attr/m48894: introduce neighbour bias LoD predictor construction

This adoption allows determining the weights of each point's
predicting neighbours with a reduced influence of the, for
instance, z component.

cfg/octree-liftt-ctc-lossless-geom-lossy-attrs.yaml

@@ -36,6 +36,7 @@ categories:
      -
        - !conditional '"${group}" =~ m{^cat3}'
        - lodDecimation: 1
+       - lod_neigh_bias: ${seq_lod_bias}
 
      ##
      # attribute coding -- reflectance

cfg/octree-liftt-ctc-lossy-geom-lossy-attrs.yaml

@@ -45,6 +45,7 @@ categories:
        -
          - !conditional '"${group}" =~ m{^cat3}'
          - lodDecimation: 1
+         - lod_neigh_bias: ${seq_lod_bias}
 
        ##
        # attribute coding -- reflectance

cfg/octree-predt-ctc-lossless-geom-lossless-attrs.yaml

@@ -39,6 +39,7 @@ categories:
        -
          - !conditional '"${group}" =~ m{^cat3}'
          - levelOfDetailCount: 0
+         - lod_neigh_bias: ${seq_lod_bias}
        - positionQuantizationScaleAdjustsDist2: 1
        - dist2: ${seq_dist2}
        - intraLodPredictionEnabled: 1

cfg/octree-predt-ctc-lossless-geom-nearlossless-attrs.yaml

@@ -35,6 +35,7 @@ categories:
      -
        - !conditional '"${group}" =~ m{^cat3}'
        - levelOfDetailCount: 0
+       - lod_neigh_bias: ${seq_lod_bias}
      - positionQuantizationScaleAdjustsDist2: 1
      - dist2: ${seq_dist2}
      - intraLodPredictionEnabled: 1

cfg/sequences-cat3.yaml

@@ -8,6 +8,7 @@ sequences:
     # precision is actually (21, 20, 16)
     src-geometry-precision: 21
     seq_lod: 10
+    seq_lod_bias: '1,1,2'
     seq_dist2: 8192
     has_refl: 1
     has_colour: 1
@@ -23,6 +24,7 @@ sequences:
     # precision is actually (20, 20, 16)
     src-geometry-precision: 20
     seq_lod: 10
+    seq_lod_bias: '1,1,2'
     seq_dist2: 16384
     has_refl: 1
     has_colour: 1
@@ -38,6 +40,7 @@ sequences:
     # precision is actually (21, 20, 17)
     src-geometry-precision: 21
     seq_lod: 10
+    seq_lod_bias: '1,1,2'
     seq_dist2: 16384
     has_refl: 1
     has_colour: 1
@@ -57,6 +60,7 @@ sequences:
     group: cat3-frame
     src-geometry-precision: 18
     seq_lod: 10
+    seq_lod_bias: '1,1,8'
     seq_dist2: 16384
     has_refl: 1
     bitdepth_refl: 8
@@ -72,6 +76,7 @@ sequences:
     group: cat3-frame
     src-geometry-precision: 18
     seq_lod: 10
+    seq_lod_bias: '1,1,8'
     seq_dist2: 16384
     has_refl: 1
     bitdepth_refl: 8
@@ -87,6 +92,7 @@ sequences:
     group: cat3-frame
     src-geometry-precision: 18
     seq_lod: 10
+    seq_lod_bias: '1,1,8'
     seq_dist2: 16384
     has_refl: 1
     bitdepth_refl: 8
@@ -104,6 +110,7 @@ sequences:
     group: cat3-frame
     src-geometry-precision: 18
     seq_lod: 10
+    seq_lod_bias: '1,1,8'
     seq_dist2: 16384
     has_refl: 1
     bitdepth_refl: 8
@@ -121,6 +128,7 @@ sequences:
     group: cat3-frame
     src-geometry-precision: 18
     seq_lod: 10
+    seq_lod_bias: '1,1,8'
     seq_dist2: 16384
     has_refl: 1
     bitdepth_refl: 8
@@ -138,6 +146,7 @@ sequences:
     group: cat3-frame
     src-geometry-precision: 18
     seq_lod: 10
+    seq_lod_bias: '1,1,8'
     seq_dist2: 16384
     has_refl: 1
     bitdepth_refl: 8
@@ -155,6 +164,7 @@ sequences:
     group: cat3-frame
     src-geometry-precision: 18
     seq_lod: 10
+    seq_lod_bias: '1,1,8'
     seq_dist2: 16384
     has_refl: 1
     bitdepth_refl: 8

cfg/trisoup-liftt-ctc-lossy-geom-lossy-attrs.yaml

@@ -36,6 +36,7 @@ categories:
      -
        - !conditional '"${group}" =~ m{^cat3}'
        - lodDecimation: 1
+       - lod_neigh_bias: ${seq_lod_bias}
      - positionQuantizationScaleAdjustsDist2: 1
      - dist2: ${seq_dist2}
 

doc/README.options.md

@@ -348,6 +348,11 @@ Attribute's number of levels of detail.
 Attribute's list of squared distances, or initial value for automatic
 derivation.
 
+### `--lod_neigh_bias=INT-VALUE-LIST`
+A set of three bias factors corresponding to the first, second and third
+geometry axes used to weight nearest neighbours during the LoD generation
+and weighting processes.  The value `1,1,1` implies no bias.
+
 ### `--qp=INT-VALUE`
 Attribute's luma quantization parameter.
 

tmc3/PCCMath.h

@@ -331,6 +331,16 @@ struct Box3 {
   }
 };
 
+//---------------------------------------------------------------------------
+// element-wise multiplication of two vectors
+
+template<typename T>
+Vec3<T>
+times(Vec3<T> lhs, const Vec3<T>& rhs)
+{
+  return Vec3<T>{lhs[0] * rhs[0], lhs[1] * rhs[1], lhs[2] * rhs[2]};
+}
+
 //---------------------------------------------------------------------------
 
 typedef DEPRECATED_MSVC Vec3<double> PCCVector3D DEPRECATED;

tmc3/PCCTMC3Common.h

@@ -666,7 +666,7 @@ computeNearestNeighbors(
         aps.scalable_lifting_enabled_flag, nodeSizeLog2,
         pointCloud[pointIndex1]);
 
-      double norm2 = (point - point1).getNorm2();
+      double norm2 = times(point - point1, aps.lod_neigh_bias).getNorm2();
       if (nodeSizeLog2 > 0 && point == point1) {
         norm2 = double(1 << (nodeSizeLog2 - 1));
         norm2 = norm2 * norm2;
@@ -696,7 +696,8 @@ computeNearestNeighbors(
               aps.scalable_lifting_enabled_flag, nodeSizeLog2,
               pointCloud[pointIndex1]);
 
-            double norm2 = (point - point1).getNorm2();
+            double norm2 =
+              times(point - point1, aps.lod_neigh_bias).getNorm2();
             if (nodeSizeLog2 > 0 && point == point1) {
               norm2 = (double)(1 << (nodeSizeLog2 - 1));
               norm2 = norm2 * norm2;
@@ -720,7 +721,7 @@ computeNearestNeighbors(
         const int32_t pointIndex1 = packedVoxel[indexes[startIndex + k]].index;
         const auto& point1 = pointCloud[pointIndex1];
         predictor.insertNeighbor(
-          pointIndex1, (point - point1).getNorm2(),
+          pointIndex1, times(point - point1, aps.lod_neigh_bias).getNorm2(),
           aps.num_pred_nearest_neighbours,
           startIndex + k - i + 2 * aps.search_range);
       }
@@ -742,7 +743,8 @@ computeNearestNeighbors(
               packedVoxel[indexes[startIndex + k]].index;
             const auto& point1 = pointCloud[pointIndex1];
             predictor.insertNeighbor(
-              pointIndex1, (point - point1).getNorm2(),
+              pointIndex1,
+              times(point - point1, aps.lod_neigh_bias).getNorm2(),
               aps.num_pred_nearest_neighbours,
               startIndex + k - i + 2 * aps.search_range);
           }

tmc3/TMC3.cpp

@@ -556,6 +556,10 @@ ParseParameters(int argc, char* argv[], Parameters& params)
     params_attr.aps.search_range, 128,
     "Range for nearest neighbor search")
 
+  ("lod_neigh_bias",
+    params_attr.aps.lod_neigh_bias, {1, 1, 1},
+    "Attribute's intra prediction weight for Z axis")
+
   ("lodDecimation",
     params_attr.aps.lod_decimation_enabled_flag, false,
     "Controls LoD generation method:\n"

tmc3/hls.h

@@ -279,6 +279,7 @@ struct AttributeParameterSet {
   int max_num_direct_predictors;
   int adaptive_prediction_threshold;
   int search_range;
+  Vec3<double> lod_neigh_bias;
   bool intra_lod_prediction_enabled_flag;
 
   // NB: derived from num_detail_levels_minus1

tmc3/io_hls.cpp

@@ -278,6 +278,9 @@ write(const AttributeParameterSet& aps)
   if (isLifting) {
     bs.writeUe(aps.num_pred_nearest_neighbours);
     bs.writeUe(aps.num_detail_levels);
+    bs.writeUe(aps.lod_neigh_bias.x());
+    bs.writeUe(aps.lod_neigh_bias.y());
+    bs.writeUe(aps.lod_neigh_bias.z());
 
     if (aps.attr_encoding == AttributeEncoding::kLiftingTransform)
       bs.write(aps.scalable_lifting_enabled_flag);
@@ -333,6 +336,9 @@ parseAps(const PayloadBuffer& buf)
   if (isLifting) {
     bs.readUe(&aps.num_pred_nearest_neighbours);
     bs.readUe(&aps.num_detail_levels);
+    bs.readUe(&aps.lod_neigh_bias.x());
+    bs.readUe(&aps.lod_neigh_bias.y());
+    bs.readUe(&aps.lod_neigh_bias.z());
 
     aps.scalable_lifting_enabled_flag = false;
     if (aps.attr_encoding == AttributeEncoding::kLiftingTransform)