcoord = mapPos.y;
			} else {
				mapPos.z = exit_planes.z;
				stepcoord = mapPos.z;
			}
			
			// step up to highest changed octree parent cell
			mip = firstbitlow(stepcoord);
			
			// round down mapPos to lower corner of (potential) parent cell
			mapPos &= ROUNDMASK << mip;
			
			rayDistance--;
			//// exit when either stepped out of world or max ray dist reached
			insideBounds = rayDistance > 0 &&
				mapPos.x < (dir.x < 0 ? 0 : _WorldBounds.x) &&
				mapPos.y < (dir.y < 0 ? 0 : _WorldBounds.y) &&
				mapPos.z < (dir.z < 0 ? 0 : _WorldBounds.z);
		}
	}

	// handle hit