//Accurate 3D Modeling of Molecules
//Ben  Parr
//Period 6

#include <stdio.h>
#include <GL/glut.h>
#include <stdlib.h>
#include <math.h>

#define N 1000

double theta=90.0,phi=90.0,oldphi=90.0,MAX=3.0;//spherical coordinates of eye position
double up=1.0,zoomangle=90.0;
int xmouse=-1,ymouse=-1;
int bondnum=0,atomnum=0;//number of bonds and atoms in model
int w;
double xDiff,yDiff,zDiff,tempHeight,otherDist,tempAngle;//used for bond/cylinder positioning
double bradius=.05;//bond radius
GLUquadricObj *quadratic;

struct atom
{
	double x,y,z;//location
	double radius;
	double red,green,blue;//color
};
struct bond
{
	int type;//single bond=1, double bond=2
	struct atom * a;
	struct atom * b;
};

struct atom Atoms[N];
struct bond Bonds[N];

void init()
{
	//initialize quadratic for cylinders
	quadratic=gluNewQuadric();
	gluQuadricNormals(quadratic, GLU_SMOOTH);

	//set background color to gray
	glClearColor(0.75, 0.75, 0.75, 0.0);

	//initialize lighting
	GLfloat shine[]= {50.0};
	glMaterialfv(GL_FRONT, GL_SHININESS, shine);
	GLfloat lightPos[] = { 2.5f, 2.5f, 4.0f, 1.0f };
	glLightfv(GL_LIGHT0, GL_POSITION, lightPos);
	
	glShadeModel(GL_SMOOTH);

	glEnable(GL_COLOR_MATERIAL);
	glEnable(GL_LIGHTING);
	glEnable(GL_LIGHT0);
	glEnable(GL_DEPTH_TEST);
}

double distance(double tempX,double tempY,double tempZ)
{
	return sqrt(pow(tempX,2)+pow(tempY,2)+pow(tempZ,2));
}

void changeView()
{
        //reposition eye
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

	//convert spherical coordinates to cartesian coordinates
	double x=MAX*sin(phi*(M_PI/180.0))*cos(theta*(M_PI/180.0));
	double y=MAX*sin(phi*(M_PI/180.0))*sin(theta*(M_PI/180.0));
	double z=MAX*cos(phi*(M_PI/180.0));
	gluLookAt(x,y,z,0.0,0.0,0.0,0.0,0.0,up);
}

void zoom()
{
	/*
	 * zooming funtion is created by 
	 * calling gluPerspecive with 
	 * a different angle 
	*/
	glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        gluPerspective(zoomangle,1.0,.01,100.0);
}

void mouse(int button, int state, int x, int y)
{
	if(button==3)//mouse wheel up
	{
		//zoom in
		if(zoomangle>2.0)
			zoomangle-=1.0;
		zoom();
		changeView();
		glutPostRedisplay();
	}
	else if(button==4)//mouse wheel down
	{
		//zoom out
		if(zoomangle<177.0)
			zoomangle+=1.0;
		zoom();
		changeView();
		glutPostRedisplay();
	}
	else if(button==GLUT_LEFT_BUTTON&&state==GLUT_DOWN)
	{
		xmouse=x;
		ymouse=y;
		oldphi=phi;
	}
	else
	{
		xmouse=-1;
		ymouse=-1;
	}
}

void motion(int x,int y)
{
	if(xmouse!=-1 && ymouse!=-1)
	{
		//update spherical coordinates
		theta+=(xmouse-x)/2.0;
		phi+=(ymouse-y)/2.0;
		
		//keep phi between -90.0 and 90.0
		phi=((int)((phi+540.0)*10.0))%3600/10.0-180.0;
		if(phi*oldphi<0)
		{
			oldphi=phi;
			up=-up;
		}
		xmouse=x;
		ymouse=y;
		
		changeView();
		glutPostRedisplay();
	}
}

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
	
	//draw atoms
	for(w=0;w<atomnum;w++)
	{
		glPushMatrix();
			glColor3d(Atoms[w].red,Atoms[w].green,Atoms[w].blue);
			glTranslatef(Atoms[w].x,Atoms[w].y,Atoms[w].z);
			glutSolidSphere(Atoms[w].radius,50,50);
		glPopMatrix();
	}
	
	glColor3f(.5,.5,.5);
	
	//draw bonds
	for(w=0;w<bondnum;w++)
	{
		glPushMatrix();
			xDiff=Bonds[w].b->x-Bonds[w].a->x;
			yDiff=Bonds[w].b->y-Bonds[w].a->y;
			zDiff=Bonds[w].b->z-Bonds[w].a->z;
			tempHeight=distance(xDiff,yDiff,zDiff);
			if(tempHeight>0.0 && (xDiff!=0.0 || yDiff!=0.0))
			{
				glTranslatef(Bonds[w].a->x,Bonds[w].a->y,Bonds[w].a->z);
				glRotatef(acos(zDiff/tempHeight)*180.0/M_PI,0.0,1.0,0.0);
				otherDist=distance(xDiff,yDiff,0.0);
				tempAngle=acos(xDiff/otherDist)*180.0/M_PI;
				if(yDiff<0.0)
					tempAngle*=-1.0;
				glRotatef(tempAngle,-otherDist,0.0,zDiff);
			}
			else if(xDiff==0.0 && yDiff==0.0 && tempHeight>0.0)
			{
				if(zDiff>0.0)
					 glTranslatef(Bonds[w].a->x,Bonds[w].a->y,Bonds[w].a->z);
				else
					glTranslatef(Bonds[w].b->x,Bonds[w].b->y,Bonds[w].b->z);
			}

			gluCylinder(quadratic,bradius,bradius,tempHeight,50,50);
		glPopMatrix();
	}
	
	//draw axis
	glBegin(GL_LINES);
		glColor3f(0.0,0.0,0.0);
		glVertex3f(1.,0.0,0.0);
		glVertex3f(-1.,0.0,0.0);
		glVertex3f(0.0,1.,0.0);
		glVertex3f(0.0,-1.,0.0);
		glVertex3f(0.0,0.0,1.);
		glVertex3f(0.0,0.0,-1.);
	glEnd();

	glutSwapBuffers();
}

void addAtom(double tempX,double tempY,double tempZ,double tempRadius,double tempRed,double tempGreen,double tempBlue)
{
	struct atom tempAtom;
	tempAtom.x=tempX;
	tempAtom.y=tempY;
	tempAtom.z=tempZ;
	tempAtom.radius=tempRadius;
	tempAtom.red=tempRed;
	tempAtom.green=tempGreen;
	tempAtom.blue=tempBlue;

	Atoms[atomnum]=tempAtom;
	atomnum++;
}

void addBond(int tempType,int tempAtom1,int tempAtom2)
{
	struct bond tempBond;
	tempBond.type=tempType;
	tempBond.a=&Atoms[tempAtom1];
	tempBond.b=&Atoms[tempAtom2];

	Bonds[bondnum]=tempBond;
	bondnum++;
}

void createFirstMol()
{
	//create a methane molecule
	addAtom(0.0,0.0,0.0,.3,1.0,0.0,0.0);
	addAtom(.8,0.5,-.6,.2,0.0,0.0,1.0);
	addAtom(-.8,0.5,-.6,.2,0.0,0.0,1.0);
	addAtom(0.0,0.5,1.0,.2,0.0,0.0,1.0);
	addAtom(0.0,-1.1,0.0,.2,0.0,0.0,1.0);
	
	addBond(1,0,1);
	addBond(1,0,2);
	addBond(1,0,3);
	addBond(1,0,4);
}

int main(int argc,char** argv)
{  
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);
	glutInitWindowSize(600,600);
	glutInitWindowPosition(50,50);
	glutCreateWindow("3D Model");
	
	init();
	createFirstMol();

	zoom();
	changeView();

	glutDisplayFunc(display);
	glutMouseFunc(mouse);
	glutMotionFunc(motion);
	glutMainLoop();

	return 0;
}