implement growing saplings with bone meal

src/structures.c

@@ -0,0 +1,55 @@
+#include <stdlib.h>
+
+#include "globals.h"
+#include "tools.h"
+#include "registries.h"
+#include "worldgen.h"
+#include "procedures.h"
+#include "structures.h"
+
+void setBlockIfReplaceable (short x, uint8_t y, short z, uint8_t block) {
+  if (!isReplaceableBlock(getBlockAt(x, y, z))) return;
+  makeBlockChange(x, y, z, block);
+}
+
+// Places a tree centered on the input coordinates
+void placeTreeStructure (short x, uint8_t y, short z) {
+
+  // Get a random number for tree height and leaf edges
+  uint32_t r = fast_rand();
+  uint8_t height = 4 + (r % 3);
+
+  // Set tree base - replace sapling with log and put dirt below
+  makeBlockChange(x, y - 1, z, B_dirt);
+  makeBlockChange(x, y, z, B_oak_log);
+  // Create tree stump
+  for (int i = 1; i < height; i ++) {
+    setBlockIfReplaceable(x, y + i, z, B_oak_log);
+  }
+  // Keep track of leaf corners, determines random number bit shift
+  uint8_t t = 2;
+  // First (bottom) leaf layer
+  for (int i = -2; i <= 2; i ++) {
+    for (int j = -2; j <= 2; j ++) {
+      setBlockIfReplaceable(x + i, y + height - 3, z + j, B_oak_leaves);
+      // Randomly skip some corners, emulating vanilla tree shape
+      if ((i == 2 || i == -2) && (j == 2 || j == -2)) {
+        t ++;
+        if ((r >> t) & 1) continue;
+      }
+      setBlockIfReplaceable(x + i, y + height - 2, z + j, B_oak_leaves);
+    }
+  }
+  // Second (top) leaf layer
+  for (int i = -1; i <= 1; i ++) {
+    for (int j = -1; j <= 1; j ++) {
+      setBlockIfReplaceable(x + i, y + height - 1, z + j, B_oak_leaves);
+      if ((i == 1 || i == -1) && (j == 1 || j == -1)) {
+        t ++;
+        if ((r >> t) & 1) continue;
+      }
+      setBlockIfReplaceable(x + i, y + height, z + j, B_oak_leaves);
+    }
+  }
+
+}