bool operator()(const Triangle& tri) const
{
bool b = tri.CCEncompasses(m_iterVertex);
if (b)
{
HandleEdge(tri.GetVertex(0), tri.GetVertex(1));
HandleEdge(tri.GetVertex(1), tri.GetVertex(2));
HandleEdge(tri.GetVertex(2), tri.GetVertex(0));
}
return b;
}
bool operator()(const Triangle& tri) const
{
for (int i = 0; i < 3; ++i)
{
const Vertex* p = tri.GetVertex(i);
if (p >= m_pSuperTriangle && p < m_pSuperTriangle + 3)
{
return true;
}
}
return false;
}
bool TerrainBlock::PointInTriangle(Triangle& tri,Vector3& point)
{
Vector3* a = tri.GetVertex(0);
Vector3* b = tri.GetVertex(1);
Vector3* c = tri.GetVertex(2);
Vector3 v0 = (*b) - (*a);
Vector3 v1 = (*c)- (*a);
Vector3 v2 = point - (*a);
float d00 = v0.dotProduct(v0);
float d01 = v0.dotProduct(v1);
float d02 = v0.dotProduct(v2);
float d11 = v1.dotProduct(v1);
float d12 = v1.dotProduct(v2);
float invDenom = 1 / (d00 * d11 - d01 * d01);
float u = (d11 * d02 - d01*d12) * invDenom;
float v = (d00 * d12 - d01*d02) * invDenom;
return (u >=0) && (v>=0) && (u+v<1);
}
void Mesh::CalculateVertexNormals()
{
// Clear all vertex normals
for( unsigned int i = 0; i < this->_vertices.size(); ++i )
{
Vertex* vertex = this->_vertices.at(i);
if( vertex )
{
vertex->Normal() = 0.0f;
}
}
// Sum all adjacent triangle normals
for( unsigned int i = 0; i < this->_triangles.size(); ++i )
{
Triangle* triangle = this->_triangles.at(i);
if( triangle )
{
if( triangle->IsValid() )
{
for( unsigned int j = 0; j < 3; ++j )
{
Vertex* vertex = triangle->GetVertex(j);
vertex->Normal() += triangle->GetNormal();
}
}
}
}
// Normalize all vertex normals
for( unsigned int i = 0; i < this->_vertices.size(); ++i )
{
Vertex* vertex = this->_vertices.at(i);
if( vertex )
{
vertex->Normal().Normalize();
}
}
}
bool BasicPrimitiveTests::IntersectingLineAgainstTriangle(const Line & line, const Triangle & triangle, Eigen::Vector3f & rtn_point)
{
/*
Main Idea:
-> Tests if line's intersection with triangle plane is inside triangle
-> Using scalar triple products to compute signed tetrahedral volumes
-> Which are then used to compute barycentric coordinates of the line-triangle plane intersection.
Let:
-> Triangle ABC
-> Line through PQ
-> Intersection point R
-> between line and triangle's plane
To only determine intersection:
-> R must be inside triangle
-> R must be to left of AB, BC, CA if ABC is counter-clockwise vertex ordering.
-> Use scalar triple products to determine winding of AB, BC, CA compared to PQ:
-> u, v, w >= 0
-> u = [PQ PC PB]
-> v = [PQ PA PC]
-> w = [PQ PB PA]
To obtain intersection point:
-> Volumes of tetrahedra RBCP, RCAP, RABP, proportional to areas of base triangles RBC, RCA, RAB because they all have same height.
-> Barycentric points:
-> u = ( [PQ PC PB] / [PQ PC PB] + [PQ PA PC] + [PQ PB PA] )
-> v = ( [PQ PA PC] / [PQ PC PB] + [PQ PA PC] + [PQ PB PA] )
-> w = ( [PQ PB PA] / [PQ PC PB] + [PQ PA PC] + [PQ PB PA] )
*/
Eigen::Vector3f PQ = -line.GetDirection();
Eigen::Vector3f PA = triangle.GetVertex(0) - line.GetPoint();
Eigen::Vector3f PB = triangle.GetVertex(1) - line.GetPoint();
Eigen::Vector3f PC = triangle.GetVertex(2) - line.GetPoint();
Eigen::Vector3f barycentric_coords;
barycentric_coords[0] = ScalarTripleProduct(PQ, PC, PB);
if (barycentric_coords[0] < 0.0f) return false;
barycentric_coords[1] = ScalarTripleProduct(PQ, PA, PC);
if (barycentric_coords[1] < 0.0f) return false;
barycentric_coords[2] = ScalarTripleProduct(PQ, PB, PA);
if (barycentric_coords[2] < 0.0f) return false;
float sum = barycentric_coords[0] + barycentric_coords[1] + barycentric_coords[2];
if (sum < EPSILON)
{
float s, s0, s1, s2, t;
LineSegment edge_AB = LineSegment(triangle.GetVertex(0), triangle.GetVertex(1));
if (!IntersectLineAgainstSegment(line, edge_AB, s0, t)) s0 = FLT_MAX;
LineSegment edge_BC = LineSegment(triangle.GetVertex(1), triangle.GetVertex(2));
if (!IntersectLineAgainstSegment(line, edge_AB, s1, t)) s1 = FLT_MAX;
LineSegment edge_AC = LineSegment(triangle.GetVertex(0), triangle.GetVertex(2));
if (!IntersectLineAgainstSegment(line, edge_AB, s2, t)) s2 = FLT_MAX;
s = std::min(std::min(s0, s1), s2);
line.GetPointAt(s, rtn_point);
return true;
}
float denom = 1.0f / sum;
barycentric_coords *= denom;
rtn_point = triangle.GetVertex(0) * barycentric_coords[0] + triangle.GetVertex(1) * barycentric_coords[1] + triangle.GetVertex(2) * barycentric_coords[2];
return true;
}
