OpenGL (SDL,C++) - ray tracing - functions.cpp

//http://www.youtube.com/user/thecplusplusguy
//watch the video for explonation
//ray-sphere and ray-plane collision detection.
//if you find a bug, let me know
//the other files are the same, as earlier, download those, if you want to run.
#include "functions.h"

float camX=0.0,camY=0.0,camZ=5.0;
float camYaw=0.0;
float camPitch=0.0;
enum {SKY_LEFT=0,SKY_BACK,SKY_RIGHT,SKY_FRONT,SKY_TOP,SKY_BOTTOM};
unsigned int skybox[6];
#ifndef M_PI
#define M_PI 3.1415926535
#endif


void initskybox()
{
    skybox[SKY_LEFT]=loadTexture("left.bmp");
    skybox[SKY_BACK]=loadTexture("back.bmp");
    skybox[SKY_RIGHT]=loadTexture("right.bmp");
    skybox[SKY_FRONT]=loadTexture("front.bmp");
    skybox[SKY_TOP]=loadTexture("top.bmp");
    skybox[SKY_BOTTOM]=loadTexture("bottom.bmp");
}

void killskybox()
{
    glDeleteTextures(6,&skybox[0]);
}

void lockCamera()
{
    if(camPitch>90)
        camPitch=90;
    if(camPitch<-90)
        camPitch=-90;
    if(camYaw<0.0)
        camYaw+=360.0;
    if(camYaw>360.0)
        camYaw-=360;
}

void moveCamera(float dist,float dir)
{
    float rad=(camYaw+dir)*M_PI/180.0;
    camX-=sin(rad)*dist;
    camZ-=cos(rad)*dist;
}

void moveCameraUp(float dist,float dir)
{
    float rad=(camPitch+dir)*M_PI/180.0;
    camY+=sin(rad)*dist;
}

void Control(float movevel,float mousevel,bool mi)
{
    if(mi)
    {
        int MidX=320;
        int MidY=240;
        SDL_ShowCursor(SDL_DISABLE);
        int tmpx,tmpy;
        SDL_GetMouseState(&tmpx,&tmpy);
        camYaw+=mousevel*(MidX-tmpx);
        camPitch+=mousevel*(MidY-tmpy);
        lockCamera();
        SDL_WarpMouse(MidX,MidY);
        Uint8* state=SDL_GetKeyState(NULL);
        if(state[SDLK_w])
        {
            if(camPitch!=90 && camPitch!=-90)
                moveCamera(movevel,0.0);
            moveCameraUp(movevel,0.0);
        }else if(state[SDLK_s])
        {
            if(camPitch!=90 && camPitch!=-90)
                moveCamera(movevel,180.0);
            moveCameraUp(movevel,180.0);
        }
        if(state[SDLK_a])
            moveCamera(movevel,90.0);
        else if(state[SDLK_d])
            moveCamera(movevel,270);
    }
    glRotatef(-camPitch,1.0,0.0,0.0);
    glRotatef(-camYaw,0.0,1.0,0.0);
}

void UpdateCamera()
{
    glTranslatef(-camX,-camY,-camZ);
}

void drawCube(float size)
{
    float difamb[]={1.0,0.5,0.3,1.0};
    glBegin(GL_QUADS);
        //front face
        glMaterialfv(GL_FRONT_AND_BACK,GL_AMBIENT_AND_DIFFUSE,difamb);
        glNormal3f(0.0,0.0,1.0);
        glVertex3f(size/2,size/2,size/2);
        glVertex3f(-size/2,size/2,size/2);
        glVertex3f(-size/2,-size/2,size/2);
        glVertex3f(size/2,-size/2,size/2);

        //left face
        glNormal3f(-1.0,0.0,0.0);
        glVertex3f(-size/2,size/2,size/2);
        glVertex3f(-size/2,size/2,-size/2);
        glVertex3f(-size/2,-size/2,-size/2);
        glVertex3f(-size/2,-size/2,size/2);

        //back face
        glNormal3f(0.0,0.0,-1.0);
        glVertex3f(size/2,size/2,-size/2);
        glVertex3f(-size/2,size/2,-size/2);
        glVertex3f(-size/2,-size/2,-size/2);
        glVertex3f(size/2,-size/2,-size/2);

        //right face
        glNormal3f(1.0,0.0,0.0);
        glVertex3f(size/2,size/2,-size/2);
        glVertex3f(size/2,size/2,size/2);
        glVertex3f(size/2,-size/2,size/2);
        glVertex3f(size/2,-size/2,-size/2);

        //top face
        glNormal3f(0.0,1.0,0.0);
        glVertex3f(size/2,size/2,size/2);
        glVertex3f(-size/2,size/2,size/2);
        glVertex3f(-size/2,size/2,-size/2);
        glVertex3f(size/2,size/2,-size/2);

        //bottom face
        glNormal3f(0.0,-1.0,0.0);
        glVertex3f(size/2,-size/2,size/2);
        glVertex3f(-size/2,-size/2,size/2);
        glVertex3f(-size/2,-size/2,-size/2);
        glVertex3f(size/2,-size/2,-size/2);
    glEnd();
}

void drawSkybox(float size)
{
    glDisable(GL_LIGHTING);
    glDisable(GL_DEPTH_TEST);
    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D,skybox[SKY_BACK]);
    glBegin(GL_QUADS);
        //back face
        glTexCoord2f(0,0);
        glVertex3f(size/2,size/2,size/2);
        glTexCoord2f(1,0);
        glVertex3f(-size/2,size/2,size/2);
        glTexCoord2f(1,1);
        glVertex3f(-size/2,-size/2,size/2);
        glTexCoord2f(0,1);
        glVertex3f(size/2,-size/2,size/2);
    glEnd();
    glBindTexture(GL_TEXTURE_2D,skybox[SKY_LEFT]);
    glBegin(GL_QUADS);
        //left face
        glTexCoord2f(0,0);
        glVertex3f(-size/2,size/2,size/2);
        glTexCoord2f(1,0);
        glVertex3f(-size/2,size/2,-size/2);
        glTexCoord2f(1,1);
        glVertex3f(-size/2,-size/2,-size/2);
        glTexCoord2f(0,1);
        glVertex3f(-size/2,-size/2,size/2);
    glEnd();
    glBindTexture(GL_TEXTURE_2D,skybox[SKY_FRONT]);
    glBegin(GL_QUADS);
        //front face
        glTexCoord2f(1,0);
        glVertex3f(size/2,size/2,-size/2);
        glTexCoord2f(0,0);
        glVertex3f(-size/2,size/2,-size/2);
        glTexCoord2f(0,1);
        glVertex3f(-size/2,-size/2,-size/2);
        glTexCoord2f(1,1);
        glVertex3f(size/2,-size/2,-size/2);
    glEnd();
    glBindTexture(GL_TEXTURE_2D,skybox[SKY_RIGHT]);
    glBegin(GL_QUADS);
        //right face
        glTexCoord2f(0,0);
        glVertex3f(size/2,size/2,-size/2);
        glTexCoord2f(1,0);
        glVertex3f(size/2,size/2,size/2);
        glTexCoord2f(1,1);
        glVertex3f(size/2,-size/2,size/2);
        glTexCoord2f(0,1);
        glVertex3f(size/2,-size/2,-size/2);
    glEnd();
    glBindTexture(GL_TEXTURE_2D,skybox[SKY_TOP]);
    glBegin(GL_QUADS);          //top face
        glTexCoord2f(1,0);
        glVertex3f(size/2,size/2,size/2);
        glTexCoord2f(0,0);
        glVertex3f(-size/2,size/2,size/2);
        glTexCoord2f(0,1);
        glVertex3f(-size/2,size/2,-size/2);
        glTexCoord2f(1,1);
        glVertex3f(size/2,size/2,-size/2);
    glEnd();
    glBindTexture(GL_TEXTURE_2D,skybox[SKY_BOTTOM]);
    glBegin(GL_QUADS);
        //bottom face
        glTexCoord2f(1,1);
        glVertex3f(size/2,-size/2,size/2);
        glTexCoord2f(0,1);
        glVertex3f(-size/2,-size/2,size/2);
        glTexCoord2f(0,0);
        glVertex3f(-size/2,-size/2,-size/2);
        glTexCoord2f(1,0);
        glVertex3f(size/2,-size/2,-size/2);
    glEnd();
    glEnable(GL_LIGHTING);
    glEnable(GL_DEPTH_TEST);
    glDisable(GL_TEXTURE_2D);
}

bool raysphere(float xc,float yc, float zc,float xd,float yd, float zd,float xs,float ys, float zs,float r)
{
    float b=2*(xd*(xs-xc)+yd*(ys-yc)+zd*(zs-zc));
    float c=xs*xs-2*xs*xc+xc*xc+ys*ys-2*ys*yc+yc*yc+zs*zs-2*zs*zc+zc*zc-r*r;
    float disc=(b*b-4*c);
    if(disc<0)
        return false;
    else
        return true;
        //(x+y)^2=x^2+2xy+y^2
}

bool rayplane(float nx,float ny,float nz,float xs,float ys,float zs,float xd,float yd,float zd,coordinate p1,coordinate p2,coordinate p3,coordinate p4)
{
    float a=xd*nx+yd*ny+zd*nz;
    if(a==0)
        return false;
    float t=((p1.x*nx+p1.y*ny+p1.z*nz-nx*xs-ny*ys-nz*zs)/a);
    if(t<0)
        return false;
    float x=xs+t*xd;
    float y=ys+t*yd;
    float z=zs+t*zd;
    coordinate cp(x,y,z);
    if(abs(trianglearea(p1,p3,p4)-trianglearea(p1,p4,cp)-trianglearea(p1,p3,cp)-trianglearea(p3,p4,cp))<0.000001 || abs(trianglearea(p1,p2,p3)-trianglearea(p1,p2,cp)-trianglearea(p2,p3,cp)-trianglearea(p1,p3,cp))<0.000001)
        return true;
    return false;
}


float trianglearea(coordinate p1,coordinate p2,coordinate p3)
{
        //area of the triangle with the heron fomula
        float a=sqrt((p2.x-p1.x)*(p2.x-p1.x)+(p2.y-p1.y)*(p2.y-p1.y)+(p2.z-p1.z)*(p2.z-p1.z));
        float b=sqrt((p3.x-p2.x)*(p3.x-p2.x)+(p3.y-p2.y)*(p3.y-p2.y)+(p3.z-p2.z)*(p3.z-p2.z));
        float c=sqrt((p1.x-p3.x)*(p1.x-p3.x)+(p1.y-p3.y)*(p1.y-p3.y)+(p1.z-p3.z)*(p1.z-p3.z));
        float s=(a+b+c)/2.;
        return (sqrt(s*((s-a)*(s-b)*(s-c))));

}


unsigned int loadTexture(const char* filename)
{
    unsigned int num;
    glGenTextures(1,&num);
    SDL_Surface* img=SDL_LoadBMP(filename);
    glBindTexture(GL_TEXTURE_2D,num);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
//  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP);
//  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP);
    glTexImage2D(GL_TEXTURE_2D,0,GL_RGB,img->w,img->h,0,GL_RGB,GL_UNSIGNED_SHORT_5_6_5,img->pixels);
    SDL_FreeSurface(img);
    return num;
}