got rid of buildnumber.c and buildnum program, now uses builddate.c (touched each...

[xonotic/darkplaces.git] / fractalnoise.c

diff --git a/fractalnoise.c b/fractalnoise.c
index 31b140d518972459b866a85687df6722d056efa3..ad9d91ed4a0ab1b0a4bf7a396483c3047f8bc987 100644 (file)
--- a/fractalnoise.c
+++ b/fractalnoise.c
@@ -63,3 +63,50 @@ void fractalnoise(byte *noise, int size, int startgrid)
        Mem_Free(noisebuf);
 #undef n
 }
+
+// unnormalized, used for explosions mainly, does not allocate/free memory (hence the name quick)
+void fractalnoisequick(byte *noise, int size, int startgrid)
+{
+       int x, y, g, g2, amplitude, size1 = size - 1, sizepower, gridpower;
+#define n(x,y) noise[((y)&size1)*size+((x)&size1)]
+
+       for (sizepower = 0;(1 << sizepower) < size;sizepower++);
+       if (size != (1 << sizepower))
+               Sys_Error("fractalnoise: size must be power of 2\n");
+
+       for (gridpower = 0;(1 << gridpower) < startgrid;gridpower++);
+       if (startgrid != (1 << gridpower))
+               Sys_Error("fractalnoise: grid must be power of 2\n");
+
+       startgrid = bound(0, startgrid, size);
+
+       amplitude = 255; // this gets halved before use
+       memset(noise, 0, size*size);
+
+       for (g2 = startgrid;g2;g2 >>= 1)
+       {
+               // brownian motion (at every smaller level there is random behavior)
+               amplitude >>= 1;
+               for (y = 0;y < size;y += g2)
+                       for (x = 0;x < size;x += g2)
+                               n(x,y) += (rand()&amplitude);
+
+               g = g2 >> 1;
+               if (g)
+               {
+                       // subdivide, diamond-square algorythm (really this has little to do with squares)
+                       // diamond
+                       for (y = 0;y < size;y += g2)
+                               for (x = 0;x < size;x += g2)
+                                       n(x+g,y+g) = (byte) (((int) n(x,y) + (int) n(x+g2,y) + (int) n(x,y+g2) + (int) n(x+g2,y+g2)) >> 2);
+                       // square
+                       for (y = 0;y < size;y += g2)
+                               for (x = 0;x < size;x += g2)
+                               {
+                                       n(x+g,y) = (byte) (((int) n(x,y) + (int) n(x+g2,y) + (int) n(x+g,y-g) + (int) n(x+g,y+g)) >> 2);
+                                       n(x,y+g) = (byte) (((int) n(x,y) + (int) n(x,y+g2) + (int) n(x-g,y+g) + (int) n(x+g,y+g)) >> 2);
+                               }
+               }
+       }
+#undef n
+}