public IEnumerable <HitInfo <V> > Raycast(RayDescription ray)
{
if (mesh.Topology != Topology.Triangles)
{
yield break;
}
Ray3D r = new Ray3D(ray.Origin, ray.Direction + 0.000000001f); // epsilon deviation of the direction to avoid indefinitions
float minT, maxT;
if (!box.Intersect(r, out minT, out maxT))
{
yield break;
}
maxT = min(maxT, ray.MaxT);
float t = max(ray.MinT, minT);
float3 P = r.X + r.D * t;
int3 cell = (int3)min(((P - box.Minimum) * resolution / (box.Maximum - box.Minimum)), resolution - 1);
float3 side = r.D > 0;
int3 cellInc = (r.D > 0) * 2 - 1;
float3 corner = box.Minimum + (cell + side) * (box.Maximum - box.Minimum) / resolution;
float3 alphas = (corner - r.X) / r.D;
float3 alphaInc = (box.Maximum - box.Minimum) / abs(resolution * r.D);
while (t < maxT)
{
float nextT = min(alphas.x, min(alphas.y, alphas.z));
if (any(cell < 0) || any(cell >= resolution))
{
yield break; // just for numerical problems, traversal could go outside grid.
}
// check current cell
if (triangleHash[cell.z, cell.y, cell.x] != null)
{
List <HitInfo <V> > hits = new List <HitInfo <V> >();
foreach (var i in triangleHash[cell.z, cell.y, cell.x])
{
V v1 = mesh.Vertices[mesh.Indices[i * 3 + 0]];
V v2 = mesh.Vertices[mesh.Indices[i * 3 + 1]];
V v3 = mesh.Vertices[mesh.Indices[i * 3 + 2]];
Triangle3D tri = new Triangle3D(v1.Position, v2.Position, v3.Position);
float triT;
float3 baricenter;
if (tri.Intersect(r, out triT, out baricenter))
{
if (triT >= t && triT <= nextT)
{
hits.Add(new HitInfo <V>
{
T = triT,
Attribute = v1.Mul(baricenter.x).Add(v2.Mul(baricenter.y)).Add(v3.Mul(baricenter.z))
});
}
}
}
hits.Sort((h1, h2) => h1.T.CompareTo(h2.T)); // only need to sort hits inside a cell, because cells are iterated in ray-order
foreach (var hi in hits)
{
yield return(hi);
}
}
// advance ray to next cell
int3 movement = new int3(alphas.x <= alphas.y && alphas.x <= alphas.z, alphas.y < alphas.x && alphas.y <= alphas.z, alphas.z < alphas.x && alphas.z < alphas.y);
cell += movement * cellInc;
alphas += movement * alphaInc;
t = nextT;
}
}
