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 #include <conf.h>
  14 #include "fix.h"
  15 #include "vecmat.h"
  16 #include "gr.h"
  17 #include "3d.h"
  18 #include "globvars.h"
  19 #include "clipper.h"
  20 #include "error.h"
  21
  22 int free_point_num=0;
  23
  24 g3s_point temp_points[MAX_POINTS_IN_POLY];
  25 g3s_point *free_points[MAX_POINTS_IN_POLY];
  26
  27 void init_free_points(void)
  28 {
  29         int i;
  30
  31         for (i=0;i<MAX_POINTS_IN_POLY;i++)
  32                 free_points[i] = &temp_points[i];
  33 }
  34
  35
  36 g3s_point *get_temp_point()
  37 {
  38         g3s_point *p;
  39
  40         Assert (free_point_num < MAX_POINTS_IN_POLY );
  41         p = free_points[free_point_num++];
  42
  43         p->p3_flags = PF_TEMP_POINT;
  44
  45         return p;
  46 }
  47
  48 void free_temp_point(g3s_point *p)
  49 {
  50         Assert(p->p3_flags & PF_TEMP_POINT);
  51
  52         free_points[--free_point_num] = p;
  53
  54         p->p3_flags &= ~PF_TEMP_POINT;
  55 }
  56
  57 //clips an edge against one plane.
  58 g3s_point *clip_edge(int plane_flag,g3s_point *on_pnt,g3s_point *off_pnt)
  59 {
  60         fix psx_ratio;
  61         fix a,b,kn,kd;
  62         g3s_point *tmp;
  63
  64         //compute clipping value k = (xs-zs) / (xs-xe-zs+ze)
  65         //use x or y as appropriate, and negate x/y value as appropriate
  66
  67         if (plane_flag & (CC_OFF_RIGHT | CC_OFF_LEFT)) {
  68                 a = on_pnt->p3_x;
  69                 b = off_pnt->p3_x;
  70         }
  71         else {
  72                 a = on_pnt->p3_y;
  73                 b = off_pnt->p3_y;
  74         }
  75
  76         if (plane_flag & (CC_OFF_LEFT | CC_OFF_BOT)) {
  77                 a = -a;
  78                 b = -b;
  79         }
  80
  81         kn = a - on_pnt->p3_z;                                          //xs-zs
  82         kd = kn - b + off_pnt->p3_z;                            //xs-zs-xe+ze
  83
  84         tmp = get_temp_point();
  85
  86         psx_ratio = fixdiv( kn, kd );
  87
  88
  89 // PSX_HACK!!!!
  90 //      tmp->p3_x = on_pnt->p3_x + fixmuldiv(off_pnt->p3_x-on_pnt->p3_x,kn,kd);
  91 //      tmp->p3_y = on_pnt->p3_y + fixmuldiv(off_pnt->p3_y-on_pnt->p3_y,kn,kd);
  92
  93         tmp->p3_x = on_pnt->p3_x + fixmul( (off_pnt->p3_x-on_pnt->p3_x), psx_ratio);
  94         tmp->p3_y = on_pnt->p3_y + fixmul( (off_pnt->p3_y-on_pnt->p3_y), psx_ratio);
  95
  96         if (plane_flag & (CC_OFF_TOP|CC_OFF_BOT))
  97                 tmp->p3_z = tmp->p3_y;
  98         else
  99                 tmp->p3_z = tmp->p3_x;
 100
 101         if (plane_flag & (CC_OFF_LEFT|CC_OFF_BOT))
 102                 tmp->p3_z = -tmp->p3_z;
 103
 104         if (on_pnt->p3_flags & PF_UVS) {
 105 // PSX_HACK!!!!
 106 //              tmp->p3_u = on_pnt->p3_u + fixmuldiv(off_pnt->p3_u-on_pnt->p3_u,kn,kd);
 107 //              tmp->p3_v = on_pnt->p3_v + fixmuldiv(off_pnt->p3_v-on_pnt->p3_v,kn,kd);
 108                 tmp->p3_u = on_pnt->p3_u + fixmul((off_pnt->p3_u-on_pnt->p3_u), psx_ratio);
 109                 tmp->p3_v = on_pnt->p3_v + fixmul((off_pnt->p3_v-on_pnt->p3_v), psx_ratio);
 110
 111                 tmp->p3_flags |= PF_UVS;
 112         }
 113
 114         if (on_pnt->p3_flags & PF_LS) {
 115 // PSX_HACK
 116 //              tmp->p3_r = on_pnt->p3_r + fixmuldiv(off_pnt->p3_r-on_pnt->p3_r,kn,kd);
 117 //              tmp->p3_g = on_pnt->p3_g + fixmuldiv(off_pnt->p3_g-on_pnt->p3_g,kn,kd);
 118 //              tmp->p3_b = on_pnt->p3_b + fixmuldiv(off_pnt->p3_b-on_pnt->p3_b,kn,kd);
 119
 120                 tmp->p3_l = on_pnt->p3_l + fixmul((off_pnt->p3_l-on_pnt->p3_l), psx_ratio);
 121
 122                 tmp->p3_flags |= PF_LS;
 123         }
 124
 125         g3_code_point(tmp);
 126
 127         return tmp;
 128 }
 129
 130 //clips a line to the viewing pyramid.
 131 void clip_line(g3s_point **p0,g3s_point **p1,ubyte codes_or)
 132 {
 133         int plane_flag;
 134         g3s_point *old_p1;
 135
 136         //might have these left over
 137         (*p0)->p3_flags &= ~(PF_UVS|PF_LS);
 138         (*p1)->p3_flags &= ~(PF_UVS|PF_LS);
 139
 140         for (plane_flag=1;plane_flag<16;plane_flag<<=1)
 141                 if (codes_or & plane_flag) {
 142
 143                         if ((*p0)->p3_codes & plane_flag)
 144                                 {g3s_point *t=*p0; *p0=*p1; *p1=t;}     //swap!
 145
 146                         old_p1 = *p1;
 147
 148                         *p1 = clip_edge(plane_flag,*p0,*p1);
 149
 150                         if (old_p1->p3_flags & PF_TEMP_POINT)
 151                                 free_temp_point(old_p1);
 152                 }
 153
 154 }
 155
 156
 157 int clip_plane(int plane_flag,g3s_point **src,g3s_point **dest,int *nv,g3s_codes *cc)
 158 {
 159         int i;
 160         g3s_point **save_dest=dest;
 161
 162         //copy first two verts to end
 163         src[*nv] = src[0];
 164         src[*nv+1] = src[1];
 165
 166         cc->and = 0xff; cc->or = 0;
 167
 168         for (i=1;i<=*nv;i++) {
 169
 170                 if (src[i]->p3_codes & plane_flag) {                            //cur point off?
 171
 172                         if (! (src[i-1]->p3_codes & plane_flag)) {      //prev not off?
 173
 174                                 *dest = clip_edge(plane_flag,src[i-1],src[i]);
 175                                 cc->or  |= (*dest)->p3_codes;
 176                                 cc->and &= (*dest)->p3_codes;
 177                                 dest++;
 178                         }
 179
 180                         if (! (src[i+1]->p3_codes & plane_flag)) {
 181
 182                                 *dest = clip_edge(plane_flag,src[i+1],src[i]);
 183                                 cc->or  |= (*dest)->p3_codes;
 184                                 cc->and &= (*dest)->p3_codes;
 185                                 dest++;
 186                         }
 187
 188                         //see if must free discarded point
 189
 190                         if (src[i]->p3_flags & PF_TEMP_POINT)
 191                                 free_temp_point(src[i]);
 192                 }
 193                 else {                  //cur not off, copy to dest buffer
 194
 195                         *dest++ = src[i];
 196
 197                         cc->or  |= src[i]->p3_codes;
 198                         cc->and &= src[i]->p3_codes;
 199                 }
 200         }
 201
 202         return (dest-save_dest);
 203 }
 204
 205
 206 g3s_point **clip_polygon(g3s_point **src,g3s_point **dest,int *nv,g3s_codes *cc)
 207 {
 208         int plane_flag;
 209         g3s_point **t;
 210
 211         for (plane_flag=1;plane_flag<16;plane_flag<<=1)
 212
 213                 if (cc->or & plane_flag) {
 214
 215                         *nv = clip_plane(plane_flag,src,dest,nv,cc);
 216
 217                         if (cc->and)            //clipped away
 218                                 return dest;
 219
 220                         t = src; src = dest; dest = t;
 221
 222                 }
 223
 224         return src;             //we swapped after we copied
 225 }
 226