// * This file is part of the COLOBOT source code
// * Copyright (C) 2001-2008, Daniel ROUX & EPSITEC SA, www.epsitec.ch
// *
// * This program is free software: you can redistribute it and/or modify
// * it under the terms of the GNU General Public License as published by
// * the Free Software Foundation, either version 3 of the License, or
// * (at your option) any later version.
// *
// * This program is distributed in the hope that it will be useful,
// * but WITHOUT ANY WARRANTY; without even the implied warranty of
// * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// * GNU General Public License for more details.
// *
// * You should have received a copy of the GNU General Public License
// * along with this program. If not, see  http://www.gnu.org/licenses/.

// math3d.cpp

#define STRICT
#define D3D_OVERLOADS

#include <math.h>
#include <stdio.h>
#include <d3d.h>

#include "struct.h"
#include "d3dengine.h"
#include "d3dmath.h"
#include "d3dutil.h"
#include "math3d.h"



// Returns TRUE if two numbers are nearly equal.

BOOL IsEqual(float a, float b)
{
	return Abs(a-b) < CHOUIA;
}


// Returns the minimum value.

float Min(float a, float b)
{
	if ( a <= b )  return a;
	else           return b;
}

float Min(float a, float b, float c)
{
	return Min( Min(a,b), c );
}

float Min(float a, float b, float c, float d)
{
	return Min( Min(a,b), Min(c,d) );
}

float Min(float a, float b, float c, float d, float e)
{
	return Min( Min(a,b), Min(c,d), e );
}


// Returns the maximum value.

float Max(float a, float b)
{
	if ( a >= b )  return a;
	else           return b;
}

float Max(float a, float b, float c)
{
	return Max( Max(a,b), c );
}

float Max(float a, float b, float c, float d)
{
	return Max( Max(a,b), Max(c,d) );
}

float Max(float a, float b, float c, float d, float e)
{
	return Max( Max(a,b), Max(c,d), e );
}


// Returns the normalized value (0 .. 1).

float Norm(float a)
{
	if ( a < 0.0f )  return 0.0f;
	if ( a > 1.0f )  return 1.0f;
	return a;
}


// Returns the absolute value of a number.

float Abs(float a)
{
	return (float)fabs(a);
}


// Swaps two integers.

void Swap(int &a, int &b)
{
	int		c;

	c = a;
	a = b;
	b = c;
}

// Swaps two real numbers.

void Swap(float &a, float &b)
{
	float	c;

	c = a;
	a = b;
	b = c;
}

// Permutes two points.

void Swap(FPOINT &a, FPOINT &b)
{
	FPOINT	c;

	c = a;
	a = b;
	b = c;
}

// Returns the modulo of a floating point number.
//	Mod(8.1, 4) = 0.1
//	Mod(n, 1) = fractional part of n

float Mod(float a, float m)
{
	return a - ((int)(a/m))*m;
}

// Returns a normalized angle, that is in other words between 0 and 2 * PI.

float NormAngle(float angle)
{
	angle = Mod(angle, PI*2.0f);
	if ( angle < 0.0f )
	{
		return PI*2.0f + angle;
	}
	else
	{
		return angle;
	}
}

// Test if a angle is between two terminals.

BOOL TestAngle(float angle, float min, float max)
{
	angle = NormAngle(angle);
	min   = NormAngle(min);
	max   = NormAngle(max);

	if ( min > max )
	{
		return ( angle <= max || angle >= min );
	}
	else
	{
		return ( angle >= min && angle <= max );
	}
}


// Calculates the angle to rotate the angle a to the angle g.
// A positive angle is counterclockwise (CCW).

float Direction(float a, float g)
{
	a = NormAngle(a);
	g = NormAngle(g);

	if ( a < g )
	{
		if ( a+PI*2.0f-g < g-a )  a += PI*2.0f;
	}
	else
	{
		if ( g+PI*2.0f-a < a-g )  g += PI*2.0f;
	}
	return (g-a);
}


// Rotates a point around a center.
// The angle is in radians.
// A positive angle is counterclockwise (CCW).

FPOINT RotatePoint(FPOINT center, float angle, FPOINT p)
{
	FPOINT	a, b;

	a.x = p.x-center.x;
	a.y = p.y-center.y;

	b.x = a.x*cosf(angle) - a.y*sinf(angle);
	b.y = a.x*sinf(angle) + a.y*cosf(angle);

	b.x += center.x;
	b.y += center.y;
	return b;
}

// Rotates a point around the origin.
// The angle is in radians.
// A positive angle is counterclockwise (CCW).

FPOINT RotatePoint(float angle, FPOINT p)
{
	FPOINT	a;

	a.x = p.x*cosf(angle) - p.y*sinf(angle);
	a.y = p.x*sinf(angle) + p.y*cosf(angle);

	return a;
}

// Rotates a vector (dist, 0).
// The angle is in radians.
// A positive angle is counterclockwise (CCW).

FPOINT RotatePoint(float angle, float dist)
{
	FPOINT	a;

	a.x = dist*cosf(angle);
	a.y = dist*sinf(angle);

	return a;
}

// Calculates the angle of a right triangle.
// The angle is counterclockwise (CCW), between 0 and 2 * PI.
// For an angle clockwise (CW), just go ahead.
//
//      ^
//      |
//    y o----o
//      |  / |
//      |/)a |
//  ----o----o-->
//      |    x 
//      |

float RotateAngle(float x, float y)
{
#if 1
	if ( x == 0.0f && y == 0.0f )  return 0.0f;

	if ( x >= 0.0f )
	{
		if ( y >= 0.0f )
		{
			if ( x > y )  return           atanf(y/x);
			else          return PI*0.5f - atanf(x/y);
		}
		else
		{
			if ( x > -y )  return PI*2.0f + atanf(y/x);
			else           return PI*1.5f - atanf(x/y);
		}
	}
	else
	{
		if ( y >= 0.0f )
		{
			if ( -x > y )  return PI*1.0f + atanf(y/x);
			else           return PI*0.5f - atanf(x/y);
		}
		else
		{
			if ( -x > -y )  return PI*1.0f + atanf(y/x);
			else            return PI*1.5f - atanf(x/y);
		}
	}
#else
	float	angle;

	if ( x == 0.0f )
	{
		if ( y > 0.0f )
		{
			return 90.0f*PI/180.0f;
		}
		else
		{
			return 270.0f*PI/180.0f;
		}
	}
	else
	{
		angle = atanf(y/x);
		if ( x < 0.0f )
		{
			angle += PI;
		}
		return angle;
	}
#endif
}

// Calculates the angle between two points and one center.
// The angle is in radians.
// A positive angle is counterclockwise (CCW).

float RotateAngle(FPOINT center, FPOINT p1, FPOINT p2)
{
	float	a1, a2, a;

	if ( p1.x == center.x &&
		 p1.y == center.y )  return 0;

	if ( p2.x == center.x &&
		 p2.y == center.y )  return 0;

	a1 = asinf((p1.y-center.y)/Length(p1,center));
	a2 = asinf((p2.y-center.y)/Length(p2,center));

	if ( p1.x < center.x )  a1 = PI-a1;
	if ( p2.x < center.x )  a2 = PI-a2;

	a = a2-a1;
	if ( a < 0 )  a += PI*2;
	return a;
}

// Returns py up on the line ab.

float MidPoint(FPOINT a, FPOINT b, float px)
{
	if ( Abs(a.x-b.x) < CHOUIA )
	{
		if ( a.y < b.y )  return  BEAUCOUP;
		else              return -BEAUCOUP;
	}
	return (b.y-a.y)*(px-a.x)/(b.x-a.x)+a.y;
}

// Advance "dist" along the segment p1-p2.

D3DVECTOR SegmentDist(const D3DVECTOR &p1, const D3DVECTOR &p2, float dist)
{
	return p1+Normalize(p2-p1)*dist;
}

// Check if a point is inside a triangle.

BOOL IsInsideTriangle(FPOINT a, FPOINT b, FPOINT c, FPOINT p)
{
	float	n, m;

	if ( p.x < a.x && p.x < b.x && p.x < c.x )  return FALSE;
	if ( p.x > a.x && p.x > b.x && p.x > c.x )  return FALSE;
	if ( p.y < a.y && p.y < b.y && p.y < c.y )  return FALSE;
	if ( p.y > a.y && p.y > b.y && p.y > c.y )  return FALSE;

	if ( a.x > b.x )  Swap(a,b);
	if ( a.x > c.x )  Swap(a,c);
	if ( c.x < a.x )  Swap(c,a);
	if ( c.x < b.x )  Swap(c,b);

	n = MidPoint(a, b, p.x);
	m = MidPoint(a, c, p.x);
	if ( (n>p.y||p.y>m) && (n<p.y||p.y<m) )  return FALSE;

	n = MidPoint(c, b, p.x);
	m = MidPoint(c, a, p.x);
	if ( (n>p.y||p.y>m) && (n<p.y||p.y<m) )  return FALSE;

	return TRUE;
}

// Calculates the intersection "i" right "of" the plan "abc".

BOOL Intersect(D3DVECTOR a, D3DVECTOR b, D3DVECTOR c,
			   D3DVECTOR d, D3DVECTOR e, D3DVECTOR &i)
{
	float	d1, d2;

	d1 = (d.x-a.x)*((b.y-a.y)*(c.z-a.z)-(c.y-a.y)*(b.z-a.z)) -
		 (d.y-a.y)*((b.x-a.x)*(c.z-a.z)-(c.x-a.x)*(b.z-a.z)) +
		 (d.z-a.z)*((b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y));

	d2 = (d.x-e.x)*((b.y-a.y)*(c.z-a.z)-(c.y-a.y)*(b.z-a.z)) -
		 (d.y-e.y)*((b.x-a.x)*(c.z-a.z)-(c.x-a.x)*(b.z-a.z)) +
		 (d.z-e.z)*((b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y));

	if ( d2 == 0 )  return FALSE;

	i.x = d.x + d1/d2*(e.x-d.x);
	i.y = d.y + d1/d2*(e.y-d.y);
	i.z = d.z + d1/d2*(e.z-d.z);
	return TRUE;
}

// Calculates the intersection of the straight line passing through p (x, z)
// parallel to the y axis, with the plane abc. Returns p.y.

BOOL IntersectY(D3DVECTOR a, D3DVECTOR b, D3DVECTOR c, D3DVECTOR &p)
{
#if 0
	D3DVECTOR	d,e,i;

	d.x = p.x;
	d.y = 0.0f;
	d.z = p.z;
	e.x = p.x;
	e.y = 1.0f;
	e.z = p.z;
	if ( !Intersect(a,b,c,d,e,i) )  return FALSE;
	p.y = i.y;
	return TRUE;
#else
	float	d, d1, d2;

	d  = (b.x-a.x)*(c.z-a.z) - (c.x-a.x)*(b.z-a.z);
	d1 = (p.x-a.x)*(c.z-a.z) - (c.x-a.x)*(p.z-a.z);
	d2 = (b.x-a.x)*(p.z-a.z) - (p.x-a.x)*(b.z-a.z);

	if ( d == 0.0f )  return FALSE;

	p.y = a.y + d1/d*(b.y-a.y) + d2/d*(c.y-a.y);
	return TRUE;
#endif
}


// Rotates a point around a center in the plan.
// The angle is in radians.
// A positive angle is counterclockwise (CCW).

void RotatePoint(float cx, float cy, float angle, float &px, float &py)
{
	float	ax, ay;

	px -= cx;
	py -= cy;

	ax = px*cosf(angle) - py*sinf(angle);
	ay = px*sinf(angle) + py*cosf(angle);

	px = cx+ax;
	py = cy+ay;
}

// Rotates a point around a center in space.
// The angle is in radians.
// A positive angle is counterclockwise (CCW).

void RotatePoint(D3DVECTOR center, float angleH, float angleV, D3DVECTOR &p)
{
	D3DVECTOR	a, b;

	p.x -= center.x;
	p.y -= center.y;
	p.z -= center.z;

	b.x = p.x*cosf(angleH) - p.z*sinf(angleH);
	b.y = p.z*sinf(angleV) + p.y*cosf(angleV);
	b.z = p.x*sinf(angleH) + p.z*cosf(angleH);

	p.x = center.x+b.x;
	p.y = center.y+b.y;
	p.z = center.z+b.z;
}

// Rotates a point around a center in space.
// The angle is in radians.
// A positive angle is counterclockwise (CCW).

void RotatePoint2(D3DVECTOR center, float angleH, float angleV, D3DVECTOR &p)
{
	D3DVECTOR	a, b;

	p.x -= center.x;
	p.y -= center.y;
	p.z -= center.z;

	a.x = p.x*cosf(angleH) - p.z*sinf(angleH);
	a.y = p.y;
	a.z = p.x*sinf(angleH) + p.z*cosf(angleH);

	b.x = a.x;
	b.y = a.z*sinf(angleV) + a.y*cosf(angleV);
	b.z = a.z*cosf(angleV) - a.y*sinf(angleV);

	p.x = center.x+b.x;
	p.y = center.y+b.y;
	p.z = center.z+b.z;
}

// Calculation point of view to look at a center
// two angles and a distance.

D3DVECTOR RotateView(D3DVECTOR center, float angleH, float angleV, float dist)
{
	D3DMATRIX	mat1, mat2, mat;
	D3DVECTOR	eye;

	D3DUtil_SetRotateZMatrix(mat1, -angleV);
	D3DUtil_SetRotateYMatrix(mat2, -angleH);
	D3DMath_MatrixMultiply(mat, mat1, mat2);

	eye.x = 0.0f+dist;
	eye.y = 0.0f;
	eye.z = 0.0f;
	eye = Transform(mat, eye);

	return eye+center;
}

// Calculates the end point.

D3DVECTOR LookatPoint( D3DVECTOR eye, float angleH, float angleV, float length )
{
	D3DVECTOR	lookat;

	lookat = eye;
	lookat.z += length;

//?	RotatePoint(eye.x, eye.z, angleH, lookat.x, lookat.z);
//?	RotatePoint(eye.z, eye.y, angleV, lookat.z, lookat.y);
	RotatePoint(eye, angleH, angleV, lookat);

	return lookat;
}


// Returns the distance between two points.

float Length(FPOINT a, FPOINT b)
{
	return sqrtf( (a.x-b.x)*(a.x-b.x) +
				  (a.y-b.y)*(a.y-b.y) );
}

// Returns the hypotenuse of a right triangle.

float Length(float x, float y)
{
	return sqrtf( (x*x) + (y*y) );
}

// Returns the length of a vector.

float Length(const D3DVECTOR &u)
{
	return sqrtf( (u.x*u.x) + (u.y*u.y) + (u.z*u.z) );
}

// Returns the distance between two points.

float Length(const D3DVECTOR &a, const D3DVECTOR &b)
{
	return sqrtf( (a.x-b.x)*(a.x-b.x) +
				  (a.y-b.y)*(a.y-b.y) +
				  (a.z-b.z)*(a.z-b.z) );
}

// Returns the distance "a flat" between two points.

float Length2d(const D3DVECTOR &a, const D3DVECTOR &b)
{
	return sqrtf( (a.x-b.x)*(a.x-b.x) +
				  (a.z-b.z)*(a.z-b.z) );
}


// Returns the angle formed by two vectors.

float Angle( D3DVECTOR u, D3DVECTOR v )
{
#if 0
	return acosf( Abs(u.x*v.x + u.y*v.y + u.z*v.z) / (Length(u)*Length(v)) );
#endif
#if 0
	float	d;
	d = (u.y*v.z-u.z*v.y) + (u.z*v.x-u.x*v.z) + (u.x*v.y-u.y*v.x);
	return asinf( Abs(d) / (Length(u)*Length(v)) );
#endif
#if 0
	return asinf( Length(Cross(u,v)) / (Length(u)*Length(v)) );
#endif
#if 1
	float	len, a, b;

	len = Length(u)*Length(v);
	a = acosf( (u.x*v.x + u.y*v.y + u.z*v.z) / len );
	b = asinf( Length(Cross(u,v)) / len );
	return a;
#endif
}

// Returns the product of two vectors.

D3DVECTOR Cross( D3DVECTOR u, D3DVECTOR v )
{
	return D3DVECTOR( u.y*v.z - u.z*v.y,
					  u.z*v.x - u.x*v.z,
					  u.x*v.y - u.y*v.x );
}

// Returns the normal vector of a triangular face.

D3DVECTOR ComputeNormal( D3DVECTOR p1, D3DVECTOR p2, D3DVECTOR p3 )
{
	D3DVECTOR	u, v;

	u = D3DVECTOR( p3.x-p1.x, p3.y-p1.y, p3.z-p1.z );
	v = D3DVECTOR( p2.x-p1.x, p2.y-p1.y, p2.z-p1.z );

	return Normalize(Cross(u, v));
}


// Transforms a point in a matrix, in exactly the same manner as Direct3D.

D3DVECTOR Transform(const D3DMATRIX &m, D3DVECTOR p)
{
	D3DVECTOR	pp;

	pp.x = p.x*m._11 + p.y*m._21 + p.z*m._31 + m._41;
	pp.y = p.x*m._12 + p.y*m._22 + p.z*m._32 + m._42;
	pp.z = p.x*m._13 + p.y*m._23 + p.z*m._33 + m._43;

	return pp;
}


// Calculates the projection of a point P on a straight line AB.

D3DVECTOR Projection(const D3DVECTOR &a, const D3DVECTOR &b, const D3DVECTOR &p)
{
	float		k;

	k  = (b.x-a.x)*(p.x-a.x) + (b.y-a.y)*(p.y-a.y) + (b.z-a.z)*(p.z-a.z);
	k /= (b.x-a.x)*(b.x-a.x) + (b.y-a.y)*(b.y-a.y) + (b.z-a.z)*(b.z-a.z);

	return a + k*(b-a);
}

// The texture plate in the xz plane.

void MappingObject(D3DVERTEX2* pVertices, int nb, float scale)
{
	int		i;

	for ( i=0 ; i<nb ; i++ )
	{
		pVertices[i].tu = pVertices[i].x*scale;
		pVertices[i].tv = pVertices[i].z*scale;
	}
}

// Smooths normal.

void SmoothObject(D3DVERTEX2* pVertices, int nb)
{
	char*		bDone;
	int			index[100];
	int			i, j, rank;
	D3DVECTOR	sum;

	bDone = (char*)malloc(nb*sizeof(char));
	ZeroMemory(bDone, nb*sizeof(char));

	for ( i=0 ; i<nb ; i++ )
	{
		bDone[i] = TRUE;
		rank = 0;
		index[rank++] = i;

		for ( j=0 ; j<nb ; j++ )
		{
			if ( bDone[j] )  continue;
			if ( pVertices[j].x == pVertices[i].x &&
				 pVertices[j].y == pVertices[i].y &&
				 pVertices[j].z == pVertices[i].z )
			{
				bDone[j] = TRUE;
				index[rank++] = j;
				if ( rank >= 100 )  break;
			}
		}

		sum.x = 0;
		sum.y = 0;
		sum.z = 0;
		for ( j=0 ; j<rank ; j++ )
		{
			sum.x += pVertices[index[j]].nx;
			sum.y += pVertices[index[j]].ny;
			sum.z += pVertices[index[j]].nz;
		}
		sum = Normalize(sum);

		for ( j=0 ; j<rank ; j++ )
		{
			pVertices[index[j]].nx = sum.x;
			pVertices[index[j]].ny = sum.y;
			pVertices[index[j]].nz = sum.z;
		}
	}

	free(bDone);
}



// Calculates the parameters a and b of the segment passing
// through the points p1 and p2, knowing that:
//		f(x) = ax+b
// Returns FALSE if the line is vertical.

BOOL LineFunction(FPOINT p1, FPOINT p2, float &a, float &b)
{
	if ( D3DMath_IsZero(p1.x-p2.x) )
	{
		a = g_HUGE;  // infinite slope!
		b = p2.x;
		return FALSE;
	}

	a = (p2.y-p1.y)/(p2.x-p1.x);
	b = p2.y - p2.x*a;
	return TRUE;
}


// Calculates the distance between a plane ABC and a point P.

float DistancePlanPoint(const D3DVECTOR &a, const D3DVECTOR &b,
						const D3DVECTOR &c, const D3DVECTOR &p)
{
	D3DVECTOR	n;
	float		aa,bb,cc,dd;

	n = ComputeNormal(a,b,c);

	aa = n.x;
	bb = n.y;
	cc = n.z;
	dd = -(n.x*a.x + n.y*a.y + n.z*a.z);

	return Abs(aa*p.x + bb*p.y + cc*p.z + dd);
}

// Check if two planes defined by 3 points are part of the same plan.

BOOL IsSamePlane(D3DVECTOR *plan1, D3DVECTOR *plan2)
{
	D3DVECTOR	n1, n2;
	float		dist;

	n1 = ComputeNormal(plan1[0], plan1[1], plan1[2]);
	n2 = ComputeNormal(plan2[0], plan2[1], plan2[2]);

	if ( Abs(n1.x-n2.x) > 0.1f ||
		 Abs(n1.y-n2.y) > 0.1f ||
		 Abs(n1.z-n2.z) > 0.1f )  return FALSE;

	dist = DistancePlanPoint(plan1[0], plan1[1], plan1[2], plan2[0]);
	if ( dist > 0.1f )  return FALSE;

	return TRUE;
}


// Calculates the matrix to make three rotations in the X, Y and Z
// >>>>>> OPTIMIZING!!!

void MatRotateXZY(D3DMATRIX &mat, D3DVECTOR angle)
{
	D3DMATRIX	temp;

	D3DUtil_SetRotateXMatrix(temp, angle.x);
	D3DUtil_SetRotateZMatrix(mat, angle.z);
	D3DMath_MatrixMultiply(mat, mat, temp);
	D3DUtil_SetRotateYMatrix(temp, angle.y);
	D3DMath_MatrixMultiply(mat, mat, temp);  // X-Z-Y
}

// Calculates the matrix to make three rotations in the order Z, X and Y.
// >>>>>> OPTIMIZING!!!

void MatRotateZXY(D3DMATRIX &mat, D3DVECTOR angle)
{
	D3DMATRIX	temp;

	D3DUtil_SetRotateZMatrix(temp, angle.z);
	D3DUtil_SetRotateXMatrix(mat, angle.x);
	D3DMath_MatrixMultiply(mat, mat, temp);
	D3DUtil_SetRotateYMatrix(temp, angle.y);
	D3DMath_MatrixMultiply(mat, mat, temp);  // Z-X-Y
}


// Returns a random value between 0 and 1.

float Rand()
{
	return (float)rand()/RAND_MAX;
}


// Managing the dead zone of a joystick.

//  in:   -1            0            1
//       --|-------|----o----|-------|-->
//                      <---->
//                       dead
//  out:  -1       0         0       1

float Neutral(float value, float dead)
{
	if ( Abs(value) <= dead )
	{
		return 0.0f;
	}
	else
	{
		if ( value > 0.0f )  return (value-dead)/(1.0f-dead);
		else                 return (value+dead)/(1.0f-dead);
	}
}


// Calculates a value (radians) proportional between a and b (degrees).

float Prop(int a, int b, float p)
{
	float	aa, bb;

	aa = (float)a*PI/180.0f;
	bb = (float)b*PI/180.0f;

	return aa+p*(bb-aa);
}

// Gently advanced a desired value from its current value.
// Over time, the greater the progression is rapid.

float Smooth(float actual, float hope, float time)
{
	float	futur;

	futur = actual + (hope-actual)*time;

	if ( hope > actual )
	{
		if ( futur > hope )  futur = hope;
	}
	if ( hope < actual )
	{
		if ( futur < hope )  futur = hope;
	}

	return futur;
}


// Bounces any movement.

//	out
//	 |
//	1+------o-------o---
//	 |    o | o   o |  | bounce
//	 |   o  |   o---|---
//	 |  o   |       |
//	 | o    |       |
//	-o------|-------+----> progress
//	0|      |       1
//	 |<---->|middle

float Bounce(float progress, float middle, float bounce)
{
	if ( progress < middle )
	{
		progress = progress/middle;  // 0..1
		return 0.5f+sinf(progress*PI-PI/2.0f)/2.0f;
	}
	else
	{
		progress = (progress-middle)/(1.0f-middle);  // 0..1
		return (1.0f-bounce/2.0f)+sinf((0.5f+progress*2.0f)*PI)*(bounce/2.0f);
	}
}


// Returns the color corresponding D3DCOLOR.

D3DCOLOR RetColor(float intensity)
{
	D3DCOLOR	color;

	if ( intensity <= 0.0f )  return 0x00000000;
	if ( intensity >= 1.0f )  return 0xffffffff;

	color  = (int)(intensity*255.0f)<<24;
	color |= (int)(intensity*255.0f)<<16;
	color |= (int)(intensity*255.0f)<<8;
	color |= (int)(intensity*255.0f);

	return color;
}

// Returns the color corresponding D3DCOLOR.

D3DCOLOR RetColor(D3DCOLORVALUE intensity)
{
	D3DCOLOR	color;

	color  = (int)(intensity.a*255.0f)<<24;
	color |= (int)(intensity.r*255.0f)<<16;
	color |= (int)(intensity.g*255.0f)<<8;
	color |= (int)(intensity.b*255.0f);

	return color;
}

// Returns the color corresponding D3DCOLORVALUE.

D3DCOLORVALUE RetColor(D3DCOLOR intensity)
{
	D3DCOLORVALUE	color;

	color.r = (float)((intensity>>16)&0xff)/256.0f;
	color.g = (float)((intensity>>8 )&0xff)/256.0f;
	color.b = (float)((intensity>>0 )&0xff)/256.0f;
	color.a = (float)((intensity>>24)&0xff)/256.0f;

	return color;
}


// RGB to HSV conversion.

void RGB2HSV(D3DCOLORVALUE src, ColorHSV &dest)
{
	float	min, max, delta;

	min = Min(src.r, src.g, src.b);
	max = Max(src.r, src.g, src.b);

	dest.v = max;  // intensity

	if ( max == 0.0f )
	{
		dest.s = 0.0f;  // saturation
		dest.h = 0.0f;  // undefined color!
	}
	else
	{
		delta = max-min;
		dest.s = delta/max;  // saturation

		if ( src.r == max )  // between yellow & magenta
		{
			dest.h = (src.g-src.b)/delta;
		}
		else if ( src.g == max )  // between cyan & yellow
		{
			dest.h = 2.0f+(src.b-src.r)/delta;
		}
		else  // between magenta & cyan
		{
			dest.h = 4.0f+(src.r-src.g)/delta;
		}

		dest.h *= 60.0f;  // in degrees
		if ( dest.h < 0.0f )  dest.h += 360.0f;
		dest.h /= 360.0f;  // 0..1
	}
}

// HSV to RGB conversion.

void HSV2RGB(ColorHSV src, D3DCOLORVALUE &dest)
{
	int		i;
	float	f,v,p,q,t;

	src.h = Norm(src.h)*360.0f;
	src.s = Norm(src.s);
	src.v = Norm(src.v);

	if ( src.s == 0.0f )  // zero saturation?
	{
		dest.r = src.v;
		dest.g = src.v;
		dest.b = src.v;  // gray
	}
	else
	{
		if ( src.h == 360.0f )  src.h = 0.0f;
		src.h /= 60.0f;
		i = (int)src.h;  // integer part (0 .. 5)
		f = src.h-i;     // fractional part

		v = src.v;
		p = src.v*(1.0f-src.s);
		q = src.v*(1.0f-(src.s*f));
		t = src.v*(1.0f-(src.s*(1.0f-f)));

		switch (i)
		{
			case 0:  dest.r=v; dest.g=t; dest.b=p;  break;
			case 1:  dest.r=q; dest.g=v; dest.b=p;  break;
			case 2:  dest.r=p; dest.g=v; dest.b=t;  break;
			case 3:  dest.r=p; dest.g=q; dest.b=v;  break;
			case 4:  dest.r=t; dest.g=p; dest.b=v;  break;
			case 5:  dest.r=v; dest.g=p; dest.b=q;  break;
		}
	}
}