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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.
//
#include "draco/compression/mesh/mesh_sequential_encoder.h"
#include <cstdlib>
#include "draco/compression/attributes/linear_sequencer.h"
#include "draco/compression/attributes/sequential_attribute_encoders_controller.h"
#include "draco/compression/entropy/symbol_encoding.h"
#include "draco/core/varint_encoding.h"
namespace draco {
MeshSequentialEncoder::MeshSequentialEncoder() {}
Status MeshSequentialEncoder::EncodeConnectivity() {
// Serialize indices.
const uint32_t num_faces = mesh()->num_faces();
EncodeVarint(num_faces, buffer());
EncodeVarint(static_cast<uint32_t>(mesh()->num_points()), buffer());
// We encode all attributes in the original (possibly duplicated) format.
// TODO(ostava): This may not be optimal if we have only one attribute or if
// all attributes share the same index mapping.
if (options()->GetGlobalBool("compress_connectivity", false)) {
// 0 = Encode compressed indices.
buffer()->Encode(static_cast<uint8_t>(0));
if (!CompressAndEncodeIndices()) {
return Status(Status::DRACO_ERROR, "Failed to compress connectivity.");
}
} else {
// 1 = Encode indices directly.
buffer()->Encode(static_cast<uint8_t>(1));
// Store vertex indices using a smallest data type that fits their range.
// TODO(ostava): This can be potentially improved by using a tighter
// fit that is not bound by a bit-length of any particular data type.
if (mesh()->num_points() < 256) {
// Serialize indices as uint8_t.
for (FaceIndex i(0); i < num_faces; ++i) {
const auto &face = mesh()->face(i);
buffer()->Encode(static_cast<uint8_t>(face[0].value()));
buffer()->Encode(static_cast<uint8_t>(face[1].value()));
buffer()->Encode(static_cast<uint8_t>(face[2].value()));
}
} else if (mesh()->num_points() < (1 << 16)) {
// Serialize indices as uint16_t.
for (FaceIndex i(0); i < num_faces; ++i) {
const auto &face = mesh()->face(i);
buffer()->Encode(static_cast<uint16_t>(face[0].value()));
buffer()->Encode(static_cast<uint16_t>(face[1].value()));
buffer()->Encode(static_cast<uint16_t>(face[2].value()));
}
} else if (mesh()->num_points() < (1 << 21)) {
// Serialize indices as varint.
for (FaceIndex i(0); i < num_faces; ++i) {
const auto &face = mesh()->face(i);
EncodeVarint(static_cast<uint32_t>(face[0].value()), buffer());
EncodeVarint(static_cast<uint32_t>(face[1].value()), buffer());
EncodeVarint(static_cast<uint32_t>(face[2].value()), buffer());
}
} else {
// Serialize faces as uint32_t (default).
for (FaceIndex i(0); i < num_faces; ++i) {
const auto &face = mesh()->face(i);
buffer()->Encode(face);
}
}
}
return OkStatus();
}
bool MeshSequentialEncoder::GenerateAttributesEncoder(int32_t att_id) {
// Create only one attribute encoder that is going to encode all points in a
// linear sequence.
if (att_id == 0) {
// Create a new attribute encoder only for the first attribute.
AddAttributesEncoder(std::unique_ptr<AttributesEncoder>(
new SequentialAttributeEncodersController(
std::unique_ptr<PointsSequencer>(
new LinearSequencer(point_cloud()->num_points())),
att_id)));
} else {
// Reuse the existing attribute encoder for other attributes.
attributes_encoder(0)->AddAttributeId(att_id);
}
return true;
}
bool MeshSequentialEncoder::CompressAndEncodeIndices() {
// Collect all indices to a buffer and encode them.
// Each new index is a difference from the previous value.
std::vector<uint32_t> indices_buffer;
int32_t last_index_value = 0;
const int num_faces = mesh()->num_faces();
for (FaceIndex i(0); i < num_faces; ++i) {
const auto &face = mesh()->face(i);
for (int j = 0; j < 3; ++j) {
const int32_t index_value = face[j].value();
const int32_t index_diff = index_value - last_index_value;
// Encode signed value to an unsigned one (put the sign to lsb pos).
const uint32_t encoded_val =
(abs(index_diff) << 1) | (index_diff < 0 ? 1 : 0);
indices_buffer.push_back(encoded_val);
last_index_value = index_value;
}
}
EncodeSymbols(indices_buffer.data(), static_cast<int>(indices_buffer.size()),
1, nullptr, buffer());
return true;
}
void MeshSequentialEncoder::ComputeNumberOfEncodedPoints() {
set_num_encoded_points(mesh()->num_points());
}
void MeshSequentialEncoder::ComputeNumberOfEncodedFaces() {
set_num_encoded_faces(mesh()->num_faces());
}
} // namespace draco
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