/// <summary>
/// Registers the mesh trianlge with the specified index with the tree.
/// </summary>
/// <returns>
/// True if the trianlge was registered and false otherwise. The only
/// scenario in which the method can return false is when the triangle
/// is degenerate.
/// </returns>
private bool RegisterTriangle(int triangleIndex)
{
// Retrieve the triangle from the mesh. If it is degenerate, we return false.
Triangle3D triangle = _octave3DMesh.GetTriangle(triangleIndex);
if (triangle.IsDegenerate)
{
return(false);
}
// Create the triangle node data and instruct the tree to add this node
var meshSphereTreeTriangle = new MeshSphereTreeTriangle(triangleIndex);
_sphereTree.AddTerminalNode(triangle.GetEncapsulatingSphere(), meshSphereTreeTriangle);
return(true);
}
/// <summary>
/// Performs a ray cast against the mesh tree and returns an instance of the 'MeshRayHit'
/// class which holds information about the ray hit. The method returns the hit which is
/// closest to the ray origin. If no triangle was hit, the method returns null.
/// </summary>
public MeshRayHit Raycast(Ray ray, TransformMatrix meshTransformMatrix)
{
// If the tree was not yet build, we need to build it because we need
// the triangle information in order to perform the raycast.
if (!_wasBuilt)
{
Build();
}
// When the sphere tree is constructed it is constructed in the mesh local space (i.e. it takes
// no position/rotation/scale into account). This is required because a mesh can be shared by
// lots of different objects each with its own transform data. This is why we need the mes matrix
// parameter. It allows us to transform the ray in the mesh local space and perform our tests there.
Ray meshLocalSpaceRay = ray.InverseTransform(meshTransformMatrix.ToMatrix4x4x);
// First collect all terminal nodes which are intersected by this ray. If no nodes
// are intersected, we will return null.
List <SphereTreeNodeRayHit <MeshSphereTreeTriangle> > nodeRayHits = _sphereTree.RaycastAll(meshLocalSpaceRay);
if (nodeRayHits.Count == 0)
{
return(null);
}
// We now have to loop thorugh all intersected nodes and find the triangle whose
// intersection point is closest to the ray origin.
float minT = float.MaxValue;
Triangle3D closestTriangle = null;
int indexOfClosestTriangle = -1;
Vector3 closestHitPoint = Vector3.zero;
foreach (var nodeRayHit in nodeRayHits)
{
// Retrieve the data associated with the node and construct the mesh triangle instance
MeshSphereTreeTriangle sphereTreeTriangle = nodeRayHit.HitNode.Data;
Triangle3D meshTriangle = _octave3DMesh.GetTriangle(sphereTreeTriangle.TriangleIndex);
// Check if the ray intersects the trianlge which resides in the node
float hitEnter;
if (meshTriangle.Raycast(meshLocalSpaceRay, out hitEnter))
{
// The trianlge is intersected by the ray, but we also have to ensure that the
// intersection point is closer than what we have found so far. If it is, we
// store all relevant information.
if (hitEnter < minT)
{
minT = hitEnter;
closestTriangle = meshTriangle;
indexOfClosestTriangle = sphereTreeTriangle.TriangleIndex;
closestHitPoint = meshLocalSpaceRay.GetPoint(hitEnter);
}
}
}
// If we found the closest triangle, we can construct the ray hit instance and return it.
// Otherwise we return null. This can happen when the ray intersects the triangle node
// spheres, but the triangles themselves.
if (closestTriangle != null)
{
// We have worked in mesh local space up until this point, but we want to return the
// hit info in world space, so we have to transform the hit data accordingly.
closestHitPoint = meshTransformMatrix.MultiplyPoint(closestHitPoint);
minT = (ray.origin - closestHitPoint).magnitude;
Vector3 worldNormal = meshTransformMatrix.MultiplyVector(closestTriangle.Normal);
return(new MeshRayHit(ray, minT, _octave3DMesh, indexOfClosestTriangle, closestHitPoint, worldNormal, meshTransformMatrix));
}
else
{
return(null);
}
}
