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// Copyright 2017 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_ATTRIBUTES_PREDICTION_SCHEMES_MESH_PREDICTION_SCHEME_GEOMETRIC_NORMAL_PREDICTOR_AREA_H_
#define DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_MESH_PREDICTION_SCHEME_GEOMETRIC_NORMAL_PREDICTOR_AREA_H_
#include "draco/compression/attributes/prediction_schemes/mesh_prediction_scheme_geometric_normal_predictor_base.h"
namespace draco {
// This predictor estimates the normal via the surrounding triangles of the
// given corner. Triangles are weighted according to their area.
template <typename DataTypeT, class TransformT, class MeshDataT>
class MeshPredictionSchemeGeometricNormalPredictorArea
: public MeshPredictionSchemeGeometricNormalPredictorBase<
DataTypeT, TransformT, MeshDataT> {
typedef MeshPredictionSchemeGeometricNormalPredictorBase<
DataTypeT, TransformT, MeshDataT>
Base;
public:
explicit MeshPredictionSchemeGeometricNormalPredictorArea(const MeshDataT &md)
: Base(md) {
this->SetNormalPredictionMode(TRIANGLE_AREA);
};
virtual ~MeshPredictionSchemeGeometricNormalPredictorArea() {}
// Computes predicted octahedral coordinates on a given corner.
void ComputePredictedValue(CornerIndex corner_id,
DataTypeT *prediction) override {
DRACO_DCHECK(this->IsInitialized());
typedef typename MeshDataT::CornerTable CornerTable;
const CornerTable *const corner_table = this->mesh_data_.corner_table();
// Going to compute the predicted normal from the surrounding triangles
// according to the connectivity of the given corner table.
VertexCornersIterator<CornerTable> cit(corner_table, corner_id);
// Position of central vertex does not change in loop.
const VectorD<int64_t, 3> pos_cent = this->GetPositionForCorner(corner_id);
// Computing normals for triangles and adding them up.
VectorD<int64_t, 3> normal;
CornerIndex c_next, c_prev;
while (!cit.End()) {
// Getting corners.
if (this->normal_prediction_mode_ == ONE_TRIANGLE) {
c_next = corner_table->Next(corner_id);
c_prev = corner_table->Previous(corner_id);
} else {
c_next = corner_table->Next(cit.Corner());
c_prev = corner_table->Previous(cit.Corner());
}
const VectorD<int64_t, 3> pos_next = this->GetPositionForCorner(c_next);
const VectorD<int64_t, 3> pos_prev = this->GetPositionForCorner(c_prev);
// Computing delta vectors to next and prev.
const VectorD<int64_t, 3> delta_next = pos_next - pos_cent;
const VectorD<int64_t, 3> delta_prev = pos_prev - pos_cent;
// Computing cross product.
const VectorD<int64_t, 3> cross = CrossProduct(delta_next, delta_prev);
// Prevent signed integer overflows by doing math as unsigned.
auto normal_data = reinterpret_cast<uint64_t *>(normal.data());
auto cross_data = reinterpret_cast<const uint64_t *>(cross.data());
normal_data[0] = normal_data[0] + cross_data[0];
normal_data[1] = normal_data[1] + cross_data[1];
normal_data[2] = normal_data[2] + cross_data[2];
cit.Next();
}
// Convert to int32_t, make sure entries are not too large.
constexpr int64_t upper_bound = 1 << 29;
if (this->normal_prediction_mode_ == ONE_TRIANGLE) {
const int32_t abs_sum = static_cast<int32_t>(normal.AbsSum());
if (abs_sum > upper_bound) {
const int64_t quotient = abs_sum / upper_bound;
normal = normal / quotient;
}
} else {
const int64_t abs_sum = normal.AbsSum();
if (abs_sum > upper_bound) {
const int64_t quotient = abs_sum / upper_bound;
normal = normal / quotient;
}
}
DRACO_DCHECK_LE(normal.AbsSum(), upper_bound);
prediction[0] = static_cast<int32_t>(normal[0]);
prediction[1] = static_cast<int32_t>(normal[1]);
prediction[2] = static_cast<int32_t>(normal[2]);
}
bool SetNormalPredictionMode(NormalPredictionMode mode) override {
if (mode == ONE_TRIANGLE) {
this->normal_prediction_mode_ = mode;
return true;
} else if (mode == TRIANGLE_AREA) {
this->normal_prediction_mode_ = mode;
return true;
}
return false;
}
};
} // namespace draco
#endif // DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_MESH_PREDICTION_SCHEME_GEOMETRIC_NORMAL_PREDICTOR_AREA_H_
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