3d/clipper.c

   1 /*
   2 THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
   3 SOFTWARE CORPORATION ("PARALLAX").  PARALLAX, IN DISTRIBUTING THE CODE TO
   4 END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
   5 ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
   6 IN USING, DISPLAYING,  AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
   7 SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
   8 FREE PURPOSES.  IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
   9 CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES.  THE END-USER UNDERSTANDS
  10 AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.
  11 COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
  12 */
  13
  14 #ifdef HAVE_CONFIG_H
  15 #include <conf.h>
  16 #endif
  17
  18 #include "3d.h"
  19 #include "globvars.h"
  20 #include "clipper.h"
  21 #include "error.h"
  22
  23 int free_point_num=0;
  24
  25 g3s_point temp_points[MAX_POINTS_IN_POLY];
  26 g3s_point *free_points[MAX_POINTS_IN_POLY];
  27
  28 void init_free_points(void)
  29 {
  30         int i;
  31
  32         for (i=0;i<MAX_POINTS_IN_POLY;i++)
  33                 free_points[i] = &temp_points[i];
  34 }
  35
  36
  37 g3s_point *get_temp_point()
  38 {
  39         g3s_point *p;
  40
  41         Assert (free_point_num < MAX_POINTS_IN_POLY );
  42         p = free_points[free_point_num++];
  43
  44         p->p3_flags = PF_TEMP_POINT;
  45
  46         return p;
  47 }
  48
  49 void free_temp_point(g3s_point *p)
  50 {
  51         Assert(p->p3_flags & PF_TEMP_POINT);
  52
  53         free_points[--free_point_num] = p;
  54
  55         p->p3_flags &= ~PF_TEMP_POINT;
  56 }
  57
  58 //clips an edge against one plane.
  59 g3s_point *clip_edge(int plane_flag,g3s_point *on_pnt,g3s_point *off_pnt)
  60 {
  61         fix psx_ratio;
  62         fix a,b,kn,kd;
  63         g3s_point *tmp;
  64
  65         //compute clipping value k = (xs-zs) / (xs-xe-zs+ze)
  66         //use x or y as appropriate, and negate x/y value as appropriate
  67
  68         if (plane_flag & (CC_OFF_RIGHT | CC_OFF_LEFT)) {
  69                 a = on_pnt->p3_x;
  70                 b = off_pnt->p3_x;
  71         }
  72         else {
  73                 a = on_pnt->p3_y;
  74                 b = off_pnt->p3_y;
  75         }
  76
  77         if (plane_flag & (CC_OFF_LEFT | CC_OFF_BOT)) {
  78                 a = -a;
  79                 b = -b;
  80         }
  81
  82         kn = a - on_pnt->p3_z;                                          //xs-zs
  83         kd = kn - b + off_pnt->p3_z;                            //xs-zs-xe+ze
  84
  85         tmp = get_temp_point();
  86
  87         psx_ratio = fixdiv( kn, kd );
  88
  89
  90 // PSX_HACK!!!!
  91 //      tmp->p3_x = on_pnt->p3_x + fixmuldiv(off_pnt->p3_x-on_pnt->p3_x,kn,kd);
  92 //      tmp->p3_y = on_pnt->p3_y + fixmuldiv(off_pnt->p3_y-on_pnt->p3_y,kn,kd);
  93
  94         tmp->p3_x = on_pnt->p3_x + fixmul( (off_pnt->p3_x-on_pnt->p3_x), psx_ratio);
  95         tmp->p3_y = on_pnt->p3_y + fixmul( (off_pnt->p3_y-on_pnt->p3_y), psx_ratio);
  96
  97         if (plane_flag & (CC_OFF_TOP|CC_OFF_BOT))
  98                 tmp->p3_z = tmp->p3_y;
  99         else
 100                 tmp->p3_z = tmp->p3_x;
 101
 102         if (plane_flag & (CC_OFF_LEFT|CC_OFF_BOT))
 103                 tmp->p3_z = -tmp->p3_z;
 104
 105         if (on_pnt->p3_flags & PF_UVS) {
 106 // PSX_HACK!!!!
 107 //              tmp->p3_u = on_pnt->p3_u + fixmuldiv(off_pnt->p3_u-on_pnt->p3_u,kn,kd);
 108 //              tmp->p3_v = on_pnt->p3_v + fixmuldiv(off_pnt->p3_v-on_pnt->p3_v,kn,kd);
 109                 tmp->p3_u = on_pnt->p3_u + fixmul((off_pnt->p3_u-on_pnt->p3_u), psx_ratio);
 110                 tmp->p3_v = on_pnt->p3_v + fixmul((off_pnt->p3_v-on_pnt->p3_v), psx_ratio);
 111
 112                 tmp->p3_flags |= PF_UVS;
 113         }
 114
 115         if (on_pnt->p3_flags & PF_LS) {
 116 // PSX_HACK
 117 //              tmp->p3_r = on_pnt->p3_r + fixmuldiv(off_pnt->p3_r-on_pnt->p3_r,kn,kd);
 118 //              tmp->p3_g = on_pnt->p3_g + fixmuldiv(off_pnt->p3_g-on_pnt->p3_g,kn,kd);
 119 //              tmp->p3_b = on_pnt->p3_b + fixmuldiv(off_pnt->p3_b-on_pnt->p3_b,kn,kd);
 120
 121                 tmp->p3_l = on_pnt->p3_l + fixmul((off_pnt->p3_l-on_pnt->p3_l), psx_ratio);
 122
 123                 tmp->p3_flags |= PF_LS;
 124         }
 125
 126         g3_code_point(tmp);
 127
 128         return tmp;
 129 }
 130
 131 //clips a line to the viewing pyramid.
 132 void clip_line(g3s_point **p0,g3s_point **p1,ubyte codes_or)
 133 {
 134         int plane_flag;
 135         g3s_point *old_p1;
 136
 137         //might have these left over
 138         (*p0)->p3_flags &= ~(PF_UVS|PF_LS);
 139         (*p1)->p3_flags &= ~(PF_UVS|PF_LS);
 140
 141         for (plane_flag=1;plane_flag<16;plane_flag<<=1)
 142                 if (codes_or & plane_flag) {
 143
 144                         if ((*p0)->p3_codes & plane_flag)
 145                                 {g3s_point *t=*p0; *p0=*p1; *p1=t;}     //swap!
 146
 147                         old_p1 = *p1;
 148
 149                         *p1 = clip_edge(plane_flag,*p0,*p1);
 150
 151                         if (old_p1->p3_flags & PF_TEMP_POINT)
 152                                 free_temp_point(old_p1);
 153                 }
 154
 155 }
 156
 157
 158 int clip_plane(int plane_flag,g3s_point **src,g3s_point **dest,int *nv,g3s_codes *cc)
 159 {
 160         int i;
 161         g3s_point **save_dest=dest;
 162
 163         //copy first two verts to end
 164         src[*nv] = src[0];
 165         src[*nv+1] = src[1];
 166
 167         cc->and = 0xff; cc->or = 0;
 168
 169         for (i=1;i<=*nv;i++) {
 170
 171                 if (src[i]->p3_codes & plane_flag) {                            //cur point off?
 172
 173                         if (! (src[i-1]->p3_codes & plane_flag)) {      //prev not off?
 174
 175                                 *dest = clip_edge(plane_flag,src[i-1],src[i]);
 176                                 cc->or  |= (*dest)->p3_codes;
 177                                 cc->and &= (*dest)->p3_codes;
 178                                 dest++;
 179                         }
 180
 181                         if (! (src[i+1]->p3_codes & plane_flag)) {
 182
 183                                 *dest = clip_edge(plane_flag,src[i+1],src[i]);
 184                                 cc->or  |= (*dest)->p3_codes;
 185                                 cc->and &= (*dest)->p3_codes;
 186                                 dest++;
 187                         }
 188
 189                         //see if must free discarded point
 190
 191                         if (src[i]->p3_flags & PF_TEMP_POINT)
 192                                 free_temp_point(src[i]);
 193                 }
 194                 else {                  //cur not off, copy to dest buffer
 195
 196                         *dest++ = src[i];
 197
 198                         cc->or  |= src[i]->p3_codes;
 199                         cc->and &= src[i]->p3_codes;
 200                 }
 201         }
 202
 203         return (dest-save_dest);
 204 }
 205
 206
 207 g3s_point **clip_polygon(g3s_point **src,g3s_point **dest,int *nv,g3s_codes *cc)
 208 {
 209         int plane_flag;
 210         g3s_point **t;
 211
 212         for (plane_flag=1;plane_flag<16;plane_flag<<=1)
 213
 214                 if (cc->or & plane_flag) {
 215
 216                         *nv = clip_plane(plane_flag,src,dest,nv,cc);
 217
 218                         if (cc->and)            //clipped away
 219                                 return dest;
 220
 221                         t = src; src = dest; dest = t;
 222
 223                 }
 224
 225         return src;             //we swapped after we copied
 226 }
 227