1 /* Copyright (C) 1992-1998 The Geometry Center
2 * Copyright (C) 1998-2000 Stuart Levy, Tamara Munzner, Mark Phillips
3 *
4 * This file is part of Geomview.
5 *
6 * Geomview is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU Lesser General Public License as published
8 * by the Free Software Foundation; either version 2, or (at your option)
9 * any later version.
10 *
11 * Geomview is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with Geomview; see the file COPYING. If not, write
18 * to the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139,
19 * USA, or visit http://www.gnu.org.
20 */
21
22 #if HAVE_CONFIG_H
23 # include "config.h"
24 #endif
25
26 #if 0
27 static char copyright[] = "Copyright (C) 1992-1998 The Geometry Center\n\
28 Copyright (C) 1998-2000 Stuart Levy, Tamara Munzner, Mark Phillips";
29 #endif
30
31 #include "mgP.h"
32 #include "mgpsP.h"
33
34
35 #define WCLIPPLANE 0.001 /* This is as close as we get to the eyeplane */
36
37 #define XLEFTCLIP 0.0
38 #define XRIGHTCLIP 0.0
39 #define YTOPCLIP 0.0
40 #define YBOTTOMCLIP 0.0
41 #define ZNEARCLIP (-1.0)
42 #define ZFARCLIP 1.0
43
44 static int xyz[6], clipvertnum = 0;
45 static mgpsprim *prim1, *prim2, *primtemp;
46 static CPoint3 *vts1, *vts2, *vtstemp;
47
48 /*
49 Function: mgps_dividew()
50 Description: Divide out w coordinate (*after* clipping against WCLIPPLANE)
51 Author: Daeron Meyer
52 */
53
mgps_dividew(void)54 void mgps_dividew(void)
55 {
56 CPoint3 *curr;
57 float w;
58 int n;
59
60 for (n = 0; n < prim1->numvts; n++) {
61 curr = &(vts1[n]);
62 w = curr->w; curr->x /= w; curr->y /= w; curr->z /= w;
63
64 curr->z += _mgpsc->znudgeby;
65
66 if (curr->x < XLEFTCLIP) xyz[0]++;
67 if (curr->x >= (float)_mgpsc->xsize - XRIGHTCLIP) xyz[1]++;
68 if (curr->y < YTOPCLIP) xyz[2]++;
69 if (curr->y >= (float)_mgpsc->ysize - YBOTTOMCLIP) xyz[3]++;
70 if (curr->z < ZNEARCLIP) xyz[4]++;
71 if (curr->z >= ZFARCLIP) xyz[5]++;
72
73 }
74 }
75
76 /*
77 Function: mgps_cliptoplane()
78 Description: Clip polygon against a coordinate axis plane
79 Author: Daeron Meyer
80 */
mgps_cliptoplane(int coord,float plane,float sign)81 void mgps_cliptoplane(int coord, float plane, float sign)
82 {
83 CPoint3 *prev, *curr, *dest;
84 float i, i1, i2, *c1, *p1, *d1;
85 int n;
86
87 #ifdef DEBUGCLIP
88 fprintf(stderr, "Clip %d, plane=%f, sign=%f\n", coord, plane, sign);
89 #endif
90 prim2->numvts = 0;
91 prev = &(vts1[prim1->numvts - 1]);
92 i1 = sign * ((float *) prev) [coord] - plane;
93
94 for (curr=vts1, n=prim1->numvts; n > 0; n--, prev=curr, i1=i2, curr++)
95 {
96 i2 = sign * ((float *) curr) [coord] - plane;
97 if ((i1 <= 0.0) ^ (i2 <= 0.0)) {
98 i = i1/(i1 - i2);
99 dest = &(vts2[prim2->numvts]);
100 dest->x = prev->x + i * (curr->x - prev->x);
101 dest->y = prev->y + i * (curr->y - prev->y);
102 dest->z = prev->z + i * (curr->z - prev->z);
103 dest->w = prev->w + i * (curr->w - prev->w);
104 if ((i1 <= 0.0) || (prev->drawnext == 0))
105 dest->drawnext = 0;
106 else
107 dest->drawnext = 1;
108 c1 = (float *) &(curr->vcol);
109 p1 = (float *) &(prev->vcol);
110 d1 = (float *) &(dest->vcol);
111 d1[0] = p1[0] + i * (c1[0] - p1[0]);
112 d1[1] = p1[1] + i * (c1[1] - p1[1]);
113 d1[2] = p1[2] + i * (c1[2] - p1[2]);
114 d1[3] = p1[3] + i * (c1[3] - p1[3]);
115 prim2->numvts++;
116 }
117 if (i2 <= 0.0)
118 {
119 vts2[prim2->numvts] = *curr;
120 prim2->numvts++;
121 }
122 }
123 #ifdef DEBUGCLIP
124 for (n = 0; n < prim2->numvts; n++)
125 {
126 fprintf(stderr, "%f, %f, %f, %f: %d\n",
127 vts2[n].x, vts2[n].y, vts2[n].z, vts2[n].w, vts2[n].drawnext);
128 }
129 #endif
130 }
131
132
133 /*
134 Function: mgps_primclip()
135 Description: Clip a polygon to fit in the viewing volume
136 Author: Daeron Meyer
137 */
mgps_primclip(mgpsprim * aprim)138 int mgps_primclip(mgpsprim *aprim)
139 {
140 static mgpsprim clip;
141 static int mykind, n;
142 static vvec clipverts;
143 static int intersectw;
144
145 xyz[0]=0; xyz[1]=0; xyz[2]=0; xyz[3]=0; xyz[4]=0; xyz[5]=0;
146
147 /* give ourselves more space for vertex data if needed */
148 if ((aprim->numvts * 2) > clipvertnum) {
149 if (!clipvertnum)
150 VVINIT(clipverts, CPoint3, clipvertnum);
151
152 clipvertnum = aprim->numvts * 2;
153 vvneeds(&clipverts, clipvertnum);
154 }
155
156 /* We might need more space for the final polygon since
157 clipping can produce a polygon with more vertices than
158 it had to begin with. We'll err on the side of safety: */
159
160 if ((_mgpsc->mysort->cvert + aprim->numvts) > _mgpsc->mysort->pvertnum)
161 {
162 _mgpsc->mysort->pvertnum *= 2;
163 vvneeds(&(_mgpsc->mysort->pverts), _mgpsc->mysort->pvertnum);
164 }
165
166 mykind = aprim->mykind;
167 prim1 = aprim; prim2 = &clip;
168 vts1 = &(VVEC(_mgpsc->mysort->pverts, CPoint3)[prim1->index]);
169 vts2 = &(VVEC(clipverts, CPoint3)[0]);
170
171 if ((mykind==PRIM_LINE) || (mykind==PRIM_SLINE))
172 vts1[prim1->numvts-1].drawnext = 0;
173
174 prim2->index = 0;
175 prim2->numvts = prim1->numvts;
176
177 #define CLIP_POLYS_AND_SWAP(a, b, c) { \
178 mgps_cliptoplane(a, b, c); \
179 if (prim2->numvts == 0) { aprim->numvts = 0; return PRIM_INVIS; } \
180 vtstemp = vts2; vts2 = vts1; vts1 = vtstemp; \
181 primtemp = prim2; prim2 = prim1; prim1 = primtemp; \
182 }
183
184
185 #ifdef DEBUGCLIP
186 fprintf(stderr, "BEGIN-CLIP\n");
187 fprintf(stderr, "INITIAL POLY:\n");
188 for (n=0; n < aprim->numvts; n++)
189 {
190 fprintf(stderr, "%f, %f, %f, %f: %d\n",
191 vts1[n].x, vts1[n].y, vts1[n].z, vts1[n].w, vts1[n].drawnext);
192 }
193 fprintf(stderr,"===========================\n");
194 #endif
195
196 intersectw = 0;
197 for (n = 0; (n < aprim->numvts) && !intersectw; n++)
198 {
199 if (vts1[n].w < WCLIPPLANE) intersectw = 1;
200 }
201
202 if (intersectw) CLIP_POLYS_AND_SWAP(3, -WCLIPPLANE, -1.0);
203
204 mgps_dividew();
205 n = prim1->numvts;
206
207 if (!intersectw && (xyz[0]+xyz[1]+xyz[2]+xyz[3]+xyz[4]+xyz[5] == 0))
208 return mykind;
209 else
210 if (xyz[0] == n || xyz[1] == n || xyz[2] == n ||
211 xyz[3] == n || xyz[4] == n || xyz[5] == n)
212 return PRIM_INVIS;
213
214 if (xyz[0]) CLIP_POLYS_AND_SWAP(0, -XLEFTCLIP, -1.0);
215 if (xyz[1]) CLIP_POLYS_AND_SWAP(0, (float)_mgpsc->xsize-XRIGHTCLIP, 1.0);
216 if (xyz[2]) CLIP_POLYS_AND_SWAP(1, -YTOPCLIP, -1.0);
217 if (xyz[3]) CLIP_POLYS_AND_SWAP(1, (float)_mgpsc->ysize-YBOTTOMCLIP, 1.0);
218 if (xyz[4]) CLIP_POLYS_AND_SWAP(2, -ZNEARCLIP, -1.0);
219 if (xyz[5]) CLIP_POLYS_AND_SWAP(2, ZFARCLIP, 1.0);
220
221
222 if (aprim == prim2) /* If the vertex data ended up in the local
223 vertex list, then we need to copy it back to the
224 global vertex list */
225 {
226 prim2->numvts = prim1->numvts;
227 /*
228 for (n=0; n < aprim->numvts; n++)
229 {
230 vts2[n] = vts1[n];
231 }
232 */
233 memcpy(vts2, vts1, sizeof(CPoint3) * prim1->numvts);
234
235 }
236
237 #ifdef DEBUGCLIP
238 fprintf(stderr, "FINAL POLY:\n");
239 for (n=0; n < aprim->numvts; n++)
240 {
241 fprintf(stderr, "%f, %f, %f, %f: %d\n",
242 vts1[n].x, vts1[n].y, vts1[n].z, vts1[n].w, vts1[n].drawnext);
243 }
244 fprintf(stderr, "END-CLIP\n");
245 #endif
246
247 return mykind;
248 }
249