public float DistanceTo(STVertex vertex)
{
float deltaX = vertex.Position.X - Position.X;
float deltaY = vertex.Position.Y - Position.Y;
float deltaZ = vertex.Position.Z - Position.Z;
return((float)Math.Sqrt(deltaX * deltaX + deltaY * deltaY + deltaZ * deltaZ));
}
private void ApplyTanBitanArray(Vector3[] tanArray, Vector3[] bitanArray)
{
if (Vertices.Count < 3)
{
return;
}
for (int i = 0; i < Vertices.Count; i++)
{
STVertex v = Vertices[i];
Vector3 newTan = tanArray[i];
Vector3 newBitan = bitanArray[i];
// The tangent and bitangent should be orthogonal to the normal.
// Bitangents are not calculated with a cross product to prevent flipped shading with mirrored normal maps.
v.Tangent = new Vector4(Vector3.Normalize(newTan - v.Normal * Vector3.Dot(v.Normal, newTan)), 1);
v.Bitangent = new Vector4(Vector3.Normalize(newBitan - v.Normal * Vector3.Dot(v.Normal, newBitan)), 1);
v.Bitangent *= -1;
}
}
private void CalculateTanBitanArrays(List <uint> faces, Vector3[] tanArray, Vector3[] bitanArray, int uvSet = 0)
{
if (Vertices.Count < 3 || faces.Count <= 0)
{
return;
}
for (int i = 0; i < faces.Count; i += 3)
{
STVertex v1 = Vertices[(int)faces[i]];
STVertex v2 = Vertices[(int)faces[i + 1]];
STVertex v3 = Vertices[(int)faces[i + 2]];
float x1 = v2.Position.X - v1.Position.X;
float x2 = v3.Position.X - v1.Position.X;
float y1 = v2.Position.Y - v1.Position.Y;
float y2 = v3.Position.Y - v1.Position.Y;
float z1 = v2.Position.Z - v1.Position.Z;
float z2 = v3.Position.Z - v1.Position.Z;
float s1, s2, t1, t2;
s1 = v2.TexCoords[uvSet].X - v1.TexCoords[uvSet].X;
s2 = v3.TexCoords[uvSet].X - v1.TexCoords[uvSet].X;
t1 = v2.TexCoords[uvSet].Y - v1.TexCoords[uvSet].Y;
t2 = v3.TexCoords[uvSet].Y - v1.TexCoords[uvSet].Y;
float div = (s1 * t2 - s2 * t1);
float r = 1.0f / div;
// Fix +/- infinity from division by 0.
if (r == float.PositiveInfinity || r == float.NegativeInfinity)
{
r = 1.0f;
}
float sX = t2 * x1 - t1 * x2;
float sY = t2 * y1 - t1 * y2;
float sZ = t2 * z1 - t1 * z2;
Vector3 s = new Vector3(sX, sY, sZ) * r;
float tX = s1 * x2 - s2 * x1;
float tY = s1 * y2 - s2 * y1;
float tZ = s1 * z2 - s2 * z1;
Vector3 t = new Vector3(tX, tY, tZ) * r;
// Prevents black tangents or bitangents due to having vertices with the same UV coordinates.
float delta = 0.00075f;
bool sameU, sameV;
sameU = (Math.Abs(v1.TexCoords[uvSet].X - v2.TexCoords[uvSet].X) < delta) &&
(Math.Abs(v2.TexCoords[uvSet].X - v3.TexCoords[uvSet].X) < delta);
sameV = (Math.Abs(v1.TexCoords[uvSet].Y - v2.TexCoords[uvSet].Y) < delta) &&
(Math.Abs(v2.TexCoords[uvSet].Y - v3.TexCoords[uvSet].Y) < delta);
if (sameU || sameV)
{
// Let's pick some arbitrary tangent vectors.
s = new Vector3(1, 0, 0);
t = new Vector3(0, 1, 0);
}
// Average tangents and bitangents.
tanArray[faces[i]] += s;
tanArray[faces[i + 1]] += s;
tanArray[faces[i + 2]] += s;
bitanArray[faces[i]] += t;
bitanArray[faces[i + 1]] += t;
bitanArray[faces[i + 2]] += t;
}
}
