Triangulate.cpp

/**************************************************************************/
/*** END OF HEADER FILE TRIANGULATE.H BEGINNING OF CODE TRIANGULATE.CPP ***/
/**************************************************************************/
#include "stdafx.h"
#include "Triangulate.h"

using namespace Ogre;
using namespace std;

static const float EPSILON=0.0000000001f;

float Triangulate::Area(const std::vector<Vector2> &contour)
{

  size_t N = contour.size();

  float A=0.0f;

  for(size_t p = N - 1, q = 0; q < N; p = q++)
  {
    A+= contour[p].x*contour[q].y - contour[q].x*contour[p].y;
  }
  return A*0.5f;
}

/*
 InsideTriangle decides if a point P is Inside of the triangle
 defined by A, B, C.
*/
bool Triangulate::InsideTriangle(float Ax, float Ay,
                      float Bx, float By,
                      float Cx, float Cy,
                      float Px, float Py)

{
  float ax, ay, bx, by, cx, cy, apx, apy, bpx, bpy, cpx, cpy;
  float cCROSSap, bCROSScp, aCROSSbp;

  ax = Cx - Bx;  ay = Cy - By;
  bx = Ax - Cx;  by = Ay - Cy;
  cx = Bx - Ax;  cy = By - Ay;
  apx= Px - Ax;  apy= Py - Ay;
  bpx= Px - Bx;  bpy= Py - By;
  cpx= Px - Cx;  cpy= Py - Cy;

  aCROSSbp = ax*bpy - ay*bpx;
  cCROSSap = cx*apy - cy*apx;
  bCROSScp = bx*cpy - by*cpx;

  return ((aCROSSbp >= 0.0f) && (bCROSScp >= 0.0f) && (cCROSSap >= 0.0f));
};

bool Triangulate::Snip(const std::vector<Vector2> &contour,int u,int v,int w,int n,int *V)
{
  int p;
  float Ax, Ay, Bx, By, Cx, Cy, Px, Py;

  Ax = contour[V[u]].x;
  Ay = contour[V[u]].y;

  Bx = contour[V[v]].x;
  By = contour[V[v]].y;

  Cx = contour[V[w]].x;
  Cy = contour[V[w]].y;

  if (EPSILON > (((Bx-Ax)*(Cy-Ay)) - ((By-Ay)*(Cx-Ax)))) return false;

  for (p=0;p<n;p++)
  {
    if((p == u) || (p == v) || (p == w)) continue;
    Px = contour[V[p]].x;
    Py = contour[V[p]].y;
    if (InsideTriangle(Ax,Ay,Bx,By,Cx,Cy,Px,Py)) return false;
  }

  return true;
}

bool Triangulate::Process(const std::vector<Vector2> &contour, std::vector<Vector2> &result)
{
  /* allocate and initialize list of Vertices in polygon */

  int n = contour.size();
  if (n < 3) return false;

  int *V = new int[n];

  /* we want a counter-clockwise polygon in V */

  if (0.0f < Area(contour))
    for (int v=0; v<n; v++) V[v] = v;
  else
    for(int v=0; v<n; v++) V[v] = (n-1)-v;

  int nv = n;

  /*  remove nv-2 Vertices, creating 1 triangle every time */
  int count = 2*nv;   /* error detection */

  for(int m=0, v=nv-1; nv>2;)
  {
    /* if we loop, it is probably a non-simple polygon */
    if (0 >= (count--))
    {
	  // ass monkey: giving me meory leaks
	  delete V;

      //** Triangulate: ERROR - probable bad polygon!
      return false;
    }

    /* three consecutive vertices in current polygon, <u,v,w> */
    int u = v  ; if (nv <= u) u = 0;     /* previous */
    v = u+1; if (nv <= v) v = 0;     /* new v    */
    int w = v+1; if (nv <= w) w = 0;     /* next     */

    if (Snip(contour,u,v,w,nv,V))
    {
      int a,b,c,s,t;

      /* true names of the vertices */
      a = V[u]; b = V[v]; c = V[w];

      /* output Triangle */
      result.push_back(contour[a]);
      result.push_back(contour[b]);
      result.push_back(contour[c]);

      m++;

      /* remove v from remaining polygon */
      for(s=v,t=v+1;t<nv;s++,t++) V[s] = V[t]; nv--;

      /* resest error detection counter */
      count = 2*nv;
    }
  }

  delete V;

  return true;
}


//need to be an indexed version
bool Triangulate::Process(const std::vector<Vector2> &contour, std::vector<size_t> &result)
{
  /* allocate and initialize list of Vertices in polygon */

  int n = contour.size();
  if (n < 3) return false;

  int *V = new int[n];

  /* we want a counter-clockwise polygon in V */

  if (0.0f < Area(contour))
    for (int v=0; v<n; v++) V[v] = v;
  else
    for(int v=0; v<n; v++) V[v] = (n-1)-v;

  int nv = n;

  /*  remove nv-2 Vertices, creating 1 triangle every time */
  int count = 2*nv;   /* error detection */

  for(int m=0, v=nv-1; nv>2;)
  {
    /* if we loop, it is probably a non-simple polygon */
    if (0 >= (count--))
    {
	  // ass monkey: giving me meory leaks
	  delete V;

      //** Triangulate: ERROR - probable bad polygon!
      return false;
    }

    /* three consecutive vertices in current polygon, <u,v,w> */
    int u = v  ; if (nv <= u) u = 0;     /* previous */
    v = u+1; if (nv <= v) v = 0;     /* new v    */
    int w = v+1; if (nv <= w) w = 0;     /* next     */

    if (Snip(contour,u,v,w,nv,V))
    {
      int a,b,c,s,t;

      /* true names of the vertices */
      a = V[u]; b = V[v]; c = V[w];

      /* output Triangle */
      result.push_back(c);
      result.push_back(b);
      result.push_back(a);

      m++;

      /* remove v from remaining polygon */
      for(s=v,t=v+1;t<nv;s++,t++) V[s] = V[t]; nv--;

      /* resest error detection counter */
      count = 2*nv;
    }
  }

  delete V;

  return true;
}


//need to be an indexed version
bool Triangulate::Process(const std::vector<Vector2> &contour, std::vector<uint16> &result)
{
	/* allocate and initialize list of Vertices in polygon */

	int n = contour.size();
	if (n < 3) return false;

	int *V = new int[n];

	/* we want a counter-clockwise polygon in V */

	if (0.0f < Area(contour))
		for (int v=0; v<n; v++) V[v] = v;
	else
		for(int v=0; v<n; v++) V[v] = (n-1)-v;

	int nv = n;

	/*  remove nv-2 Vertices, creating 1 triangle every time */
	int count = 2*nv;   /* error detection */

	for(int m=0, v=nv-1; nv>2;)
	{
		/* if we loop, it is probably a non-simple polygon */
		if (0 >= (count--))
		{
			// ass monkey: giving me meory leaks
			delete V;

			//** Triangulate: ERROR - probable bad polygon!
			return false;
		}

		/* three consecutive vertices in current polygon, <u,v,w> */
		int u = v  ; if (nv <= u) u = 0;     /* previous */
		v = u+1; if (nv <= v) v = 0;     /* new v    */
		int w = v+1; if (nv <= w) w = 0;     /* next     */

		if (Snip(contour,u,v,w,nv,V))
		{
			int a,b,c,s,t;

			/* true names of the vertices */
			a = V[u]; b = V[v]; c = V[w];

			/* output Triangle */
			result.push_back(static_cast<Ogre::uint16>(c));
			result.push_back(static_cast<Ogre::uint16>(b));
			result.push_back(static_cast<Ogre::uint16>(a));

			m++;

			/* remove v from remaining polygon */
			for(s=v,t=v+1;t<nv;s++,t++) V[s] = V[t]; nv--;

			/* resest error detection counter */
			count = 2*nv;
		}
	}

	delete V;

	return true;
}





//need to be an indexed version
bool Triangulate::Process(const std::vector<Vector3> &contour, std::vector<size_t> &result)
{
	/* allocate and initialize list of Vertices in polygon */

	int n = contour.size();
	if (n < 3) return false;

	int *V = new int[n];

	/* we want a counter-clockwise polygon in V */

	if (0.0f < Area(contour))
		for (int v=0; v<n; v++) V[v] = v;
	else
		for(int v=0; v<n; v++) V[v] = (n-1)-v;

	int nv = n;

	/*  remove nv-2 Vertices, creating 1 triangle every time */
	int count = 2*nv;   /* error detection */

	for(int m=0, v=nv-1; nv>2;)
	{
		/* if we loop, it is probably a non-simple polygon */
		if (0 >= (count--))
		{
			// ass monkey: giving me meory leaks
			delete V;

			//** Triangulate: ERROR - probable bad polygon!
			return false;
		}

		/* three consecutive vertices in current polygon, <u,v,w> */
		int u = v  ; if (nv <= u) u = 0;     /* previous */
		v = u+1; if (nv <= v) v = 0;     /* new v    */
		int w = v+1; if (nv <= w) w = 0;     /* next     */

		if (Snip(contour,u,v,w,nv,V))
		{
			int a,b,c,s,t;

			/* true names of the vertices */
			a = V[u]; b = V[v]; c = V[w];

			/* output Triangle */
			result.push_back(c);
			result.push_back(b);
			result.push_back(a);

			m++;

			/* remove v from remaining polygon */
			for(s=v,t=v+1;t<nv;s++,t++) V[s] = V[t]; nv--;

			/* resest error detection counter */
			count = 2*nv;
		}
	}

	delete V;

	return true;
}

bool Triangulate::Process(const std::vector<Vector3> &contour, std::vector<Ogre::uint16> &result)
{
	/* allocate and initialize list of Vertices in polygon */

	int n = contour.size();
	if (n < 3) return false;

	int *V = new int[n];

	/* we want a counter-clockwise polygon in V */

	if (0.0f < Area(contour))
		for (int v=0; v<n; v++) V[v] = v;
	else
		for(int v=0; v<n; v++) V[v] = (n-1)-v;

	int nv = n;

	/*  remove nv-2 Vertices, creating 1 triangle every time */
	int count = 2*nv;   /* error detection */

	for(int m=0, v=nv-1; nv>2;)
	{
		/* if we loop, it is probably a non-simple polygon */
		if (0 >= (count--))
		{
			// ass monkey: giving me meory leaks
			delete V;

			//** Triangulate: ERROR - probable bad polygon!
			return false;
		}

		/* three consecutive vertices in current polygon, <u,v,w> */
		int u = v  ; if (nv <= u) u = 0;     /* previous */
		v = u+1; if (nv <= v) v = 0;     /* new v    */
		int w = v+1; if (nv <= w) w = 0;     /* next     */

		if (Snip(contour,u,v,w,nv,V))
		{
			int a,b,c,s,t;

			/* true names of the vertices */
			a = V[u]; b = V[v]; c = V[w];

			/* output Triangle */
			result.push_back(static_cast<Ogre::uint16>(c));
			result.push_back(static_cast<Ogre::uint16>(b));
			result.push_back(static_cast<Ogre::uint16>(a));

			m++;

			/* remove v from remaining polygon */
			for(s=v,t=v+1;t<nv;s++,t++) V[s] = V[t]; nv--;

			/* resest error detection counter */
			count = 2*nv;
		}
	}

	delete V;

	return true;
}

float Triangulate::Area(const std::vector<Vector3> &contour)
{

	size_t N = contour.size();

	float A=0.0f;

	for(size_t p = N - 1, q = 0; q < N; p = q++)
	{
		A+= contour[p].x*contour[q].z - contour[q].x*contour[p].z;
	}
	return A*0.5f;
}

bool Triangulate::Snip(const std::vector<Vector3> &contour,int u,int v,int w,int n,int *V)
{
	int p;
	float Ax, Ay, Bx, By, Cx, Cy, Px, Py;

	Ax = contour[V[u]].x;
	Ay = contour[V[u]].z;

	Bx = contour[V[v]].x;
	By = contour[V[v]].z;

	Cx = contour[V[w]].x;
	Cy = contour[V[w]].z;

	if (EPSILON > (((Bx-Ax)*(Cy-Ay)) - ((By-Ay)*(Cx-Ax)))) return false;

	for (p=0;p<n;p++)
	{
		if((p == u) || (p == v) || (p == w)) continue;
		Px = contour[V[p]].x;
		Py = contour[V[p]].z;
		if (InsideTriangle(Ax,Ay,Bx,By,Cx,Cy,Px,Py)) return false;
	}

	return true;
}