geomTriangles.cxx

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/**
 * PANDA 3D SOFTWARE
 * Copyright (c) Carnegie Mellon University.  All rights reserved.
 *
 * All use of this software is subject to the terms of the revised BSD
 * license.  You should have received a copy of this license along
 * with this source code in a file named "LICENSE."
 *
 * @file geomTriangles.cxx
 * @author drose
 * @date 2005-03-06
 */

#include "geomTriangles.h"
#include "geomVertexRewriter.h"
#include "pStatTimer.h"
#include "bamReader.h"
#include "bamWriter.h"
#include "graphicsStateGuardianBase.h"
#include "geomTrianglesAdjacency.h"

using std::map;

TypeHandle GeomTriangles::_type_handle;

/**
 *
 */
GeomTriangles::
GeomTriangles(GeomTriangles::UsageHint usage_hint) :
  GeomPrimitive(usage_hint)
{
}

/**
 *
 */
GeomTriangles::
GeomTriangles(const GeomTriangles &copy) :
  GeomPrimitive(copy)
{
}

/**
 *
 */
GeomTriangles::
~GeomTriangles() {
}

/**
 *
 */
PT(GeomPrimitive) GeomTriangles::
make_copy() const {
  return new GeomTriangles(*this);
}

/**
 * Returns the fundamental rendering type of this primitive: whether it is
 * points, lines, or polygons.
 *
 * This is used to set up the appropriate antialiasing settings when
 * AntialiasAttrib::M_auto is in effect; it also implies the type of primitive
 * that will be produced when decompose() is called.
 */
GeomPrimitive::PrimitiveType GeomTriangles::
get_primitive_type() const {
  return PT_polygons;
}

/**
 * Adds adjacency information to this primitive.  May return null if this type
 * of geometry does not support adjacency information.
 */
CPT(GeomPrimitive) GeomTriangles::
make_adjacency() const {
  using std::make_pair;

  Thread *current_thread = Thread::get_current_thread();
  PT(GeomTrianglesAdjacency) adj = new GeomTrianglesAdjacency(get_usage_hint());

  GeomPrimitivePipelineReader from(this, current_thread);
  int num_vertices = from.get_num_vertices();

  PT(GeomVertexArrayData) new_vertices = adj->make_index_data();
  new_vertices->set_num_rows(num_vertices * 2);

  // First, build a map of each triangle's halfedges to its opposing vertices.
  map<std::pair<int, int>, int> edge_map;
  for (int i = 0; i < num_vertices; i += 3) {
    int v0 = from.get_vertex(i);
    int v1 = from.get_vertex(i + 1);
    int v2 = from.get_vertex(i + 2);
    edge_map[make_pair(v0, v1)] = v2;
    edge_map[make_pair(v1, v2)] = v0;
    edge_map[make_pair(v2, v0)] = v1;
  }

  // Now build up the new vertex data.  For each edge, we insert the
  // appropriate connecting vertex.
  {
    GeomVertexWriter to(new_vertices, 0);
    for (int i = 0; i < num_vertices; i += 3) {
      int v0 = from.get_vertex(i);
      int v1 = from.get_vertex(i + 1);
      int v2 = from.get_vertex(i + 2);

      // Get the third vertex of the triangle adjoining this edge.
      to.set_data1(v0);
      auto it = edge_map.find(make_pair(v1, v0));
      if (it != edge_map.end()) {
        to.set_data1i(it->second);
      } else {
        // Um, no adjoining triangle?  Just repeat the vertex, I guess.
        to.set_data1i(v0);
      }

      // Do the same for the other two edges.
      to.set_data1(v1);
      it = edge_map.find(make_pair(v2, v1));
      if (it != edge_map.end()) {
        to.set_data1i(it->second);
      } else {
        to.set_data1i(v1);
      }

      to.set_data1(v2);
      it = edge_map.find(make_pair(v0, v2));
      if (it != edge_map.end()) {
        to.set_data1i(it->second);
      } else {
        to.set_data1i(v2);
      }
    }

    nassertr(to.is_at_end(), nullptr);
  }

  adj->set_vertices(std::move(new_vertices));
  return adj;
}

/**
 * If the primitive type is a simple type in which all primitives have the
 * same number of vertices, like triangles, returns the number of vertices per
 * primitive.  If the primitive type is a more complex type in which different
 * primitives might have different numbers of vertices, for instance a
 * triangle strip, returns 0.
 */
int GeomTriangles::
get_num_vertices_per_primitive() const {
  return 3;
}

/**
 * Calls the appropriate method on the GSG to draw the primitive.
 */
bool GeomTriangles::
draw(GraphicsStateGuardianBase *gsg, const GeomPrimitivePipelineReader *reader,
     bool force) const {
  return gsg->draw_triangles(reader, force);
}

/**
 * The virtual implementation of doubleside().
 */
CPT(GeomPrimitive) GeomTriangles::
doubleside_impl() const {
  Thread *current_thread = Thread::get_current_thread();
  PT(GeomTriangles) reversed = new GeomTriangles(*this);

  GeomPrimitivePipelineReader from(this, current_thread);

  // This is like reverse(), except we don't clear the vertices first.  That
  // way we double the vertices up.

  // First, rotate the original copy, if necessary, so the flat-firstflat-last
  // nature of the vertices is consistent throughout the primitive.
  bool needs_rotate = false;
  switch (from.get_shade_model()) {
  case SM_flat_first_vertex:
  case SM_flat_last_vertex:
    reversed = (GeomTriangles *)DCAST(GeomTriangles, reversed->rotate());
    needs_rotate = true;

  default:
    break;
  }

  // Now append all the new vertices, in reverse order.
  for (int i = from.get_num_vertices() - 1; i >= 0; --i) {
    reversed->add_vertex(from.get_vertex(i));
  }

  // Finally, re-rotate the whole thing to get back to the original shade
  // model.
  if (needs_rotate) {
    reversed = (GeomTriangles *)DCAST(GeomTriangles, reversed->rotate());
  }

  return reversed;
}

/**
 * The virtual implementation of reverse().
 */
CPT(GeomPrimitive) GeomTriangles::
reverse_impl() const {
  Thread *current_thread = Thread::get_current_thread();
  PT(GeomTriangles) reversed = new GeomTriangles(*this);

  GeomPrimitivePipelineReader from(this, current_thread);
  reversed->clear_vertices();

  for (int i = from.get_num_vertices() - 1; i >= 0; --i) {
    reversed->add_vertex(from.get_vertex(i));
  }

  switch (from.get_shade_model()) {
  case SM_flat_first_vertex:
    reversed->set_shade_model(SM_flat_last_vertex);
    reversed = (GeomTriangles *)DCAST(GeomTriangles, reversed->rotate());
    break;

  case SM_flat_last_vertex:
    reversed->set_shade_model(SM_flat_first_vertex);
    reversed = (GeomTriangles *)DCAST(GeomTriangles, reversed->rotate());
    break;

  default:
    break;
  }

  return reversed;
}

/**
 * The virtual implementation of rotate().
 */
CPT(GeomVertexArrayData) GeomTriangles::
rotate_impl() const {
  // To rotate triangles, we just move one vertex from the front to the back,
  // or vice-versa; but we have to know what direction we're going.
  ShadeModel shade_model = get_shade_model();
  int num_vertices = get_num_vertices();

  PT(GeomVertexArrayData) new_vertices = make_index_data();
  new_vertices->set_num_rows(num_vertices);

  if (is_indexed()) {
    CPT(GeomVertexArrayData) vertices = get_vertices();
    GeomVertexReader from(vertices, 0);
    GeomVertexWriter to(new_vertices, 0);

    switch (shade_model) {
    case SM_flat_first_vertex:
      // Move the first vertex to the end.
      {
        for (int begin = 0; begin < num_vertices; begin += 3) {
          from.set_row_unsafe(begin + 1);
          to.set_data1i(from.get_data1i());
          to.set_data1i(from.get_data1i());
          from.set_row_unsafe(begin);
          to.set_data1i(from.get_data1i());
        }
      }
      break;

    case SM_flat_last_vertex:
      // Move the last vertex to the front.
      {
        for (int begin = 0; begin < num_vertices; begin += 3) {
          from.set_row_unsafe(begin + 2);
          to.set_data1i(from.get_data1i());
          from.set_row_unsafe(begin);
          to.set_data1i(from.get_data1i());
          to.set_data1i(from.get_data1i());
        }
      }
      break;

    default:
      // This shouldn't get called with any other shade model.
      nassertr(false, vertices);
    }

    nassertr(to.is_at_end(), nullptr);

  } else {
    // Nonindexed case.
    int first_vertex = get_first_vertex();
    GeomVertexWriter to(new_vertices, 0);

    switch (shade_model) {
    case SM_flat_first_vertex:
      // Move the first vertex to the end.
      {
        for (int begin = 0; begin < num_vertices; begin += 3) {
          to.set_data1i(begin + 1 + first_vertex);
          to.set_data1i(begin + 2 + first_vertex);
          to.set_data1i(begin + first_vertex);
        }
      }
      break;

    case SM_flat_last_vertex:
      // Move the last vertex to the front.
      {
        for (int begin = 0; begin < num_vertices; begin += 3) {
          to.set_data1i(begin + 2 + first_vertex);
          to.set_data1i(begin + first_vertex);
          to.set_data1i(begin + 1 + first_vertex);
        }
      }
      break;

    default:
      // This shouldn't get called with any other shade model.
      nassertr(false, nullptr);
    }

    nassertr(to.is_at_end(), nullptr);
  }

  return new_vertices;
}

/**
 * Tells the BamReader how to create objects of type Geom.
 */
void GeomTriangles::
register_with_read_factory() {
  BamReader::get_factory()->register_factory(get_class_type(), make_from_bam);
}

/**
 * This function is called by the BamReader's factory when a new object of
 * type Geom is encountered in the Bam file.  It should create the Geom and
 * extract its information from the file.
 */
TypedWritable *GeomTriangles::
make_from_bam(const FactoryParams &params) {
  GeomTriangles *object = new GeomTriangles(UH_unspecified);
  DatagramIterator scan;
  BamReader *manager;

  parse_params(params, scan, manager);
  object->fillin(scan, manager);

  return object;
}