geomTrifans.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 geomTrifans.cxx
 * @author drose
 * @date 2005-03-08
 */

#include "geomTrifans.h"
#include "geomTriangles.h"
#include "geomVertexRewriter.h"
#include "bamReader.h"
#include "bamWriter.h"
#include "graphicsStateGuardianBase.h"

TypeHandle GeomTrifans::_type_handle;

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

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

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

/**
 *
 */
PT(GeomPrimitive) GeomTrifans::
make_copy() const {
  return new GeomTrifans(*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 GeomTrifans::
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 GeomTrifans::
get_geom_rendering() const {
  if (is_indexed()) {
    return GR_triangle_fan | GR_indexed_other;
  } else {
    return GR_triangle_fan;
  }
}

/**
 * Calls the appropriate method on the GSG to draw the primitive.
 */
bool GeomTrifans::
draw(GraphicsStateGuardianBase *gsg, const GeomPrimitivePipelineReader *reader,
     bool force) const {
  return gsg->draw_trifans(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) GeomTrifans::
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 vi = 0;
  int li = 0;
  while (li < (int)ends.size()) {
    int end = ends[li];
    nassertr(vi + 2 <= end, triangles);
    int v0 = get_vertex(vi);
    ++vi;
    int v1 = get_vertex(vi);
    ++vi;
    while (vi < end) {
      int v2 = get_vertex(vi);
      ++vi;
      triangles->add_vertex(v0);
      triangles->add_vertex(v1);
      triangles->add_vertex(v2);
      v1 = v2;
      triangles->close_primitive();
    }
    ++li;
  }

  nassertr(vi == num_vertices, nullptr);

  return triangles;
}

/**
 * The virtual implementation of do_rotate().
 */
CPT(GeomVertexArrayData) GeomTrifans::
rotate_impl() const {
  // Actually, we can't rotate fans without chaging the winding order.  It's
  // an error to define a flat shade model for a GeomTrifan.
  nassert_raise("GeomTrifans cannot have flat shading model");
  return nullptr;
}

/**
 * Tells the BamReader how to create objects of type Geom.
 */
void GeomTrifans::
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 *GeomTrifans::
make_from_bam(const FactoryParams &params) {
  GeomTrifans *object = new GeomTrifans(UH_unspecified);
  DatagramIterator scan;
  BamReader *manager;

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

  return object;
}