public override double GetValue(double x, double y)
{
//Place input coordinates onto grid.
double stretchOffset = (x + y) * STRETCH_CONSTANT_2D;
double xs = x + stretchOffset;
double ys = y + stretchOffset;
//Floor to get grid coordinates of rhombus (stretched square) super-cell origin.
int xsb = fastFloor(xs);
int ysb = fastFloor(ys);
//Skew out to get actual coordinates of rhombus origin. We'll need these later.
double squishOffset = (xsb + ysb) * SQUISH_CONSTANT_2D;
double xb = xsb + squishOffset;
double yb = ysb + squishOffset;
//Compute grid coordinates relative to rhombus origin.
double xins = xs - xsb;
double yins = ys - ysb;
//Sum those together to get a value that determines which region we're in.
double inSum = xins + yins;
//Positions relative to origin point.
double dx0 = x - xb;
double dy0 = y - yb;
//We'll be defining these inside the next block and using them afterwards.
double dx_ext, dy_ext;
int xsv_ext, ysv_ext;
double value = 0;
//Contribution (1,0)
double dx1 = dx0 - 1 - SQUISH_CONSTANT_2D;
double dy1 = dy0 - 0 - SQUISH_CONSTANT_2D;
double attn1 = 2 - dx1 * dx1 - dy1 * dy1;
if (attn1 > 0) {
attn1 *= attn1;
value += attn1 * attn1 * extrapolate(xsb + 1, ysb + 0, dx1, dy1);
}
//Contribution (0,1)
double dx2 = dx0 - 0 - SQUISH_CONSTANT_2D;
double dy2 = dy0 - 1 - SQUISH_CONSTANT_2D;
double attn2 = 2 - dx2 * dx2 - dy2 * dy2;
if (attn2 > 0) {
attn2 *= attn2;
value += attn2 * attn2 * extrapolate(xsb + 0, ysb + 1, dx2, dy2);
}
if (inSum <= 1) { //We're inside the triangle (2-Simplex) at (0,0)
double zins = 1 - inSum;
if (zins > xins || zins > yins) { //(0,0) is one of the closest two triangular vertices
if (xins > yins) {
xsv_ext = xsb + 1;
ysv_ext = ysb - 1;
dx_ext = dx0 - 1;
dy_ext = dy0 + 1;
} else {
xsv_ext = xsb - 1;
ysv_ext = ysb + 1;
dx_ext = dx0 + 1;
dy_ext = dy0 - 1;
}
} else { //(1,0) and (0,1) are the closest two vertices.
xsv_ext = xsb + 1;
ysv_ext = ysb + 1;
dx_ext = dx0 - 1 - 2 * SQUISH_CONSTANT_2D;
dy_ext = dy0 - 1 - 2 * SQUISH_CONSTANT_2D;
}
} else { //We're inside the triangle (2-Simplex) at (1,1)
double zins = 2 - inSum;
if (zins < xins || zins < yins) { //(0,0) is one of the closest two triangular vertices
if (xins > yins) {
xsv_ext = xsb + 2;
ysv_ext = ysb + 0;
dx_ext = dx0 - 2 - 2 * SQUISH_CONSTANT_2D;
dy_ext = dy0 + 0 - 2 * SQUISH_CONSTANT_2D;
} else {
xsv_ext = xsb + 0;
ysv_ext = ysb + 2;
dx_ext = dx0 + 0 - 2 * SQUISH_CONSTANT_2D;
dy_ext = dy0 - 2 - 2 * SQUISH_CONSTANT_2D;
}
} else { //(1,0) and (0,1) are the closest two vertices.
dx_ext = dx0;
dy_ext = dy0;
xsv_ext = xsb;
ysv_ext = ysb;
}
xsb += 1;
ysb += 1;
dx0 = dx0 - 1 - 2 * SQUISH_CONSTANT_2D;
dy0 = dy0 - 1 - 2 * SQUISH_CONSTANT_2D;
}
//Contribution (0,0) or (1,1)
double attn0 = 2 - dx0 * dx0 - dy0 * dy0;
if (attn0 > 0) {
attn0 *= attn0;
value += attn0 * attn0 * extrapolate(xsb, ysb, dx0, dy0);
}
//Extra Vertex
double attn_ext = 2 - dx_ext * dx_ext - dy_ext * dy_ext;
if (attn_ext > 0) {
attn_ext *= attn_ext;
value += attn_ext * attn_ext * extrapolate(xsv_ext, ysv_ext, dx_ext, dy_ext);
}
return value / NORM_CONSTANT_2D;
}
