geomTristrips.cxx

Go to the documentation of this file.

/**
 * 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 geomTristrips.cxx
 * @author drose
 * @date 2005-03-08
 */
 
#include "geomTristrips.h"
#include "geomTriangles.h"
#include "geomVertexRewriter.h"
#include "pStatTimer.h"
#include "bamReader.h"
#include "bamWriter.h"
#include "graphicsStateGuardianBase.h"
#include "geomTristripsAdjacency.h"
 
using std::map;
 
TypeHandle GeomTristrips::_type_handle;
 
/**
 *
 */
GeomTristrips::
GeomTristrips(GeomTristrips::UsageHint usage_hint) :
  GeomPrimitive(usage_hint)
{
}
 
/**
 *
 */
GeomTristrips::
GeomTristrips(const GeomTristrips &copy) :
  GeomPrimitive(copy)
{
}
 
/**
 *
 */
GeomTristrips::
~GeomTristrips() {
}
 
/**
 *
 */
PT(GeomPrimitive) GeomTristrips::
make_copy() const {
  return new GeomTristrips(*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 GeomTristrips::
get_primitive_type() const {
  return PT_polygons;
}
 
/**
 * Returns the set of GeomRendering bits that represent the rendering
 * properties required to properly render this primitive.
 */
int GeomTristrips::
get_geom_rendering() const {
  if (is_indexed()) {
    return GR_triangle_strip | GR_indexed_other;
  } else {
    return GR_triangle_strip;
  }
}
 
/**
 * Adds adjacency information to this primitive.  May return null if this type
 * of geometry does not support adjacency information.
 */
CPT(GeomPrimitive) GeomTristrips::
make_adjacency() const {
  using std::make_pair;
 
  Thread *current_thread = Thread::get_current_thread();
  PT(GeomTristripsAdjacency) adj = new GeomTristripsAdjacency(get_usage_hint());
  CPTA_int ends = get_ends();
 
  GeomPrimitivePipelineReader from(this, current_thread);
  int num_vertices = from.get_num_vertices();
  const int num_unused = 2;
 
  // First, build a map of each triangle's halfedges to its opposing vertices.
  map<std::pair<int, int>, int> edge_map;
 
  int vi = -num_unused;
  int li = 0;
  while (li < (int)ends.size()) {
    // Skip unused vertices between tristrips.
    vi += num_unused;
    int end = ends[li];
    nassertr(vi + 2 <= end, nullptr);
 
    int v0 = from.get_vertex(vi++);
    int v1 = from.get_vertex(vi++);
    int v2 = from.get_vertex(vi);
    edge_map[make_pair(v0, v1)] = v2;
 
    while (true) {
      v2 = from.get_vertex(vi++);
      edge_map[make_pair(v2, v0)] = v1;
 
      if (vi >= end) {
        // Edge at the end of the strip
        edge_map[make_pair(v1, v2)] = v0;
        break;
      }
 
      v0 = v1;
      v1 = v2;
      v2 = from.get_vertex(vi++);
      edge_map[make_pair(v0, v2)] = v1;
 
      if (vi >= end) {
        // Edge at the end of the strip
        edge_map[make_pair(v2, v1)] = v0;
        break;
      }
 
      v0 = v1;
      v1 = v2;
    }
    ++li;
  }
  nassertr(vi == num_vertices, nullptr);
 
  // Now build up the new vertex data.  For each edge, we insert the
  // appropriate connecting vertex.
  vi = -num_unused;
  li = 0;
  while (li < (int)ends.size()) {
    // Skip unused vertices between tristrips.
    vi += num_unused;
    int end = ends[li];
    nassertr(vi + 2 <= end, nullptr);
 
    int v0 = from.get_vertex(vi++);
    int v1 = from.get_vertex(vi++);
    int v2;
    adj->add_vertex(v0);
 
    // Get the third vertex of the triangle adjoining this edge.
    auto it = edge_map.find(make_pair(v1, v0));
    if (it != edge_map.end()) {
      adj->add_vertex(it->second);
    } else {
      // Um, no adjoining triangle?  Just repeat the vertex, I guess.
      adj->add_vertex(v0);
    }
    adj->add_vertex(v1);
 
    while (true) {
      v2 = from.get_vertex(vi++);
      it = edge_map.find(make_pair(v0, v2));
      if (it != edge_map.end()) {
        adj->add_vertex(it->second);
      } else {
        adj->add_vertex(v1);
      }
      adj->add_vertex(v2);
 
      if (vi >= end) {
        // Edge at the end of the strip
        it = edge_map.find(make_pair(v2, v1));
        if (it != edge_map.end()) {
          adj->add_vertex(it->second);
        } else {
          adj->add_vertex(v2);
        }
        break;
      }
 
      v0 = v1;
      v1 = v2;
      v2 = from.get_vertex(vi++);
      it = edge_map.find(make_pair(v2, v0));
      if (it != edge_map.end()) {
        adj->add_vertex(it->second);
      } else {
        adj->add_vertex(v1);
      }
      adj->add_vertex(v2);
 
      if (vi >= end) {
        // Edge at the end of the strip
        it = edge_map.find(make_pair(v1, v2));
        if (it != edge_map.end()) {
          adj->add_vertex(it->second);
        } else {
          adj->add_vertex(v1);
        }
        break;
      }
 
      v0 = v1;
      v1 = v2;
    }
    adj->close_primitive();
    ++li;
  }
  nassertr(vi == num_vertices, nullptr);
 
  return adj;
}
 
/**
 * Returns the minimum number of vertices that must be added before
 * close_primitive() may legally be called.
 */
int GeomTristrips::
get_min_num_vertices_per_primitive() const {
  return 3;
}
 
/**
 * Returns the number of vertices that are added between primitives that
 * aren't, strictly speaking, part of the primitives themselves.  This is
 * used, for instance, to define degenerate triangles to connect otherwise
 * disconnected triangle strips.
 */
int GeomTristrips::
get_num_unused_vertices_per_primitive() const {
  return 2;
}
 
/**
 * Calls the appropriate method on the GSG to draw the primitive.
 */
bool GeomTristrips::
draw(GraphicsStateGuardianBase *gsg, const GeomPrimitivePipelineReader *reader,
     bool force) const {
  return gsg->draw_tristrips(reader, force);
}
 
/**
 * Decomposes a complex primitive type into a simpler primitive type, for
 * instance triangle strips to triangles, and returns a pointer to the new
 * primitive definition.  If the decomposition cannot be performed, this might
 * return the original object.
 *
 * This method is useful for application code that wants to iterate through
 * the set of triangles on the primitive without having to write handlers for
 * each possible kind of primitive type.
 */
CPT(GeomPrimitive) GeomTristrips::
decompose_impl() const {
  PT(GeomTriangles) triangles = new GeomTriangles(get_usage_hint());
  triangles->set_shade_model(get_shade_model());
  CPTA_int ends = get_ends();
 
  int num_vertices = get_num_vertices();
  int num_unused = get_num_unused_vertices_per_primitive();
 
  // We need a slightly different algorithm for SM_flat_first_vertex than for
  // SM_flat_last_vertex, to preserve the key vertex in the right place.  The
  // remaining shade models can use either algorithm.
  if (get_shade_model() == SM_flat_first_vertex) {
    // Preserve the first vertex of each component triangle as the first
    // vertex of each generated triangle.
    int vi = -num_unused;
    int li = 0;
    while (li < (int)ends.size()) {
      // Skip unused vertices between tristrips.
      vi += num_unused;
      int end = ends[li];
      nassertr(vi + 2 <= end, nullptr);
      int v0 = get_vertex(vi);
      ++vi;
      int v1 = get_vertex(vi);
      ++vi;
      bool reversed = false;
      while (vi < end) {
        int v2 = get_vertex(vi);
        ++vi;
        if (reversed) {
          if (v0 != v1 && v0 != v2 && v1 != v2) {
            triangles->add_vertex(v0);
            triangles->add_vertex(v2);
            triangles->add_vertex(v1);
            triangles->close_primitive();
          }
          reversed = false;
        } else {
          if (v0 != v1 && v0 != v2 && v1 != v2) {
            triangles->add_vertex(v0);
            triangles->add_vertex(v1);
            triangles->add_vertex(v2);
            triangles->close_primitive();
          }
          reversed = true;
        }
        v0 = v1;
        v1 = v2;
      }
      ++li;
    }
    nassertr(vi == num_vertices, nullptr);
 
  } else {
    // Preserve the last vertex of each component triangle as the last vertex
    // of each generated triangle.
    int vi = -num_unused;
    int li = 0;
    while (li < (int)ends.size()) {
      // Skip unused vertices between tristrips.
      vi += num_unused;
      int end = ends[li];
      nassertr(vi + 2 <= end, nullptr);
      int v0 = get_vertex(vi);
      ++vi;
      int v1 = get_vertex(vi);
      ++vi;
      bool reversed = false;
      while (vi < end) {
        int v2 = get_vertex(vi);
        if (reversed) {
          if (v0 != v1 && v0 != v2 && v1 != v2) {
            triangles->add_vertex(v1);
            triangles->add_vertex(v0);
            triangles->add_vertex(v2);
            triangles->close_primitive();
          }
          reversed = false;
        } else {
          if (v0 != v1 && v0 != v2 && v1 != v2) {
            triangles->add_vertex(v0);
            triangles->add_vertex(v1);
            triangles->add_vertex(v2);
            triangles->close_primitive();
          }
          reversed = true;
        }
        ++vi;
        v0 = v1;
        v1 = v2;
      }
      ++li;
    }
    nassertr(vi == num_vertices, nullptr);
  }
 
  return triangles;
}
 
/**
 * The virtual implementation of doubleside().
 */
CPT(GeomPrimitive) GeomTristrips::
doubleside_impl() const {
  // TODO: implement this properly as triangle strips, without requiring a
  // decompose operation first.
  return decompose_impl()->doubleside();
}
 
/**
 * The virtual implementation of reverse().
 */
CPT(GeomPrimitive) GeomTristrips::
reverse_impl() const {
  // TODO: implement this properly as triangle strips, without requiring a
  // decompose operation first.
  return decompose_impl()->reverse();
}
 
/**
 * The virtual implementation of do_rotate().
 */
CPT(GeomVertexArrayData) GeomTristrips::
rotate_impl() const {
  // To rotate a triangle strip with an even number of vertices, we just
  // reverse the vertices.  But if we have an odd number of vertices, that
  // doesn't work--in fact, nothing works (without also changing the winding
  // order), so we don't allow an odd number of vertices in a flat-shaded
  // tristrip.
  CPTA_int ends = get_ends();
 
  PT(GeomVertexArrayData) new_vertices = make_index_data();
  new_vertices->set_num_rows(get_num_vertices());
 
  if (is_indexed()) {
    CPT(GeomVertexArrayData) vertices = get_vertices();
    GeomVertexReader from(vertices, 0);
    GeomVertexWriter to(new_vertices, 0);
 
    int begin = 0;
    int last_added = 0;
    CPTA_int::const_iterator ei;
    for (ei = ends.begin(); ei != ends.end(); ++ei) {
      int end = (*ei);
      int num_vertices = end - begin;
 
      if (begin != 0) {
        // Copy in the unused vertices between tristrips.
        to.set_data1i(last_added);
        from.set_row_unsafe(end - 1);
        to.set_data1i(from.get_data1i());
        begin += 2;
      }
 
      // If this assertion is triggered, there was a triangle strip with an
      // odd number of vertices, which is not allowed.
      nassertr((num_vertices & 1) == 0, nullptr);
      for (int vi = end - 1; vi >= begin; --vi) {
        from.set_row_unsafe(vi);
        last_added = from.get_data1i();
        to.set_data1i(last_added);
      }
 
      begin = end;
    }
 
    nassertr(to.is_at_end(), nullptr);
 
  } else {
    // Nonindexed case.
    int first_vertex = get_first_vertex();
    GeomVertexWriter to(new_vertices, 0);
 
    int begin = 0;
    int last_added = 0;
    CPTA_int::const_iterator ei;
    for (ei = ends.begin(); ei != ends.end(); ++ei) {
      int end = (*ei);
      int num_vertices = end - begin;
 
      if (begin != 0) {
        // Copy in the unused vertices between tristrips.
        to.set_data1i(last_added);
        to.set_data1i(end - 1 + first_vertex);
        begin += 2;
      }
 
      // If this assertion is triggered, there was a triangle strip with an
      // odd number of vertices, which is not allowed.
      nassertr((num_vertices & 1) == 0, nullptr);
      for (int vi = end - 1; vi >= begin; --vi) {
        last_added = vi + first_vertex;
        to.set_data1i(last_added);
      }
 
      begin = end;
    }
 
    nassertr(to.is_at_end(), nullptr);
  }
  return new_vertices;
}
 
/**
 * Should be redefined to return true in any primitive that implements
 * append_unused_vertices().
 */
bool GeomTristrips::
requires_unused_vertices() const {
  return true;
}
 
/**
 * Called when a new primitive is begun (other than the first primitive), this
 * should add some degenerate vertices between primitives, if the primitive
 * type requires that.  The second parameter is the first vertex that begins
 * the new primitive.
 */
void GeomTristrips::
append_unused_vertices(GeomVertexArrayData *vertices, int vertex) {
  GeomVertexReader from(vertices, 0);
  from.set_row_unsafe(vertices->get_num_rows() - 1);
  int prev = from.get_data1i();
 
  GeomVertexWriter to(vertices, 0);
  to.set_row_unsafe(vertices->get_num_rows());
 
  to.add_data1i(prev);
  to.add_data1i(vertex);
}
 
/**
 * Tells the BamReader how to create objects of type Geom.
 */
void GeomTristrips::
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 *GeomTristrips::
make_from_bam(const FactoryParams &params) {
  GeomTristrips *object = new GeomTristrips(UH_unspecified);
  DatagramIterator scan;
  BamReader *manager;
 
  parse_params(params, scan, manager);
  object->fillin(scan, manager);
 
  return object;
}