Optimized NoiseFunctionSimplex by inlining

This causes duplicated code, but it should be removed when
NoiseGenerator is not used anymore

src/basics/NoiseFunctionSimplex.cpp

@@ -141,6 +141,7 @@ double noiseSimplexGet1DValue(double x) {
 }
 
 double noiseSimplexGet2DValue(double x, double y) {
+    // FIXME duplicated
     double n0, n1, n2; /* Noise contributions from the three corners */
     /* Skew the input space to determine which simplex cell we're in */
     double s = (x + y) * _F2; /* Hairy factor for 2D */
@@ -203,6 +204,7 @@ double noiseSimplexGet2DValue(double x, double y) {
 }
 
 double noiseSimplexGet3DValue(double x, double y, double z) {
+    // FIXME duplicated
     double n0, n1, n2, n3; /* Noise contributions from the four corners */
     /* Skew the input space to determine which simplex cell we're in */
     double s = (x + y + z) * _F3; /* Very nice and simple skew factor for 3D */
@@ -469,11 +471,189 @@ double noiseSimplexGet4DValue(double x, double y, double z, double w) {
 }
 
 double NoiseFunctionSimplex::getBase2d(double x, double y) const {
-    return noiseSimplexGet2DValue(x, y) - 0.5;
+    double n0, n1, n2; /* Noise contributions from the three corners */
+    /* Skew the input space to determine which simplex cell we're in */
+    double s = (x + y) * _F2; /* Hairy factor for 2D */
+    int i = _fastfloor(x + s);
+    int j = _fastfloor(y + s);
+    double t = (i + j) * _G2;
+    double X0 = i - t; /* Unskew the cell origin back to (x,y) space */
+    double Y0 = j - t;
+    double x0 = x - X0; /* The x,y distances from the cell origin */
+    double y0 = y - Y0;
+    /* For the 2D case, the simplex shape is an equilateral triangle.
+       Determine which simplex we are in. */
+    int i1, j1; /* Offsets for second (middle) corner of simplex in (i,j) coords */
+    if (x0 > y0) {
+        i1 = 1;
+        j1 = 0;
+    } /* lower triangle, XY order: (0,0)->(1,0)->(1,1) */
+    else {
+        i1 = 0;
+        j1 = 1;
+    }                          /* upper triangle, YX order: (0,0)->(0,1)->(1,1) */
+                               /* A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
+                                  a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
+                                  c = (3-sqrt(3))/6 */
+    double x1 = x0 - i1 + _G2; /* Offsets for middle corner in (x,y) unskewed coords */
+    double y1 = y0 - j1 + _G2;
+    double x2 = x0 - 1.0 + 2.0 * _G2; /* Offsets for last corner in (x,y) unskewed coords */
+    double y2 = y0 - 1.0 + 2.0 * _G2;
+    /* Work out the hashed gradient indices of the three simplex corners */
+    int ii = i & 255;
+    int jj = j & 255;
+    int gi0 = _permutationsMod12[ii + _permutations2[jj]];
+    int gi1 = _permutationsMod12[ii + i1 + _permutations2[jj + j1]];
+    int gi2 = _permutationsMod12[ii + 1 + _permutations2[jj + 1]];
+    /* Calculate the contribution from the three corners */
+    double t0 = 0.5 - x0 * x0 - y0 * y0;
+    if (t0 < 0)
+        n0 = 0.0;
+    else {
+        t0 *= t0;
+        n0 = t0 * t0 * _dot2(_grad3[gi0], x0, y0); /* (x,y) of _grad3 used for 2D gradient */
+    }
+    double t1 = 0.5 - x1 * x1 - y1 * y1;
+    if (t1 < 0)
+        n1 = 0.0;
+    else {
+        t1 *= t1;
+        n1 = t1 * t1 * _dot2(_grad3[gi1], x1, y1);
+    }
+    double t2 = 0.5 - x2 * x2 - y2 * y2;
+    if (t2 < 0)
+        n2 = 0.0;
+    else {
+        t2 *= t2;
+        n2 = t2 * t2 * _dot2(_grad3[gi2], x2, y2);
+    }
+    /* Add contributions from each corner to get the final noise value.
+       The result is scaled to return values in the interval [-0.5,0.5]. */
+    return 35.0 * (n0 + n1 + n2);
 }
 
 double NoiseFunctionSimplex::getBase3d(double x, double y, double z) const {
-    return noiseSimplexGet3DValue(x, y, z) - 0.5;
+    double n0, n1, n2, n3; /* Noise contributions from the four corners */
+    /* Skew the input space to determine which simplex cell we're in */
+    double s = (x + y + z) * _F3; /* Very nice and simple skew factor for 3D */
+    int i = _fastfloor(x + s);
+    int j = _fastfloor(y + s);
+    int k = _fastfloor(z + s);
+    double t = (i + j + k) * _G3;
+    double X0 = i - t; /* Unskew the cell origin back to (x,y,z) space */
+    double Y0 = j - t;
+    double Z0 = k - t;
+    double x0 = x - X0; /* The x,y,z distances from the cell origin */
+    double y0 = y - Y0;
+    double z0 = z - Z0;
+    /* For the 3D case, the simplex shape is a slightly irregular tetrahedron.
+       Determine which simplex we are in. */
+    int i1, j1, k1; /* Offsets for second corner of simplex in (i,j,k) coords */
+    int i2, j2, k2; /* Offsets for third corner of simplex in (i,j,k) coords */
+    if (x0 >= y0) {
+        if (y0 >= z0) {
+            i1 = 1;
+            j1 = 0;
+            k1 = 0;
+            i2 = 1;
+            j2 = 1;
+            k2 = 0;
+        } /* X Y Z order */
+        else if (x0 >= z0) {
+            i1 = 1;
+            j1 = 0;
+            k1 = 0;
+            i2 = 1;
+            j2 = 0;
+            k2 = 1;
+        } /* X Z Y order */
+        else {
+            i1 = 0;
+            j1 = 0;
+            k1 = 1;
+            i2 = 1;
+            j2 = 0;
+            k2 = 1;
+        }    /* Z X Y order */
+    } else { /* x0<y0 */
+        if (y0 < z0) {
+            i1 = 0;
+            j1 = 0;
+            k1 = 1;
+            i2 = 0;
+            j2 = 1;
+            k2 = 1;
+        } /* Z Y X order */
+        else if (x0 < z0) {
+            i1 = 0;
+            j1 = 1;
+            k1 = 0;
+            i2 = 0;
+            j2 = 1;
+            k2 = 1;
+        } /* Y Z X order */
+        else {
+            i1 = 0;
+            j1 = 1;
+            k1 = 0;
+            i2 = 1;
+            j2 = 1;
+            k2 = 0;
+        } /* Y X Z order */
+    }
+    /* A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z),
+       a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and
+       a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where
+       c = 1/6. */
+    double x1 = x0 - i1 + _G3; /* Offsets for second corner in (x,y,z) coords */
+    double y1 = y0 - j1 + _G3;
+    double z1 = z0 - k1 + _G3;
+    double x2 = x0 - i2 + 2.0 * _G3; /* Offsets for third corner in (x,y,z) coords */
+    double y2 = y0 - j2 + 2.0 * _G3;
+    double z2 = z0 - k2 + 2.0 * _G3;
+    double x3 = x0 - 1.0 + 3.0 * _G3; /* Offsets for last corner in (x,y,z) coords */
+    double y3 = y0 - 1.0 + 3.0 * _G3;
+    double z3 = z0 - 1.0 + 3.0 * _G3;
+    /* Work out the hashed gradient indices of the four simplex corners */
+    int ii = i & 255;
+    int jj = j & 255;
+    int kk = k & 255;
+    int gi0 = _permutationsMod12[ii + _permutations2[jj + _permutations2[kk]]];
+    int gi1 = _permutationsMod12[ii + i1 + _permutations2[jj + j1 + _permutations2[kk + k1]]];
+    int gi2 = _permutationsMod12[ii + i2 + _permutations2[jj + j2 + _permutations2[kk + k2]]];
+    int gi3 = _permutationsMod12[ii + 1 + _permutations2[jj + 1 + _permutations2[kk + 1]]];
+    /* Calculate the contribution from the four corners */
+    double t0 = 0.6 - x0 * x0 - y0 * y0 - z0 * z0;
+    if (t0 < 0)
+        n0 = 0.0;
+    else {
+        t0 *= t0;
+        n0 = t0 * t0 * _dot3(_grad3[gi0], x0, y0, z0);
+    }
+    double t1 = 0.6 - x1 * x1 - y1 * y1 - z1 * z1;
+    if (t1 < 0)
+        n1 = 0.0;
+    else {
+        t1 *= t1;
+        n1 = t1 * t1 * _dot3(_grad3[gi1], x1, y1, z1);
+    }
+    double t2 = 0.6 - x2 * x2 - y2 * y2 - z2 * z2;
+    if (t2 < 0)
+        n2 = 0.0;
+    else {
+        t2 *= t2;
+        n2 = t2 * t2 * _dot3(_grad3[gi2], x2, y2, z2);
+    }
+    double t3 = 0.6 - x3 * x3 - y3 * y3 - z3 * z3;
+    if (t3 < 0)
+        n3 = 0.0;
+    else {
+        t3 *= t3;
+        n3 = t3 * t3 * _dot3(_grad3[gi3], x3, y3, z3);
+    }
+    /* Add contributions from each corner to get the final noise value.
+       The result is scaled to stay just inside [-0.5,0.5] */
+    return 16.0 * (n0 + n1 + n2 + n3);
 }
 
 static constexpr double TEXTURE_SCALING = 15.0;