Implement playable Mac client and rendering validation

extension/src/water_depth.h

@@ -0,0 +1,12 @@
+#pragma once
+#include <cmath>
+
+namespace mtgodot {
+// 40250 MapOutdoor.cpp / AreaTerrain.cpp. Arguments in scaled centimetres.
+inline float water_depth_alpha(double depth_cm, double height_scale) {
+	if (!std::isfinite(depth_cm) || !std::isfinite(height_scale) ||
+			height_scale <= 0.0 || depth_cm <= 0.0) return 0.0f;
+	double alpha = depth_cm / (400.0 * height_scale);
+	return static_cast<float>(alpha > 0.8 ? 0.8 : alpha);
+}
+}