| /* |
| ** |
| ** Copyright 2007, The Android Open Source Project |
| ** |
| ** Licensed under the Apache License, Version 2.0 (the "License"); |
| ** you may not use this file except in compliance with the License. |
| ** You may obtain a copy of the License at |
| ** |
| ** http://www.apache.org/licenses/LICENSE-2.0 |
| ** |
| ** Unless required by applicable law or agreed to in writing, software |
| ** distributed under the License is distributed on an "AS IS" BASIS, |
| ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| ** See the License for the specific language governing permissions and |
| ** limitations under the License. |
| */ |
| |
| /* |
| * Generic Convex Polygon Scan Conversion and Clipping |
| * by Paul Heckbert |
| * from "Graphics Gems", Academic Press, 1990 |
| */ |
| |
| /* Based on the public domain code: |
| * poly_clip.c: homogeneous 3-D convex polygon clipper |
| * |
| * Paul Heckbert 1985, Dec 1989 |
| */ |
| |
| #include "poly.h" |
| #include "string.h" |
| |
| #define LOG_TAG "StreetView" |
| #include <utils/Log.h> |
| |
| namespace android { |
| |
| #define SWAP(a, b, temp) {(temp) = a; (a) = b; (b) = temp;} |
| #define COORD(vert, i) ((float *)(vert))[i] |
| |
| #define CLIP_AND_SWAP(elem, sign, k, p, q, r) { \ |
| poly_clip_to_halfspace(p, q, &v->elem-(float *)v, sign, (sign)*(k)); \ |
| if ((q)->n==0) {p1->n = 0; return POLY_CLIP_OUT;} \ |
| SWAP(p, q, r); \ |
| } |
| |
| /* |
| * poly_clip_to_halfspace: clip convex polygon p against a plane, |
| * copying the portion satisfying sign*s[index] < k*sw into q, |
| * where s is a Poly_vert* cast as a float*. |
| * index is an index into the array of floats at each vertex, such that |
| * s[index] is sx, sy, or sz (screen space x, y, or z). |
| * Thus, to clip against xmin, use |
| * poly_clip_to_halfspace(p, q, XINDEX, -1., -xmin); |
| * and to clip against xmax, use |
| * poly_clip_to_halfspace(p, q, XINDEX, 1., xmax); |
| */ |
| |
| void poly_clip_to_halfspace(Poly* p, Poly* q, int index, float sign, float k) |
| { |
| float *up, *vp, *wp; |
| Poly_vert *v; |
| int i; |
| Poly_vert *u; |
| float t, tu, tv; |
| |
| q->n = 0; |
| |
| /* start with u=vert[n-1], v=vert[0] */ |
| u = &p->vert[p->n-1]; |
| tu = sign*COORD(u, index) - u->sw*k; |
| for (v= &p->vert[0], i=p->n; i>0; i--, u=v, tu=tv, v++) { |
| /* on old polygon (p), u is previous vertex, v is current vertex */ |
| /* tv is negative if vertex v is in */ |
| tv = sign*COORD(v, index) - v->sw*k; |
| if ((tu <= 0.0f) ^ (tv <= 0.0f)) { |
| /* edge crosses plane; add intersection point to q */ |
| t = tu/(tu-tv); |
| up = (float *)u; |
| vp = (float *)v; |
| wp = (float *)&q->vert[q->n].sx; |
| for(int i = 0; i < 4; i++, wp++, up++, vp++) { |
| *wp = *up+t*(*vp-*up); |
| } |
| q->n++; |
| } |
| if (tv<=0.0f) /* vertex v is in, copy it to q */ |
| q->vert[q->n++] = *v; |
| } |
| } |
| |
| /* |
| * poly_clip_to_frustum: Clip the convex polygon p1 to the screen space frustum |
| * using the homogeneous screen coordinates (sx, sy, sz, sw) of each vertex, |
| * testing if v->sx/v->sw > box->x0 and v->sx/v->sw < box->x1, |
| * and similar tests for y and z, for each vertex v of the polygon. |
| * If polygon is entirely inside box, then POLY_CLIP_IN is returned. |
| * If polygon is entirely outside box, then POLY_CLIP_OUT is returned. |
| * Otherwise, if the polygon is cut by the box, p1 is modified and |
| * POLY_CLIP_PARTIAL is returned. |
| * |
| * Given an n-gon as input, clipping against 6 planes could generate an |
| * (n+6)gon, so POLY_NMAX in poly.h must be big enough to allow that. |
| */ |
| |
| int poly_clip_to_frustum(Poly *p1) |
| { |
| int x0out = 0, x1out = 0, y0out = 0, y1out = 0, z0out = 0, z1out = 0; |
| int i; |
| Poly_vert *v; |
| Poly p2, *p, *q, *r; |
| |
| /* count vertices "outside" with respect to each of the six planes */ |
| for (v=p1->vert, i=p1->n; i>0; i--, v++) { |
| float sw = v->sw; |
| if (v->sx < -sw) x0out++; /* out on left */ |
| if (v->sx > sw) x1out++; /* out on right */ |
| if (v->sy < -sw) y0out++; /* out on top */ |
| if (v->sy > sw) y1out++; /* out on bottom */ |
| if (v->sz < -sw) z0out++; /* out on near */ |
| if (v->sz > sw) z1out++; /* out on far */ |
| } |
| |
| /* check if all vertices inside */ |
| if (x0out+x1out+y0out+y1out+z0out+z1out == 0) |
| return POLY_CLIP_IN; |
| |
| /* check if all vertices are "outside" any of the six planes */ |
| if (x0out==p1->n || x1out==p1->n || y0out==p1->n || |
| y1out==p1->n || z0out==p1->n || z1out==p1->n) { |
| p1->n = 0; |
| return POLY_CLIP_OUT; |
| } |
| |
| /* |
| * now clip against each of the planes that might cut the polygon, |
| * at each step toggling between polygons p1 and p2 |
| */ |
| p = p1; |
| q = &p2; |
| if (x0out) CLIP_AND_SWAP(sx, -1.0f, -1.0f, p, q, r); |
| if (x1out) CLIP_AND_SWAP(sx, 1.0f, 1.0f, p, q, r); |
| if (y0out) CLIP_AND_SWAP(sy, -1.0f, -1.0f, p, q, r); |
| if (y1out) CLIP_AND_SWAP(sy, 1.0f, 1.0f, p, q, r); |
| if (z0out) CLIP_AND_SWAP(sz, -1.0f, -1.0f, p, q, r); |
| if (z1out) CLIP_AND_SWAP(sz, 1.0f, 1.0f, p, q, r); |
| |
| /* if result ended up in p2 then copy it to p1 */ |
| if (p==&p2) |
| memcpy(p1, &p2, sizeof(Poly)-(POLY_NMAX-p2.n)*sizeof(Poly_vert)); |
| return POLY_CLIP_PARTIAL; |
| } |
| |
| } // namespace android |