diff options
| -rw-r--r-- | graphics.h | 1 | ||||
| -rw-r--r-- | render.c | 64 |
2 files changed, 64 insertions, 1 deletions
@@ -67,6 +67,7 @@ Point3 world2vcs(Camera*, Point3); Point3 vcs2ndc(Camera*, Point3); Point3 world2ndc(Camera*, Point3); int isclipping(Point3); +int clipline3(Point3*, Point3*); Point toviewport(Camera*, Point3); Point2 fromviewport(Camera*, Point); void perspective(Matrix3, double, double, double, double); @@ -55,6 +55,68 @@ isclipping(Point3 p) return 0; } +/* Liang-Barsky algorithm, requires p0, p1 to be in NDC */ +int +clipline3(Point3 *p0, Point3 *p1) +{ + Point3 q0, q1, v; + int m0, m1, i; + double ti, to, th; + double c0[3*2] = { + p0->w + p0->x, p0->w - p0->x, p0->w + p0->y, + p0->w - p0->y, p0->z, p0->w - p0->z, + }, c1[3*2] = { + p1->w + p1->x, p1->w - p1->x, p1->w + p1->y, + p1->w - p1->y, p1->z, p1->w - p1->z, + }; + + /* bit-encoded regions */ + m0 = (c0[0] < 0) << 0 | + (c0[1] < 0) << 1 | + (c0[2] < 0) << 2 | + (c0[3] < 0) << 3 | + (c0[4] < 0) << 4 | + (c0[5] < 0) << 5; + m1 = (c1[0] < 0) << 0 | + (c1[1] < 0) << 1 | + (c1[2] < 0) << 2 | + (c1[3] < 0) << 3 | + (c1[4] < 0) << 4 | + (c1[5] < 0) << 5; + + if((m0 & m1) != 0) + return 1; /* trivially rejected */ + if((m0 | m1) == 0) + return 0; /* trivially accepted */ + + ti = 0; + to = 1; + for(i = 0; i < 3*2; i++){ + if(c1[i] < 0){ + th = c0[i] / (c0[i]-c1[i]); + if(th < to) + to = th; + }else if(c0[i] < 0){ + th = c0[i] / (c0[i]-c1[i]); + if(th < ti) + ti = th; + } + if(ti > to) + return 1; + } + + /* chop line to fit inside NDC */ + q0 = *p0; + q1 = *p1; + v = subpt3(q1, q0); + if(m0 != 0) + *p0 = addpt3(q0, mulpt3(v, ti)); + if(m1 != 0) + *p1 = addpt3(q0, mulpt3(v, to)); + + return 0; +} + Point toviewport(Camera *c, Point3 p) { @@ -112,7 +174,7 @@ line3(Camera *c, Point3 p0, Point3 p1, int end0, int end1, Image *src) { p0 = world2ndc(c, p0); p1 = world2ndc(c, p1); - if(isclipping(p0) || isclipping(p1)) + if(clipline3(&p0, &p1)) return; line(c->viewport, toviewport(c, p0), toviewport(c, p1), end0, end1, 0, src, ZP); } |