Function GetBridgeItemIntersect

TombEngine/Game/collision/floordata.cpp:763–819

TODO: Load anim frame AABBs as DX BoundingBox objects and do regular ray test for gain of 3-5 frames. -- Sezz 2024.11.07 TODO: Try querying collision mesh instead. Get precise floor/ceiling height from object's bounding box. Animated objects are also supported, although horizontal collision shifting is unstable. Method: get accurate bounds in world transform by converting to OBB, then do a ray tes

	// Method: get accurate bounds in world transform by converting to OBB, then do a ray test
	// on top or bottom (depending on test side) to determine if box is present at a particular point.
	std::optional<int> GetBridgeItemIntersect(const ItemInfo& item, const Vector3i& pos, bool useBottomHeight)
	{
		constexpr auto VERTICAL_MARGIN = 4;

		// Check bridge cache for existing entry.
		for (const auto& entry : BridgeCache) 
		{
			if (entry.BridgeItemNumber == item.Index && entry.BridgePose == item.Pose && 
				entry.UseBottomHeight == useBottomHeight && entry.Position == pos)
			{
				return entry.Height;
			}
		}

		auto box = GameBoundingBox(&item);
		auto extents = box.GetExtents();

		// Test rough circle intersection to discard bridges not intersecting on XZ plane.
		auto circle1 = Vector3(pos.x, pos.z, BLOCK(1));
		auto circle2 = Vector3(item.Pose.Position.x, item.Pose.Position.z, std::hypot(extents.x, extents.z));

		auto height = std::optional<int>();
		if (Geometry::CircleIntersects(circle1, circle2))
		{
			auto origin = Vector3i(pos.x, pos.y + (useBottomHeight ? VERTICAL_MARGIN : -VERTICAL_MARGIN), pos.z) - item.Pose.Position;

			float sinAngle = phd_sin(item.Pose.Orientation.y);
			float cosAngle = phd_cos(item.Pose.Orientation.y);

			auto localOrigin = Vector3i(
				(origin.x * cosAngle) - (origin.z * sinAngle),
				origin.y,
				(origin.x * sinAngle) + (origin.z * cosAngle));

			// Calculate intersection distance.
			auto direction = useBottomHeight ? -Vector3::UnitY : Vector3::UnitY;
			float targetY = useBottomHeight ? box.Y2 : box.Y1;
			float dist = (targetY - localOrigin.y) / direction.y;

			// Compute intersection point.
			auto intersectionPoint = Geometry::TranslatePoint(localOrigin, direction, dist);

			// Check if intersection point is within bounding box's X and Z extents.
			if (intersectionPoint.x >= box.X1 && intersectionPoint.x <= box.X2 &&
				intersectionPoint.z >= box.Z1 && intersectionPoint.z <= box.Z2)
			{
				// Transform intersection point back to world coordinates.
				height = item.Pose.Position.y + intersectionPoint.y;
			}
		}

		// Cache bridge data.
		BridgeCache[BridgeCacheSlotID] = BridgeCacheEntry{ item.Index, item.Pose, useBottomHeight, pos, height };
		BridgeCacheSlotID = (BridgeCacheSlotID + 1) % BRIDGE_CACHE_SIZE; // Wrap to next slot ID.

		return height;
	}