GU/GU_TriIntersect.h

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/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * Produced by:
 *      David Pritchard
 *      Side Effects Software Inc
 *      123 Front Street West, Suite 1401
 *      Toronto, Ontario
 *      Canada   M5J 2M2
 *      416-504-9876
 *
 * NAME:        GU_TriIntersect.h ( GU Library, C++)
 *
 * COMMENTS: This is a simple callback-style class for finding the contact
 *           points of two static triangles. Clients should override the pure
 *           virtual callback functions to respond to contacts.
 *
 *           The intersection detection assumes that the triangles are
 *           "just touching" and not interpenetrating. In that situation,
 *           contacts can be divided into two types:
 *           - edge/edge collisions, where two triangle edges are touching
 *           - vertex/face collisions, where a corner of one triangle is
 *           touching the other face.
 *
 *           There is some support for interpenetrating cases, via the
 *           face/face collision callback. It's hard to get any useful
 *           information for collision resolution (e.g. normal direction to
 *           resolve collision) when this happens.
 *
 *           This class was originally part of GU_OldOBBTree (formerly
 *           GU_OBBTree). There is some similar code in the SIM libraries,
 *           targetted more at moving triangles.
 */

#ifndef __GU_TriIntersect_h__
#define __GU_TriIntersect_h__

#include "GU_API.h"

#include <UT/UT_Vector3.h>
class bvTriangle;

class GU_API GU_TriIntersect
{
public:
                 GU_TriIntersect();
    virtual     ~GU_TriIntersect();

    // Returns true if an intersection was found.
    bool         intersect(const bvTriangle tris[2], bool cantContact,
                           float tol);

protected:
    // Arguments:
    // - hitpt: intersection of two edges
    // - ea: first edge
    // - eb: second edge
    // - va0,va1: indices of vertices in triangle 0 that form edge
    // - vb0,vb1: indices of vertices in triangle 1 that form edge
    virtual void edgeEdgeCallback(const UT_Vector3 &hitpt,
                                 const UT_Vector3 &normal,
                                 const UT_Vector3 &ea,
                                 const UT_Vector3 &eb,
                                 int va0, int va1, int vb0, int vb1) = 0;

    // - face: which of the two input triangles is the "face" involved in
    // the contact.
    // - vid: id of vertex within triangle
    virtual void vertexFaceCallback(const UT_Vector3 &hitpt,
                                    const UT_Vector3 &normal,
                                    bool isJustTouching,
                                    int face, int vid) = 0;

    // The intersection is every point between hitpt1 and hitpt2. The
    // normals are just the normals of the two faces.
    virtual void faceFaceCallback(const UT_Vector3 &hitpt1,
                                  const UT_Vector3 &hitpt2,
                                  const UT_Vector3 &normal1,
                                  const UT_Vector3 &normal2) = 0;

private:
    // Disallowed.
    GU_TriIntersect(const GU_TriIntersect &);
    GU_TriIntersect &operator=(const GU_TriIntersect &);

    void         intersectEdges(const bvTriangle *t, int i0, int i1,
                                int &hits, float tol);
    void         intersectPoints(const bvTriangle *t,
                                 int &hits, float tol, bool cantContact);
    static void  eliminateLargestComponent(const UT_Vector3 &v, int &i0,
                                           int &i1, int &i2);
    static void  getOddPoints(const float tPS[2][3], int *odd, int *cvt,
                              int *nvt, float tol);
    void         intersectEdgesWithLine(const bvTriangle *t, float *tPC,
                                        float tPS[2][3], int &hits, float tol,
                                        bool cantContact);
};

#endif

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