private Dictionary <int, int> indexLookup;//= new Dictionary<int, int>();
private void BuildMeshForObject()
{
List <int> triangles = new List <int>();
// Use a BSP tree to find nearby triangles at log(n) speeds.
tree.FindClosestTriangles(position, scale, triangles);
// Calculate the matrix needed to transform a point from the obj's local mesh, to our local mesh.
// Matrix4x4 mat = transform.worldToLocalMatrix * obj.transform.localToWorldMatrix;
// Clear the index lookup, we use it to check which verticies are shared.
// This keeps us from having to rebuild the mesh so intricately.
indexLookup = new Dictionary <int, int>(triangles.Count);
// TODO: split this up into more jobs.
for (int i = 0; i < triangles.Count; i++)
{
// We use the indices of the original mesh's triangles to determine which
// verticies are shared. So we don't have to calculate that ourselves.
// we grab them here.
int i1, i2, i3;
tree.GetIndices(triangles [i], out i1, out i2, out i3);
// Here we get the points of the obj's mesh in our local space.
Vector3 v1, v2, v3;
tree.GetVertices(triangles [i], out v1, out v2, out v3);
v1 = mat.MultiplyPoint(v1);
v2 = mat.MultiplyPoint(v2);
v3 = mat.MultiplyPoint(v3);
Vector3 n1, n2, n3;
tree.GetNormals(triangles [i], out n1, out n2, out n3);
// We do a quick normal calculation to see if the triangle is mostly facing us.
// we have to recalculate it since the normal is different in our local space
// (maybe we could just transform the original bsptree's precomputed normals with the matrix ?)
Vector3 side1 = v2 - v1;
Vector3 side2 = v3 - v1;
Vector3 normal = Vector3.Cross(side1, side2).normalized;
if (normal.y <= 0.2f)
{
continue;
}
// To prevent z-fighting, I randomly offset each vertex by the normal.
v1 += normal * offset;
v2 += normal * offset;
v3 += normal * offset;
// First we check to see if a vertex has already been grabbed and calculated.
// If it has been, we just use that as the index for the triangle.
// Otherwise we create a new vertex, with coorisponding UV mapping.
// Since we're in a local space where the decal spans from -0.5f to 0.5f,
// Our UV is just the x and z values in the space offset by 0.5f
int ni1, ni2, ni3;
if (!indexLookup.TryGetValue(i1, out ni1))
{
verts.Add(v1);
uvs.Add(new Vector2(v1.x + 0.5f, v1.z + 0.5f));
normals.Add(rotation * n1);
ni1 = verts.Count - 1;
indexLookup [i1] = ni1;
}
if (!indexLookup.TryGetValue(i2, out ni2))
{
verts.Add(v2);
uvs.Add(new Vector2(v2.x + 0.5f, v2.z + 0.5f));
normals.Add(rotation * n2);
ni2 = verts.Count - 1;
indexLookup [i2] = ni2;
}
if (!indexLookup.TryGetValue(i3, out ni3))
{
verts.Add(v3);
uvs.Add(new Vector2(v3.x + 0.5f, v3.z + 0.5f));
normals.Add(rotation * n3);
ni3 = verts.Count - 1;
indexLookup [i3] = ni3;
}
// Finally we add the triangle to the triangle list.
tri.AddLast(ni1);
tri.AddLast(ni2);
tri.AddLast(ni3);
}
}