CPSC 102 Computer Science II
(Advanced C Programming)
Assignment 1

Objectives:

Description:

1. Using the code developed in lab 4, namely the plane_print function, write the plane_hits function to calculate the ray/plane intersection, if any.
2. Among others, provide the function

   	double plane_hits(object_t *obj, vec_t base, vec_t dir);
   	

   to test whether the ray defined by base and dir intersects the plane object. Recall that this function is pointed to by the generic object's function pointer

   	double     (*hits)(struct object_type*,vec_t,vec_t);
   	

3. Your code should be such that the following main() and test_hits() routines work unaltered:

   int main()
   {
           list_t          *mats;
           list_t          *objs;
           material_t      *mat;
           object_t        *obj;
           char            token[16];
           drgb_t          pix;
           vec_t           pos = { 4.0,  3.0,  5.0};
           vec_t           dir = { 0.0,  0.0, -1.0};
           int             firsttime=1;
   
     // create material and object lists
     mats = list_init();
     objs = list_init();
   
     // input should consist of material definitions followed by
     // object definitions
     while(fscanf(stdin,"%s",token) == 1) {
   
       if(!strcmp(token,"material")) {
         // create material_t structure and read attributes
         material_init(stdin,mats,0);
   
         // this test is designed to ensure that list_add
         // pointed current to the material just loaded
         mat = (material_t *)list_get_data(mats);
         assert(mat->cookie == MAT_COOKIE);
         fprintf(stderr,"loaded %s \n",material_getname(mat));
       }
   
       if(!strcmp(token,"plane")) {
         // create plane object
         plane_init(stdin,objs,mats,0);
   
         // this test is designed to ensure that list_add
         // pointed current to the object just loaded
         obj = (object_t *)list_get_data(objs);
         assert(obj->cookie == OBJ_COOKIE);
         fprintf(stderr,"loaded %s \n",object_getname(obj));
   
         // test hits function
         pos[0] =  4.0; pos[1] =  3.0; pos[2] =  5.0;
         dir[0] =  0.0; dir[1] =  0.0; dir[2] = -1.0;
         test_hits(obj,pos,dir);
   
         if(firsttime) {
           // make sure we don't get a hit on a miss...shoot
           // straight down at backwall
           fprintf(stderr,"vertical ray test\n");
           pos[0] =  4.0; pos[1] =  3.0; pos[2] =  5.0;
           dir[0] =  0.0; dir[1] = -2.1; dir[2] =  0.0;
           test_hits(obj,pos,dir);
           firsttime = 1-firsttime;
         } else {
           // make sure we don't get a hit in +z space
           fprintf(stderr,"positive z test\n");
           pos[0] =  4.0; pos[1] =  3.0; pos[2] =  5.0;
           dir[0] =  0.0; dir[1] = -2.1; dir[2] = -1.0;
           test_hits(obj,pos,dir);
         }
       }
     }
   
     // verify that we have all materials
     material_list_print(mats,stdout);
   
     // verify that we have all objects
     object_list_print(objs,stdout);
   
     return(0);
   }
   
   void test_hits(object_t *obj,vec_t pos,vec_t dir)
   {
           double  dist=0.0;
   
     vec_unit(dir,dir);
     memset(obj->last_hit,0,sizeof(vec_t));
     dist = obj->hits(obj,pos,dir);
   
     fprintf(stderr,"dist to plane %s %8.3lf \n",obj->name,dist);
     vec_print(stderr,"hit point",obj->last_hit);
   }
   	

4. Sample input:
   

   material green
   {
      ambient 0 5 0
   }
   
   material brown
   {
      ambient 3 3 0
   }
   
   plane wall
   {
      material green
      normal 0 0 1
      point  0 0 -7
   }
   
   plane floor
   {
      material brown
      normal 0 1 1
      point  0 0 -7
   }
   	

5. Sample output:
   

   loaded green 
   loaded brown 
   loaded wall 
   dist to plane wall   12.000 
   hit point   4.000   3.000  -7.000
   vertical ray test
   dist to plane wall   -1.000 
   hit point   0.000   0.000   0.000
   loaded floor 
   dist to plane floor   15.000 
   hit point   4.000   3.000 -10.000
   positive z test
   dist to plane floor   -1.000 
   hit point   4.000  -7.161   0.161
   material green
   {
      ambient 0 5 0
   }
   
   material brown
   {
      ambient 3 3 0
   }
   
   plane wall
   {
      material green
      normal 0 0 1
      point  0 0 -7
   }
   
   plane floor
   {
      material brown
      normal 0 1 1
      point  0 0 -7
   }
   	

What to hand in:

1. A README file containing
   1. Course id--section no
   2. Name
   3. Assignment description
   4. Brief solution description (e.g., program design, description of algorithm, etc., however appropriate).
   5. Lessons learned, identified interesting features of your program
   6. Any special usage instructions
2. Makefile
3. source code (.h headers and .c source)
4. object code (do a make clean before tar)

How to hand in: