CMPS-3480 Computer Graphics
Lab-7

• Ray tracing
• Building an object list
• Render a scene
• Create a gif animation

Lab-8 code from Wednesday for dent in sphere



-------------------------------
structs...
-------------------------------
struct Clip {
    Vec center;
    Vec normal;
    Flt radius;
    int inside;
    Clip() {
        radius = 0.0;
        inside = 1;
    }
};

struct Object {
    int type;
    int inside;
    Vec center;
    Vec norm;
    Vec tri[3];
    Flt radius, radius2;
    Vec color;
    int surface;
    bool specular;
    Vec spec;
    Clip clip;
    int nclips;
    Object() {
        nclips = 0;
        inside = 0;
    }
};

-------------------------------
function...
-------------------------------

void vecNegate(Vec v)
{
    v[0] = -v[0];
    v[1] = -v[1];
    v[2] = -v[2];
}       

-------------------------------
from init()...
-------------------------------

	//big ball
	o = &g.object[g.nobjects];
	o->type = TYPE_SPHERE;
	vecMake(0.0, 200.0, 0.0, o->center);
	vecMake(1.0, 0.0, 0.0, o->color);
	o->radius = 200.0;
	o->specular = true;
	o->specular = 0;
	vecMake(0.3, 0.3, 0.3, o->spec);
	o->surface = SURF_NONE;
	//add a clip
	vecMake(50.0, 380.0, 90.0, o->clip.center);
	o->clip.radius = 60.0;
	++o->nclips;
	g.nobjects++;
	//
	//small ball for dent
	o = &g.object[g.nobjects];
	o->type = TYPE_SPHERE;
	vecMake(50.0, 380.0, 90.0, o->center);
	vecMake(1.0, 0.0, 0.0, o->color);
	o->radius = 60.0;
	o->specular = true;
	o->specular = 0;
	vecMake(0.3, 0.3, 0.3, o->spec);
	o->surface = SURF_NONE;
	o->inside = 1;
	//add a clip
	vecMake(0.0, 200.0, 0.0, o->clip.center);
	o->clip.radius = 200.0;
	o->clip.inside = 0;
	++o->nclips;
	g.nobjects++;

-------------------------------
from raySphereIntersect()...
-------------------------------
    if (t0 > 0.0) {
        hit->p[0] = ray->o[0] + ray->d[0] * t0;
        hit->p[1] = ray->o[1] + ray->d[1] * t0;
        hit->p[2] = ray->o[2] + ray->d[2] * t0;
        sphereNormal(hit->p, o->center, hit->norm);
        //if (o->inside)
        //  vecNegate(hit->norm);
        hit->t = t0;
        if (o->nclips > 0) {
            if (o->clip.radius != 0.0) {
                //clipping sphere
                Vec v;
                vecSub(o->clip.center, hit->p, v);
                Flt dist = sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2]);
                if (o->clip.inside) {
                    if (dist <= o->clip.radius)
                        goto t1;
                } else {
                    if (dist >= o->clip.radius)
                        goto t1;
                }
            }
        }
        return 1;
    }
t1:;
    if (t1 > 0.0) {
        hit->p[0] = ray->o[0] + ray->d[0] * t1;
        hit->p[1] = ray->o[1] + ray->d[1] * t1;
        hit->p[2] = ray->o[2] + ray->d[2] * t1;
        sphereNormal(hit->p, o->center, hit->norm);
        //if (o->inside)
        //  vecNegate(hit->norm);
        hit->t = t1;
        if (o->nclips > 0) {
            if (o->clip.radius != 0.0) {
                //clipping sphere
                Vec v;
                vecSub(o->clip.center, hit->p, v);
                Flt dist = sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2]);
                if (o->clip.inside) {
                    if (dist <= o->clip.radius)
                        return 0;
                } else {
                    if (dist >= o->clip.radius)
                        return 0;
                }
            }
        }
        return 1;
    }

-------------------------------
from trace()...
-------------------------------

           case TYPE_SPHERE:
                if (raySphereIntersect(o, ray, &hit)) {
                    if (hit.t < closehit.t) {
                        closehit.t = hit.t;
                        vecCopy(hit.p, closehit.p);
                        vecCopy(o->color, closehit.color);
                        sphereNormal(closehit.p, o->center, closehit.norm);
                        if (o->inside)
                            vecNegate(closehit.norm);
                        h = i;
                    }
                }
                break;






-------------------------------
spherical texture...
-------------------------------



Name your texture image file: lab8a.png

    //This goes inside the trace() function

    if (o->surface == SURF_SPHERICAL_TEXTURE) {
        //Get the spherical texture color based on the hit-point normal.
        //Must have Image class from lab-1.
        //
        const Flt PI = 3.14159265358979;
        const Flt PIdiv2 = PI / 2.0;
        const Flt PItimes2 = PI * 2.0;
        Vec vn;
        vecCopy(closehit.norm, vn);
        //Use normal.y to get an angle
        Flt pct = asin(vn[1]) / PIdiv2;
        //pct might be positive or negative
        Flt h2 = (Flt)img.height * 0.5;
        //Get the row in the image stream
        Flt row = h2 + (pct * h2);
        //Get the angle of hitpoint going around the sphere
        Flt col_angle = atan2(vn[2], vn[0]);
        //Use angle to get the column in the image stream
        Flt col = ((col_angle + PI) / PItimes2) * (Flt)img.width;
        //flip y and x coordinates
        row = img.height - row - 1;
        col = img.width - col - 1;
        //Get row and column to use in pointer arithmetic
        int y = (int)row;
        int x = (int)col;
        //Get the spot within the image stream
        int spot = y * img.width * 3 + x * 3;
        //Get pointer to the pixel stream.
        unsigned char *p = img.data;
        //Get the red, green, blue colors.
        closehit.color[0] = (Flt)(*(p + (spot + 0))) / 255.0;
        closehit.color[1] = (Flt)(*(p + (spot + 1))) / 255.0;
        closehit.color[2] = (Flt)(*(p + (spot + 2))) / 255.0;
    }

Log into Odin, using the -YC option.
   example: ssh -YC myname@odin

Do this:

   $ cd 3480
   $ ./lab-start.sh
   $ cd 7
   $ cp /home/fac/gordon/p/3480/code/7/* .
   $ make
   $ ./lab7

Press M

Step 1: render a scene similar to the one below



This scene is also possible




Step 2: create a short animation

   Follow along with Gordon to produce an animation

Step 3: make your own ray-traced animation

   1. Animation must loop forever.

   2. Animation must be seamless.

      Viewer does not know where it starts or ends.
      
      It can go up and down, left and right, or around.

      You may make the checkerboard floor texture move or change
	  to give the appearance of the camera following an object..

      Use the objects given.

   3. Create gif animation from program.

      Create your gif animation at the command-line something like this:

	     convert -delay  -loop 0 *.png mylab7.gif

      Your program will capture frames and create the gif animation
	  on a key press. Add the key to your menu.

   4. Make a web page at public_html/3480/lab7.html

      Display your animations.


//=======================================================================
Screen shot function that produces .png files

PNG is about 95% smaller than a PPM file.

void takeScreenshot(const char *filename, int reset)
{
    //This function will capture your current X11 window,
    //and save it to a PPM P6 image file.
    //File names are generated sequentially.
    static int picnum = 0;
    int x,y;
    int width, height;
    x11.getWindowAttributes(&width, &height);
    if (reset)
        picnum = 0;
    XImage *image = x11.getImage(width, height);
    //
    //If filename argument is empty, generate a sequential filename...
    char ts[200] = "";
    char png[200] = "";
    strcpy(ts, filename);
    strcpy(png, filename);
    if (ts[0] == '\0') {
        sprintf(ts,"./lab7%02i.ppm", picnum);
        sprintf(png,"./lab7%02i.png", picnum);
        picnum++;
    }
    FILE *fpo = fopen(ts, "w");
    if (fpo) {
        fprintf(fpo, "P6\n%i %i\n255\n", width, height);
        for (y=0; y<height; y++) {
            for (x=0; x<width; x++) {
                unsigned long pixel = XGetPixel(image, x, y);
                fputc(((pixel & 0x00ff0000)>>16), fpo);
                fputc(((pixel & 0x0000ff00)>> 8), fpo);
                fputc(((pixel & 0x000000ff)    ), fpo);
            }
        }
        fclose(fpo);
    }
    XFree(image);
    char str[450];
    sprintf(str, "convert %s %s", ts, png);
    system(str);
    unlink(ts);
}
//=======================================================================

1. vi card.cpp
2. Copy and paste the code below.
3. g++ card.cpp -lm -o card
4. ./card > image.ppm
5. display image.ppm

---------------------------------------
#include <stdlib.h>   // card > aek.ppm
#include <stdio.h>
#include <math.h>
typedef int i;typedef float f;struct v{
f x,y,z;v operator+(v r){return v(x+r.x
,y+r.y,z+r.z);}v operator*(f r){return
v(x*r,y*r,z*r);}f operator%(v r){return
x*r.x+y*r.y+z*r.z;}v(){}v operator^(v r
){return v(y*r.z-z*r.y,z*r.x-x*r.z,x*r.
y-y*r.x);}v(f a,f b,f c){x=a;y=b;z=c;}v
operator!(){return*this*(1/sqrt(*this%*
this));}};i G[]={247570,280596,280600,
249748,18578,18577,231184,16,16};f R(){
return(f)rand()/RAND_MAX;}i T(v o,v d,f
&t,v&n){t=1e9;i m=0;f p=-o.z/d.z;if(.01
<p)t=p,n=v(0,0,1),m=1;for(i k=19;k--;)
for(i j=9;j--;)if(G[j]&1<<k){v p=o+v(-k
,0,-j-4);f b=p%d,c=p%p-1,q=b*b-c;if(q>0
){f s=-b-sqrt(q);if(s<t&&s>.01)t=s,n=!(
p+d*t),m=2;}}return m;}v S(v o,v d){f t
;v n;i m=T(o,d,t,n);if(!m)return v(.7,
.6,1)*pow(1-d.z,4);v h=o+d*t,l=!(v(9+R(
),9+R(),16)+h*-1),r=d+n*(n%d*-2);f b=l%
n;if(b<0||T(h,l,t,n))b=0;f p=pow(l%r*(b
>0),99);if(m&1){h=h*.2;return((i)(ceil(
h.x)+ceil(h.y))&1?v(3,1,1):v(3,3,3))*(b
*.2+.1);}return v(p,p,p)+S(h,r)*.5;}i
main(){printf("P6 512 512 255 ");v g=!v
(-6,-16,0),a=!(v(0,0,1)^g)*.002,b=!(g^a
)*.002,c=(a+b)*-256+g;for(i y=512;y--;)
for(i x=512;x--;){v p(13,13,13);for(i r
=64;r--;){v t=a*(R()-.5)*99+b*(R()-.5)*
99;p=S(v(17,16,8)+t,!(t*-1+(a*(R()+x)+b
*(y+R())+c)*16))*3.5+p;}printf("%c%c%c"
,(i)p.x,(i)p.y,(i)p.z);}}
---------------------------------------

Reference
https://fabiensanglard.net/revisiting_the_businesscard_raytracer/