Decrease MAX_LOD to avoid potential integer overflows

I preferred doing this instead of using 64-bit integers,
because I tink there are no use cases for LOD blocks that big

constants/voxel_constants.h

@@ -14,7 +14,12 @@ static const unsigned int MAX_BLOCK_SIZE = 32;
 
 static const unsigned int MAX_BLOCK_COUNT_PER_REQUEST = 4 * 4 * 4;
 
-static const unsigned int MAX_LOD = 32;
+// 24 should be largely enough.
+// With a block size of 32 voxels, and if 1 voxel is 1m large,
+// then the largest blocks will span 268,435.456 kilometers, which is roughly 20 times Earth's diameter.
+// Using a higher maximum can cause int32 overflows when calculating dimensions. There is no use case for it.
+static const unsigned int MAX_LOD = 24;
+
 static const unsigned int MAX_VOLUME_EXTENT = 0x1fffffff;
 static const unsigned int MAX_VOLUME_SIZE = 2 * MAX_VOLUME_EXTENT; // 1,073,741,822 voxels
 

doc/source/changelog.md

@@ -40,6 +40,7 @@ Ongoing development - `master`
     - `VoxelInstanceGenerator`: `EMIT_FROM_FACES` got renamed `EMIT_FROM_FACES_FAST`. `EMIT_FROM_FACES` still exists but is a different algorithm.
     - `VoxelServer`: `get_stats()` format has changed, check documentation
     - `VoxelLodTerrain`: `get_statistics()` format has changed: `time_process_update_responses` and `remaining_main_thread_blocks` are no longer available
+    - `VoxelLodTerrain`: Maximum LOD count was decreased to 24, which is still largely enough. Higher maximums were likely to cause integer overflows.
     - `VoxelTerrain`: `get_statistics()` format has changed: `time_process_update_responses` and `remaining_main_thread_blocks` are no longer available
     - `VoxelViewer`: `requires_collisions` is now `true` by default
 

terrain/voxel_lod_terrain.cpp

@@ -356,6 +356,7 @@ void VoxelLodTerrain::_on_stream_params_changed() {
 }*/
 
 void VoxelLodTerrain::set_mesh_block_size(unsigned int mesh_block_size) {
+	// Mesh block size cannot be smaller than data block size, for now
 	mesh_block_size = clamp(mesh_block_size, get_data_block_size(), VoxelConstants::MAX_BLOCK_SIZE);
 
 	unsigned int po2;