private void ProjectPolygon()
{
var norm = _normal;
bool computedNormal = false;
if (norm.X == 0.0f && norm.Y == 0.0f && norm.Z == 0.0f)
{
ComputeNormal(ref norm);
_normal = norm;
computedNormal = true;
}
int i = Vec3.LongAxis(ref norm);
_sUnit[i] = 0;
_sUnit[(i + 1) % 3] = SUnitX;
_sUnit[(i + 2) % 3] = SUnitY;
_tUnit[i] = 0;
_tUnit[(i + 1) % 3] = norm[i] > 0.0f ? -SUnitY : SUnitY;
_tUnit[(i + 2) % 3] = norm[i] > 0.0f ? SUnitX : -SUnitX;
// Project the vertices onto the sweep plane
for (var v = _mesh._vHead._next; v != _mesh._vHead; v = v._next)
{
Vec3.Dot(ref v._coords, ref _sUnit, out v._s);
Vec3.Dot(ref v._coords, ref _tUnit, out v._t);
}
if (computedNormal)
{
CheckOrientation();
}
// Compute ST bounds.
bool first = true;
for (var v = _mesh._vHead._next; v != _mesh._vHead; v = v._next)
{
if (first)
{
_bminX = _bmaxX = v._s;
_bminY = _bmaxY = v._t;
first = false;
}
else
{
if (v._s < _bminX)
{
_bminX = v._s;
}
if (v._s > _bmaxX)
{
_bmaxX = v._s;
}
if (v._t < _bminY)
{
_bminY = v._t;
}
if (v._t > _bmaxY)
{
_bmaxY = v._t;
}
}
}
}
private void ComputeNormal(ref Vec3 norm)
{
var v = _mesh._vHead._next;
var minVal = new Real[3] {
v._coords.X, v._coords.Y, v._coords.Z
};
var minVert = new MeshUtils.Vertex[3] {
v, v, v
};
var maxVal = new Real[3] {
v._coords.X, v._coords.Y, v._coords.Z
};
var maxVert = new MeshUtils.Vertex[3] {
v, v, v
};
for (; v != _mesh._vHead; v = v._next)
{
if (v._coords.X < minVal[0])
{
minVal[0] = v._coords.X; minVert[0] = v;
}
if (v._coords.Y < minVal[1])
{
minVal[1] = v._coords.Y; minVert[1] = v;
}
if (v._coords.Z < minVal[2])
{
minVal[2] = v._coords.Z; minVert[2] = v;
}
if (v._coords.X > maxVal[0])
{
maxVal[0] = v._coords.X; maxVert[0] = v;
}
if (v._coords.Y > maxVal[1])
{
maxVal[1] = v._coords.Y; maxVert[1] = v;
}
if (v._coords.Z > maxVal[2])
{
maxVal[2] = v._coords.Z; maxVert[2] = v;
}
}
// Find two vertices separated by at least 1/sqrt(3) of the maximum
// distance between any two vertices
int i = 0;
if (maxVal[1] - minVal[1] > maxVal[0] - minVal[0])
{
i = 1;
}
if (maxVal[2] - minVal[2] > maxVal[i] - minVal[i])
{
i = 2;
}
if (minVal[i] >= maxVal[i])
{
// All vertices are the same -- normal doesn't matter
norm = new Vec3 {
X = 0, Y = 0, Z = 1
};
return;
}
// Look for a third vertex which forms the triangle with maximum area
// (Length of normal == twice the triangle area)
Real maxLen2 = 0, tLen2;
var v1 = minVert[i];
var v2 = maxVert[i];
Vec3 d1, d2, tNorm;
Vec3.Sub(ref v1._coords, ref v2._coords, out d1);
for (v = _mesh._vHead._next; v != _mesh._vHead; v = v._next)
{
Vec3.Sub(ref v._coords, ref v2._coords, out d2);
tNorm.X = d1.Y * d2.Z - d1.Z * d2.Y;
tNorm.Y = d1.Z * d2.X - d1.X * d2.Z;
tNorm.Z = d1.X * d2.Y - d1.Y * d2.X;
tLen2 = tNorm.X * tNorm.X + tNorm.Y * tNorm.Y + tNorm.Z * tNorm.Z;
if (tLen2 > maxLen2)
{
maxLen2 = tLen2;
norm = tNorm;
}
}
if (maxLen2 <= 0.0f)
{
// All points lie on a single line -- any decent normal will do
norm = Vec3.Zero;
i = Vec3.LongAxis(ref d1);
norm[i] = 1;
}
}