/*
 * Copyright (c) 2007 Sun Microsystems, Inc. All Rights Reserved.
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 * modification, are permitted provided that the following conditions are
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 * Neither the name of Sun Microsystems, Inc. or the names of
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
 * INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
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package net.java.joglutils.msg.nodes;

import java.util.*;

import net.java.joglutils.msg.actions.*;
import net.java.joglutils.msg.elements.*;
import net.java.joglutils.msg.impl.*;
import net.java.joglutils.msg.math.*;
import net.java.joglutils.msg.misc.*;

/** The abstract base class for all shapes in the scene graph which
    render themselves as a collection of triangles. */

public abstract class TriangleBasedShape extends Shape {
  /** Based on the state in the given Action, calls the specified
      triangle callback for each triangle in the shape. Coordinates
      are specified in the local coordinate system of this shape; the
      caller must transform them into the world coordinate system if
      necessary. */
  public abstract void generateTriangles(Action action,
                                         TriangleCallback cb);

  public void rayPick(final RayPickAction action) {
    // The RayPickAction holds the picking ray in world coordinates.
    // Transform this ray into local coordinates to do intersection testing
    // Fetch the current local-to-world matrix
    Mat4f mat = new Mat4f(ModelMatrixElement.getInstance(action.getState()).getMatrix());
    // Invert it to get the world-to-local matrix
    mat.invert();
    // Transform the RayPickAction's ray by this matrix
    final Line ray = mat.xformLine(action.getComputedRay());

    // Temporaries
    final RayTriangleIntersection rti = new RayTriangleIntersection();
    final Vec3f tuv = new Vec3f();

    // OK, ready to test
    generateTriangles(action, new TriangleCallback() {
        public void triangleCB(int triangleIndex,
                               PrimitiveVertex v0,
                               int i0,
                               PrimitiveVertex v1,
                               int i1,
                               PrimitiveVertex v2,
                               int i2) {
          if (rti.intersectTriangle(ray,
                                    v0.getCoord(),
                                    v1.getCoord(),
                                    v2.getCoord(),
                                    tuv)) {
            // Compute at least the 3D coordinate of the intersection
            // point for now
            // FIXME: need to compute other things such as the texture
            // coordinates
            PickedPoint p = new PickedPoint();
            // Compute weights of three vertices
            float a = 1.0f - tuv.y() - tuv.z();
            float b = tuv.y();
            float c = tuv.z();
            Vec3f loc = v0.getCoord().times(a).plus(v1.getCoord().times(b)).plus(v2.getCoord().times(c));
            p.setCoord(loc);
            p.setPath(action.getPath().copy());
            action.addPickedPoint(p, tuv.x());
          }
        }
      });
  }
}