ADD: Floating origin system

src/core/world.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <glm/vec3.hpp>
+
+#include <cmath>
+
+// Authoritative world-space coordinates are stored as double precision.
+using WorldVec3 = glm::dvec3;
+
+inline glm::vec3 world_to_local(const WorldVec3 &world, const WorldVec3 &origin_world)
+{
+    const WorldVec3 local_d = world - origin_world;
+    return glm::vec3(static_cast<float>(local_d.x),
+                     static_cast<float>(local_d.y),
+                     static_cast<float>(local_d.z));
+}
+
+inline WorldVec3 local_to_world(const glm::vec3 &local, const WorldVec3 &origin_world)
+{
+    return origin_world + WorldVec3(local);
+}
+
+inline WorldVec3 snap_world(const WorldVec3 &p, double grid_size)
+{
+    if (grid_size <= 0.0)
+    {
+        return p;
+    }
+
+    auto snap = [grid_size](double v) {
+        return std::round(v / grid_size) * grid_size;
+    };
+
+    return WorldVec3(snap(p.x), snap(p.y), snap(p.z));
+}
+