2 THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
3 SOFTWARE CORPORATION ("PARALLAX"). PARALLAX, IN DISTRIBUTING THE CODE TO
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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
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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.
28 g3s_point temp_points[MAX_POINTS_IN_POLY];
29 g3s_point *free_points[MAX_POINTS_IN_POLY];
31 void init_free_points(void)
35 for (i=0;i<MAX_POINTS_IN_POLY;i++)
36 free_points[i] = &temp_points[i];
40 g3s_point *get_temp_point()
44 Assert (free_point_num < MAX_POINTS_IN_POLY );
45 p = free_points[free_point_num++];
47 p->p3_flags = PF_TEMP_POINT;
52 void free_temp_point(g3s_point *p)
54 Assert(p->p3_flags & PF_TEMP_POINT);
56 free_points[--free_point_num] = p;
58 p->p3_flags &= ~PF_TEMP_POINT;
61 //clips an edge against one plane.
62 g3s_point *clip_edge(int plane_flag,g3s_point *on_pnt,g3s_point *off_pnt)
68 //compute clipping value k = (xs-zs) / (xs-xe-zs+ze)
69 //use x or y as appropriate, and negate x/y value as appropriate
71 if (plane_flag & (CC_OFF_RIGHT | CC_OFF_LEFT)) {
80 if (plane_flag & (CC_OFF_LEFT | CC_OFF_BOT)) {
85 kn = a - on_pnt->p3_z; //xs-zs
86 kd = kn - b + off_pnt->p3_z; //xs-zs-xe+ze
88 tmp = get_temp_point();
90 psx_ratio = fixdiv( kn, kd );
94 // tmp->p3_x = on_pnt->p3_x + fixmuldiv(off_pnt->p3_x-on_pnt->p3_x,kn,kd);
95 // tmp->p3_y = on_pnt->p3_y + fixmuldiv(off_pnt->p3_y-on_pnt->p3_y,kn,kd);
97 tmp->p3_x = on_pnt->p3_x + fixmul( (off_pnt->p3_x-on_pnt->p3_x), psx_ratio);
98 tmp->p3_y = on_pnt->p3_y + fixmul( (off_pnt->p3_y-on_pnt->p3_y), psx_ratio);
100 if (plane_flag & (CC_OFF_TOP|CC_OFF_BOT))
101 tmp->p3_z = tmp->p3_y;
103 tmp->p3_z = tmp->p3_x;
105 if (plane_flag & (CC_OFF_LEFT|CC_OFF_BOT))
106 tmp->p3_z = -tmp->p3_z;
108 if (on_pnt->p3_flags & PF_UVS) {
110 // tmp->p3_u = on_pnt->p3_u + fixmuldiv(off_pnt->p3_u-on_pnt->p3_u,kn,kd);
111 // tmp->p3_v = on_pnt->p3_v + fixmuldiv(off_pnt->p3_v-on_pnt->p3_v,kn,kd);
112 tmp->p3_u = on_pnt->p3_u + fixmul((off_pnt->p3_u-on_pnt->p3_u), psx_ratio);
113 tmp->p3_v = on_pnt->p3_v + fixmul((off_pnt->p3_v-on_pnt->p3_v), psx_ratio);
115 tmp->p3_flags |= PF_UVS;
118 if (on_pnt->p3_flags & PF_LS) {
120 // tmp->p3_r = on_pnt->p3_r + fixmuldiv(off_pnt->p3_r-on_pnt->p3_r,kn,kd);
121 // tmp->p3_g = on_pnt->p3_g + fixmuldiv(off_pnt->p3_g-on_pnt->p3_g,kn,kd);
122 // tmp->p3_b = on_pnt->p3_b + fixmuldiv(off_pnt->p3_b-on_pnt->p3_b,kn,kd);
124 tmp->p3_l = on_pnt->p3_l + fixmul((off_pnt->p3_l-on_pnt->p3_l), psx_ratio);
126 tmp->p3_flags |= PF_LS;
134 //clips a line to the viewing pyramid.
135 void clip_line(g3s_point **p0,g3s_point **p1,ubyte codes_or)
140 //might have these left over
141 (*p0)->p3_flags &= ~(PF_UVS|PF_LS);
142 (*p1)->p3_flags &= ~(PF_UVS|PF_LS);
144 for (plane_flag=1;plane_flag<16;plane_flag<<=1)
145 if (codes_or & plane_flag) {
147 if ((*p0)->p3_codes & plane_flag)
148 {g3s_point *t=*p0; *p0=*p1; *p1=t;} //swap!
152 *p1 = clip_edge(plane_flag,*p0,*p1);
154 if (old_p1->p3_flags & PF_TEMP_POINT)
155 free_temp_point(old_p1);
161 int clip_plane(int plane_flag,g3s_point **src,g3s_point **dest,int *nv,g3s_codes *cc)
164 g3s_point **save_dest=dest;
166 //copy first two verts to end
170 cc->and = 0xff; cc->or = 0;
172 for (i=1;i<=*nv;i++) {
174 if (src[i]->p3_codes & plane_flag) { //cur point off?
176 if (! (src[i-1]->p3_codes & plane_flag)) { //prev not off?
178 *dest = clip_edge(plane_flag,src[i-1],src[i]);
179 cc->or |= (*dest)->p3_codes;
180 cc->and &= (*dest)->p3_codes;
184 if (! (src[i+1]->p3_codes & plane_flag)) {
186 *dest = clip_edge(plane_flag,src[i+1],src[i]);
187 cc->or |= (*dest)->p3_codes;
188 cc->and &= (*dest)->p3_codes;
192 //see if must free discarded point
194 if (src[i]->p3_flags & PF_TEMP_POINT)
195 free_temp_point(src[i]);
197 else { //cur not off, copy to dest buffer
201 cc->or |= src[i]->p3_codes;
202 cc->and &= src[i]->p3_codes;
206 return (dest-save_dest);
210 g3s_point **clip_polygon(g3s_point **src,g3s_point **dest,int *nv,g3s_codes *cc)
215 for (plane_flag=1;plane_flag<16;plane_flag<<=1)
217 if (cc->or & plane_flag) {
219 *nv = clip_plane(plane_flag,src,dest,nv,cc);
221 if (cc->and) //clipped away
224 t = src; src = dest; dest = t;
228 return src; //we swapped after we copied