mesh_misc_functions.h

// 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.
//
// This file contains misc functions that are needed by several mesh related
// algorithms.

#ifndef DRACO_MESH_MESH_MISC_FUNCTIONS_H_
#define DRACO_MESH_MESH_MISC_FUNCTIONS_H_

#include "draco/mesh/corner_table.h"
#include "draco/mesh/mesh.h"

// The file contains functions that use both Mesh and CornerTable as inputs.
namespace draco {

// Creates a CornerTable from the position attribute of |mesh|. Returns nullptr
// on error.
std::unique_ptr<CornerTable> CreateCornerTableFromPositionAttribute(
    const Mesh *mesh);

// Creates a CornerTable from the first named attribute of |mesh| with a given
// type. Returns nullptr on error.
std::unique_ptr<CornerTable> CreateCornerTableFromAttribute(
    const Mesh *mesh, GeometryAttribute::Type type);

// Creates a CornerTable from all attributes of |mesh|. Boundaries are
// automatically introduced on all attribute seams. Returns nullptr on error.
std::unique_ptr<CornerTable> CreateCornerTableFromAllAttributes(
    const Mesh *mesh);

// Returns true when the given corner lies opposite to an attribute seam.
inline bool IsCornerOppositeToAttributeSeam(CornerIndex ci,
                                            const PointAttribute &att,
                                            const Mesh &mesh,
                                            const CornerTable &ct) {
  const CornerIndex opp_ci = ct.Opposite(ci);
  if (opp_ci == kInvalidCornerIndex) {
    return false;  // No opposite corner == no attribute seam.
  }
  // Compare attribute value indices on both ends of the opposite edge.
  CornerIndex c0 = ct.Next(ci);
  CornerIndex c1 = ct.Previous(opp_ci);
  if (att.mapped_index(mesh.CornerToPointId(c0)) !=
      att.mapped_index(mesh.CornerToPointId(c1))) {
    return true;
  }
  c0 = ct.Previous(ci);
  c1 = ct.Next(opp_ci);
  if (att.mapped_index(mesh.CornerToPointId(c0)) !=
      att.mapped_index(mesh.CornerToPointId(c1))) {
    return true;
  }
  return false;
}

// Interpolates an attribute value on a face using given barycentric
// coordinates. InterpolatedVectorT should be a VectorD that corresponds to the
// values stored in the attribute.
template <typename InterpolatedVectorT>
InterpolatedVectorT ComputeInterpolatedAttributeValueOnMeshFace(
    const Mesh &mesh, const PointAttribute &attribute, FaceIndex fi,
    const std::array<float, 3> &barycentric_coord) {
  const Mesh::Face &face = mesh.face(fi);
  // Get values for all three corners of the face.
  InterpolatedVectorT val[3];
  for (int c = 0; c < 3; ++c) {
    attribute.GetMappedValue(face[c], &(val[c][0]));
  }
  // Return an interpolated value.
  InterpolatedVectorT res;
  for (int d = 0; d < InterpolatedVectorT::dimension; ++d) {
    const float interpolated_component = barycentric_coord[0] * val[0][d] +
                                         barycentric_coord[1] * val[1][d] +
                                         barycentric_coord[2] * val[2][d];
    if (std::is_integral<typename InterpolatedVectorT::Scalar>::value) {
      res[d] = std::floor(interpolated_component + 0.5f);
    } else {
      res[d] = interpolated_component;
    }
  }
  return res;
}

}  // namespace draco

#endif  // DRACO_MESH_MESH_MISC_FUNCTIONS_H_