Bug in buildHashAllocAndVisibleTypePP: offset missing.

[Algomorph]

Because your voxel coordinates represent voxel centers, i.e. they're projected directly onto the image and then rounded to get the depth, your actual hash blocks actually start with a 1/2 voxel offset from the whole coordinate.

You don't take this into account when allocating hash blocks, which results in missing blocks in certain situations and contributes drift/noise. The easy fix is to add the offset to the segment along camera ray that's marched on during hash block allocation.

Simply replace these lines:

InfiniTAM/InfiniTAM/ITMLib/Engines/Reconstruction/Shared/ITMSceneReconstructionEngine_Shared.h

Lines 202 to 206 in 4156547

	pt_buff = pt_camera_f * (1.0f - mu / norm); pt_buff.w = 1.0f;
	point = TO_VECTOR3(invM_d * pt_buff) * oneOverVoxelSize;
	pt_buff = pt_camera_f * (1.0f + mu / norm); pt_buff.w = 1.0f;
	point_e = TO_VECTOR3(invM_d * pt_buff) * oneOverVoxelSize;

With this:

        pt_buff = pt_camera_f * (1.0f - mu / norm); pt_buff.w = 1.0f;
	point = TO_VECTOR3(invM_d * pt_buff) * oneOverVoxelSize + Vector3f(1.0f / (2.0f * VOXEL_BLOCK_SIZE));

	pt_buff = pt_camera_f * (1.0f + mu / norm); pt_buff.w = 1.0f;
	point_e = TO_VECTOR3(invM_d * pt_buff) * oneOverVoxelSize + Vector3f(1.0f / (2.0f * VOXEL_BLOCK_SIZE));

Also, your variable names could be a bit more descriptive and not use acronyms, and calling the inverse of hash block size in meters "oneOverVoxelSize" is misleading. I suggest "oneOverVoxelBlockSize_Meters".

[Mad-Thanos]

VOXEL_BLOCK_SIZE

Hi, @ Algomorph What is VOXEL_BLOCK_SIZE in your code?

[Algomorph]

@GucciPrada ,

In my code,

these lines

#define VOXEL_BLOCK_SIZE 8
// VOXEL_BLOCK_SIZE3 = VOXEL_BLOCK_SIZE * VOXEL_BLOCK_SIZE * VOXEL_BLOCK_SIZE
#define VOXEL_BLOCK_SIZE3 512

correspond to these lines in the original InfiniTAM repo:

InfiniTAM/InfiniTAM/ITMLib/Objects/Scene/ITMVoxelBlockHash.h

Lines 15 to 16 in 4156547

	#define SDF_BLOCK_SIZE 8 // SDF block size
	#define SDF_BLOCK_SIZE3 512 // SDF_BLOCK_SIZE3 = SDF_BLOCK_SIZE * SDF_BLOCK_SIZE * SDF_BLOCK_SIZE

Since I have other kinds of voxels beside TSDF, it didn't make sense to refer to voxel hash blocks as "SDF blocks", so I refactored these and other things accordingly.