mathdefs.cpp

本程序描述的是一个三维织物动感模拟系统。计算机生成真实感服装被列入计算机图形学亟需解决的三大问题之一。

///////////////////////////////////////////////////////////////////////////////
//
// MathDefs.cpp : implementation file
//
// Purpose:	Implementation of Math Routines
//
// Created:
//		JL  2/18/98
// Revisions:
//
///////////////////////////////////////////////////////////////////////////////
//
//	Copyright 1998 Jeff Lander, All Rights Reserved.
//  For educational purposes only.
//  Please do not republish in electronic or print form without permission
//  Thanks - [e-mail]
//
///////////////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include <math.h>
#include "mathdefs.h"

///////////////////////////////////////////////////////////////////////////////
// Function:	MultVectorByMatrix
// Purpose:		Multiplies a vector by a 4x4 Matrix in OpenGL Format
// Arguments:	Matrix, Vector in, and result Vector
// Notes:		This routing is tweaked to handle OpenGLs column-major format
//				This is one obvious place for optimization perhaps asm code
///////////////////////////////////////////////////////////////////////////////
void MultVectorByMatrix(tMatrix *mat, tVector *v,tVector *result)
{
	result->x = (mat->m[0] * v->x) +
			   (mat->m[4] * v->y) +	
			   (mat->m[8] * v->z) +
			   mat->m[12];
	result->y = (mat->m[1] * v->x) +
			   (mat->m[5] * v->y) +	
			   (mat->m[9] * v->z) +
			   mat->m[13];
	result->z = (mat->m[2] * v->x) +
			   (mat->m[6] * v->y) +	
			   (mat->m[10] * v->z) +
			   mat->m[14];
}
//// MultVectorByMatrix //////////////////////////////////////////////////////


/* returns squared length of input vector */    
double VectorSquaredLength(tVector *v) 
{
	return((v->x * v->x) + (v->y * v->y) + (v->z * v->z));
}

/* returns length of input vector */
double VectorLength(tVector *v) 
{
	return(sqrt(VectorSquaredLength(v)));
}

/* destructively normalizes the input vector */
void NormalizeVector(tVector *v) 
{
	float len = (float)VectorLength(v);
    if (len != 0.0) 
	{ 
		v->x /= len;  
		v->y /= len; 
		v->z /= len; 
	}
}

double DotProduct(tVector *v1, tVector *v2)
{
	return ((v1->x * v2->x) + (v1->y * v2->y) + (v1->z * v2->z));
}

/* return the cross product result = v1 cross v2 */
void CrossProduct(tVector *v1, tVector *v2, tVector *result)
{
	result->x = (v1->y * v2->z) - (v1->z * v2->y);
	result->y = (v1->z * v2->x) - (v1->x * v2->z);
	result->z = (v1->x * v2->y) - (v1->y * v2->x);
}

double VectorSquaredDistance(tVector *v1, tVector *v2) 
{
	return(	((v1->x - v2->x) * (v1->x - v2->x)) + 
			((v1->y - v2->y) * (v1->y - v2->y)) + 	
			((v1->z - v2->z) * (v1->z - v2->z)) ); 	
}

void ScaleVector(tVector *v, float scale, tVector *result) 
{
	result->x = v->x * scale;
	result->y = v->y * scale;
	result->z = v->z * scale;
}

void VectorSum(tVector *v1, tVector *v2, tVector *result) 
{
	result->x = v1->x + v2->x;
	result->y = v1->y + v2->y;
	result->z = v1->z + v2->z;
}

void VectorDifference(tVector *v1, tVector *v2, tVector *result) 
{
	result->x = v1->x - v2->x;
	result->y = v1->y - v2->y;
	result->z = v1->z - v2->z;
}