Example rendering

src/rpg/world/worldunit.c

@@ -0,0 +1,39 @@
+/**
+ * Copyright (c) 2025 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "worldunit.h"
+#include "assert/assert.h"
+
+void worldChunkPosAdd(
+  worldchunkpos_t *pos,
+  const worldsubtile_t amt
+) {
+  int8_t a = pos->subtile; // current signed subtile
+  int8_t b = amt; // signed delta
+  uint8_t unsignedAdded = (uint8_t)a + (uint8_t)b; // well-defined wrap add
+  int8_t  r = (int8_t)unsignedAdded; // result in signed domain
+
+  pos->subtile = r;
+
+  // Signed-overflow detection for a + b -> r:
+  // overflow if sign(a) == sign(b) and sign(r) != sign(a)
+  uint8_t ov = (uint8_t)((a ^ r) & (b ^ r)) >> 7;   // 1 if overflow, else 0
+
+  // Direction of carry: +1 for b >= 0, -1 for b < 0 (computed branchlessly)
+  uint8_t neg = ((uint8_t)b) >> 7;                  // 0 if b>=0, 1 if b<0
+  int8_t  dir = (int8_t)(1 - (neg << 1));           // +1 or -1
+
+  // Apply tile adjustment (mod-256 via uint8_t arithmetic)
+  pos->tile = (uint8_t)(pos->tile + (uint8_t)(ov * (uint8_t)dir));
+}
+
+float_t worldChunkPosToF32(
+  const worldchunkpos_t pos,
+  const uint8_t tileSize
+) {
+  return (float_t)(pos.tile * tileSize) + ((float_t)pos.subtile / 256.0f);
+}