+ val = eval(ms, x, y, z);
+ v.nx = eval(ms, x + VOX_DIST, y, z) - val;
+ v.ny = eval(ms, x, y + VOX_DIST, z) - val;
+ v.nz = eval(ms, x, y, z - VOX_DIST) - val;
+
+ if((len = sqrt(v.nx * v.nx + v.ny * v.ny + v.nz * v.nz)) != 0.0f) {
+ v.nx /= len;
+ v.ny /= len;
+ v.nz /= len;
+ }
+