/// Get the inverse of this matrix as a 2-by-2.
/// Returns the zero matrix if singular.
public b2Mat33 GetInverse22(b2Mat33 M)
{
float a = ex.x, b = ey.x, c = ex.y, d = ey.y;
float det = a * d - b * c;
if (det != 0.0f)
{
det = 1.0f / det;
}
M.ex.x = det * d; M.ey.x = -det * b; M.ex.z = 0.0f;
M.ex.y = -det * c; M.ey.y = det * a; M.ey.z = 0.0f;
M.ez.x = 0.0f; M.ez.y = 0.0f; M.ez.z = 0.0f;
return (M);
}
void _setMat33Scale(ref b2Mat33 mat, float xfactor, float yfactor)
{
mat.SetZero();
mat.ex.x = xfactor;
mat.ey.y = yfactor;
mat.ez.z = 1;
}
void _setMat33Translation(ref b2Mat33 mat, cpVect t)
{
mat.SetZero();
mat.ex.x = 1;
mat.ey.y = 1;
mat.ez.x = t.x;
mat.ez.y = t.y;
mat.ez.z = 1;
}
void _setMat33Rotation(ref b2Mat33 mat, float angle)
{
mat.SetZero();
float c = cp.cpfcos(angle), s = cp.cpfsin(angle);
mat.ex.x = c; mat.ey.x = -s;
mat.ex.y = s; mat.ey.y = c;
mat.ez.z = 1;
}
b2Mat33 _b2Mul(b2Mat33 B, b2Mat33 A)
{
return new b2Mat33(b2Mul(A, B.ex), b2Mul(A, B.ey), b2Mul(A, B.ez));
}
cpVect _b2Mul(b2Mat33 A, cpVect v2)
{
b2Vec3 v = new b2Vec3(v2.x, v2.y, 1);
b2Vec3 r = v.x * A.ex + v.y * A.ey + v.z * A.ez;
return new cpVect(r.x, r.y);
}
public void updateUVs(float aspect)
{
//set up vertices
float hx = 0.5f * aspect;
float hy = 0.5f;
cpVect[] verts = new cpVect[4];
verts[0] = new cpVect(-hx, -hy);
verts[1] = new cpVect(hx, -hy);
verts[2] = new cpVect(hx, hy);
verts[3] = new cpVect(-hx, hy);
b2Mat33 r = new b2Mat33(), s = new b2Mat33();
_setMat33Rotation(ref r, Angle);
_setMat33Scale(ref s, Scale, Scale);
b2Mat33 m = _b2Mul(r, s);
for (int i = 0; i < 4; i++)
{
verts[i] = _b2Mul(m, verts[i]);
verts[i] = cpVect.cpvadd(verts[i], Center);
}
//set up uvs
cpVect[] uvs = new cpVect[4];
uvs[0] = new cpVect(0, 0);
uvs[1] = new cpVect(1, 0);
uvs[2] = new cpVect(1, 1);
uvs[3] = new cpVect(0, 1);
//set up arrays for rendering
NumPoints = 4;
NumIndices = 6;
//if (points!=null) delete[] points;
//if (uvCoords) delete[] uvCoords;
//if (indices) delete[] indices;
Points = new float[2 * NumPoints];
UvCoords = new float[2 * NumPoints];
Indices = new short[NumIndices];
for (int i = 0; i < NumPoints; i++)
{
Points[2 * i + 0] = verts[i].x;
Points[2 * i + 1] = verts[i].y;
UvCoords[2 * i + 0] = uvs[i].x;
UvCoords[2 * i + 1] = uvs[i].y;
}
Indices[0] = 0;
Indices[1] = 1;
Indices[2] = 2;
Indices[3] = 2;
Indices[4] = 3;
Indices[5] = 0;
}
/// Multiply a matrix times a vector.
public b2Vec3 b2Mul(b2Mat33 A, b2Vec3 v)
{
return v.x * A.ex + v.y * A.ey + v.z * A.ez;
}