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Differential D4501 Diff 14677 extern/draco/dracoenc/src/draco/compression/mesh/mesh_edgebreaker_traversal_valence_encoder.h

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extern/draco/dracoenc/src/draco/compression/mesh/mesh_edgebreaker_traversal_valence_encoder.h

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// Copyright 2016 The Draco Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#ifndef DRACO_COMPRESSION_MESH_MESH_EDGEBREAKER_TRAVERSAL_VALENCE_ENCODER_H_
#define DRACO_COMPRESSION_MESH_MESH_EDGEBREAKER_TRAVERSAL_VALENCE_ENCODER_H_
#include "draco/compression/entropy/symbol_encoding.h"
#include "draco/compression/mesh/mesh_edgebreaker_traversal_encoder.h"
#include "draco/core/varint_encoding.h"
namespace draco {
// Predictive encoder for the Edgebreaker symbols based on valences of the
// previously encoded vertices, following the method described in: Szymczak'02,
// "Optimized Edgebreaker Encoding for Large and Regular Triangle Meshes". Each
// valence is used to specify a different entropy context for encoding of the
// symbols.
// Encoder can operate in various predefined modes that can be used to select
// the way in which the entropy contexts are computed (e.g. using different
// clamping for valences, or even using different inputs to compute the
// contexts), see EdgebreakerValenceCodingMode in mesh_edgebreaker_shared.h for
// a list of supported modes.
class MeshEdgebreakerTraversalValenceEncoder
: public MeshEdgebreakerTraversalEncoder {
public:
MeshEdgebreakerTraversalValenceEncoder()
: corner_table_(nullptr),
prev_symbol_(-1),
last_corner_(kInvalidCornerIndex),
num_symbols_(0),
min_valence_(2),
max_valence_(7) {}
bool Init(MeshEdgebreakerEncoderImplInterface *encoder) {
if (!MeshEdgebreakerTraversalEncoder::Init(encoder))
return false;
min_valence_ = 2;
max_valence_ = 7;
corner_table_ = encoder->GetCornerTable();
// Initialize valences of all vertices.
vertex_valences_.resize(corner_table_->num_vertices());
for (VertexIndex i(0); i < static_cast<uint32_t>(vertex_valences_.size());
++i) {
vertex_valences_[i] = corner_table_->Valence(VertexIndex(i));
}
// Replicate the corner to vertex map from the corner table. We need to do
// this because the map may get updated during encoding because we add new
// vertices when we encounter split symbols.
corner_to_vertex_map_.resize(corner_table_->num_corners());
for (CornerIndex i(0); i < corner_table_->num_corners(); ++i) {
corner_to_vertex_map_[i] = corner_table_->Vertex(i);
}
const int32_t num_unique_valences = max_valence_ - min_valence_ + 1;
context_symbols_.resize(num_unique_valences);
return true;
}
inline void NewCornerReached(CornerIndex corner) { last_corner_ = corner; }
inline void EncodeSymbol(EdgebreakerTopologyBitPattern symbol) {
++num_symbols_;
// Update valences on the mesh and compute the context that is going to be
// used to encode the processed symbol.
// Note that the valences are computed for the so far unencoded part of the
// mesh (i.e. the decoding is reverse). Adding a new symbol either reduces
// valences on the vertices or leaves the valence unchanged.
const CornerIndex next = corner_table_->Next(last_corner_);
const CornerIndex prev = corner_table_->Previous(last_corner_);
// Get valence on the tip corner of the active edge (outgoing edge that is
// going to be used in reverse decoding of the connectivity to predict the
// next symbol).
const int active_valence = vertex_valences_[corner_to_vertex_map_[next]];
switch (symbol) {
case TOPOLOGY_C:
// Compute prediction.
FALLTHROUGH_INTENDED;
case TOPOLOGY_S:
// Update valences.
vertex_valences_[corner_to_vertex_map_[next]] -= 1;
vertex_valences_[corner_to_vertex_map_[prev]] -= 1;
if (symbol == TOPOLOGY_S) {
// Whenever we reach a split symbol, we need to split the vertex into
// two and attach all corners on the left and right sides of the split
// vertex to the respective vertices (see image below). This is
// necessary since the decoder works in the reverse order and it
// merges the two vertices only after the split symbol is processed.
//
// * -----
// / \--------
// / \--------
// / \-------
// *-------v-------*
// \ /c\ /
// \ / \ /
// \ /n S p\ /
// *.......*
//
// Count the number of faces on the left side of the split vertex and
// update the valence on the "left vertex".
int num_left_faces = 0;
CornerIndex act_c = corner_table_->Opposite(prev);
while (act_c != kInvalidCornerIndex) {
if (encoder_impl()->IsFaceEncoded(corner_table_->Face(act_c)))
break; // Stop when we reach the first visited face.
++num_left_faces;
act_c = corner_table_->Opposite(corner_table_->Next(act_c));
}
vertex_valences_[corner_to_vertex_map_[last_corner_]] =
num_left_faces + 1;
// Create a new vertex for the right side and count the number of
// faces that should be attached to this vertex.
const int new_vert_id = static_cast<int>(vertex_valences_.size());
int num_right_faces = 0;
act_c = corner_table_->Opposite(next);
while (act_c != kInvalidCornerIndex) {
if (encoder_impl()->IsFaceEncoded(corner_table_->Face(act_c)))
break; // Stop when we reach the first visited face.
++num_right_faces;
// Map corners on the right side to the newly created vertex.
corner_to_vertex_map_[corner_table_->Next(act_c)] = new_vert_id;
act_c = corner_table_->Opposite(corner_table_->Previous(act_c));
}
vertex_valences_.push_back(num_right_faces + 1);
}
break;
case TOPOLOGY_R:
// Update valences.
vertex_valences_[corner_to_vertex_map_[last_corner_]] -= 1;
vertex_valences_[corner_to_vertex_map_[next]] -= 1;
vertex_valences_[corner_to_vertex_map_[prev]] -= 2;
break;
case TOPOLOGY_L:
vertex_valences_[corner_to_vertex_map_[last_corner_]] -= 1;
vertex_valences_[corner_to_vertex_map_[next]] -= 2;
vertex_valences_[corner_to_vertex_map_[prev]] -= 1;
break;
case TOPOLOGY_E:
vertex_valences_[corner_to_vertex_map_[last_corner_]] -= 2;
vertex_valences_[corner_to_vertex_map_[next]] -= 2;
vertex_valences_[corner_to_vertex_map_[prev]] -= 2;
break;
default:
break;
}
if (prev_symbol_ != -1) {
int clamped_valence;
if (active_valence < min_valence_) {
clamped_valence = min_valence_;
} else if (active_valence > max_valence_) {
clamped_valence = max_valence_;
} else {
clamped_valence = active_valence;
}
const int context = clamped_valence - min_valence_;
context_symbols_[context].push_back(
edge_breaker_topology_to_symbol_id[prev_symbol_]);
}
prev_symbol_ = symbol;
}
void Done() {
// Store the init face configurations and attribute seam data
MeshEdgebreakerTraversalEncoder::EncodeStartFaces();
MeshEdgebreakerTraversalEncoder::EncodeAttributeSeams();
// Store the contexts.
for (int i = 0; i < context_symbols_.size(); ++i) {
EncodeVarint<uint32_t>(static_cast<uint32_t>(context_symbols_[i].size()),
GetOutputBuffer());
if (context_symbols_[i].size() > 0) {
EncodeSymbols(context_symbols_[i].data(),
static_cast<int>(context_symbols_[i].size()), 1, nullptr,
GetOutputBuffer());
}
}
}
int NumEncodedSymbols() const { return num_symbols_; }
private:
const CornerTable *corner_table_;
// Explicit map between corners and vertices. We cannot use the one stored
// in the |corner_table_| because we may need to add additional vertices to
// handle split symbols.
IndexTypeVector<CornerIndex, VertexIndex> corner_to_vertex_map_;
IndexTypeVector<VertexIndex, int> vertex_valences_;
// Previously encoded symbol.
int32_t prev_symbol_;
CornerIndex last_corner_;
// Explicitly count the number of encoded symbols.
int num_symbols_;
int min_valence_;
int max_valence_;
std::vector<std::vector<uint32_t>> context_symbols_;
};
} // namespace draco
#endif // DRACO_COMPRESSION_MESH_MESH_EDGEBREAKER_TRAVERSAL_VALENCE_ENCODER_H_