public MeshPrimitiveReader(MeshPrimitive srcPrim, bool doubleSided, MeshNormalsFallback fallbackNormals)
{
_Positions = srcPrim.GetVertexAccessor("POSITION")?.AsVector3Array();
_Normals = srcPrim.GetVertexAccessor("NORMAL")?.AsVector3Array();
if (_Normals == null)
{
_Normals = new XYZ[_Positions.Count];
for (int i = 0; i < _Normals.Count; ++i)
{
_Normals[i] = fallbackNormals.GetNormal(_Positions[i]);
}
}
_Color0 = srcPrim.GetVertexAccessor("COLOR_0")?.AsColorArray();
_TexCoord0 = srcPrim.GetVertexAccessor("TEXCOORD_0")?.AsVector2Array();
_Joints0 = srcPrim.GetVertexAccessor("JOINTS_0")?.AsVector4Array();
_Joints1 = srcPrim.GetVertexAccessor("JOINTS_1")?.AsVector4Array();
_Weights0 = srcPrim.GetVertexAccessor("WEIGHTS_0")?.AsVector4Array();
_Weights1 = srcPrim.GetVertexAccessor("WEIGHTS_1")?.AsVector4Array();
if (_Joints0 == null || _Weights0 == null)
{
_Joints0 = _Joints1 = _Weights0 = _Weights1 = null;
}
if (_Joints1 == null || _Weights1 == null)
{
_Joints1 = _Weights1 = null;
}
if (_Weights0 != null)
{
_Weights0 = _Weights0.ToArray(); // isolate memory to prevent overwriting source glTF.
for (int i = 0; i < _Weights0.Count; ++i)
{
var r = XYZW.Dot(_Weights0[i], XYZW.One);
_Weights0[i] /= r;
}
}
if (doubleSided) // Monogame's effect material does not support double sided materials, so we simulate it by adding reverse faces
{
var front = srcPrim.GetTriangleIndices();
var back = front.Select(item => (item.A, item.C, item.B));
_Triangles = front.Concat(back).ToArray();
}
else
{
_Triangles = srcPrim.GetTriangleIndices().ToArray();
}
}
private float SolveLeastSquares(out Vec4 start, out Vec4 end)
{
// accumulate all the quantities we need
int count = m_colours.Count;
float alpha2_sum = 0;
float beta2_sum = 0;
float alphabeta_sum = 0;
var alphax_sum = Vec4.Zero;
var betax_sum = Vec4.Zero;
for (int i = 0; i < count; ++i)
{
var alpha = m_alpha[i];
var beta = m_beta[i];
var x = m_weighted[i];
alpha2_sum += alpha * alpha;
beta2_sum += beta * beta;
alphabeta_sum += alpha * beta;
alphax_sum += alpha * x;
betax_sum += beta * x;
}
// zero where non-determinate
Vec4 a, b;
if (beta2_sum == 0)
{
a = alphax_sum / alpha2_sum;
b = Vec4.Zero;
}
else if (alpha2_sum == 0)
{
a = Vec4.Zero;
b = betax_sum / beta2_sum;
}
else
{
var factor = 1.0f / (alpha2_sum * beta2_sum - alphabeta_sum * alphabeta_sum);
a = (alphax_sum * beta2_sum - betax_sum * alphabeta_sum) * factor;
b = (betax_sum * alpha2_sum - alphax_sum * alphabeta_sum) * factor;
}
// clamp the output to [0, 1]
a = a.Clamp(Vec4.Zero, Vec4.One);
b = b.Clamp(Vec4.Zero, Vec4.One);
// clamp to the grid
a = GRID.MultiplyAdd(a, HALF).Truncate() * GRIDRCP;
b = GRID.MultiplyAdd(b, HALF).Truncate() * GRIDRCP;
// compute the error
var e1 = a * a * alpha2_sum + b * b * beta2_sum /*+ m_xxsum*/
+ 2 * (a * b * alphabeta_sum - a * alphax_sum - b * betax_sum);
// apply the metric to the error term
float error = Vec4.Dot(e1, m_metricSqr);
// save the start and end
start = a;
end = b;
return(error);
}
