diff options
| -rw-r--r-- | geometry.h | 7 | ||||
| -rw-r--r-- | point.c | 5 | ||||
| -rw-r--r-- | triangle.c | 33 |
3 files changed, 43 insertions, 2 deletions
@@ -56,6 +56,7 @@ Point2 lerp2(Point2, Point2, double); double dotvec2(Point2, Point2); double vec2len(Point2); Point2 normvec2(Point2); +int edgeptcmp(Point2, Point2, Point2); int ptinpoly(Point2, Point2*, ulong); /* Point3 */ @@ -118,8 +119,12 @@ Point3 rframexform3(Point3, RFrame3); Point2 invrframexform(Point2, RFrame); Point3 invrframexform3(Point3, RFrame3); +/* Triangle2 */ +Point2 centroid(Triangle2); +Point3 barycoords(Triangle2, Point2); + /* Triangle3 */ -Point3 centroid(Triangle3); +Point3 centroid3(Triangle3); /* Fmt */ #pragma varargck type "v" Point2 @@ -79,6 +79,11 @@ normvec2(Point2 v) * * Juan Pineda, “A Parallel Algorithm for Polygon Rasterization”, * Computer Graphics, Vol. 22, No. 8, August 1988 + * + * comparison of a point p with an edge [e0 e1] + * p to the right: + + * p to the left: - + * p on the edge: 0 */ int edgeptcmp(Point2 e0, Point2 e1, Point2 p) @@ -2,8 +2,39 @@ #include <libc.h> #include <geometry.h> +/* 2D */ + +Point2 +centroid(Triangle2 t) +{ + return divpt2(addpt2(t.p0, addpt2(t.p1, t.p2)), 3); +} + +/* + * based on the implementation from: + * + * Dmitry V. Sokolov, “Tiny Renderer: Lesson 2”, + * https://github.com/ssloy/tinyrenderer/wiki/Lesson-2:-Triangle-rasterization-and-back-face-culling + */ +Point3 +barycoords(Triangle2 t, Point2 p) +{ + Point2 p0p1 = subpt2(t.p1, t.p0); + Point2 p0p2 = subpt2(t.p2, t.p0); + Point2 pp0 = subpt2(t.p0, p); + + Point3 v = crossvec3(Vec3(p0p2.x, p0p1.x, pp0.x), Vec3(p0p2.y, p0p1.y, pp0.y)); + + /* handle degenerate triangles—i.e. the ones where every point lies on the same line */ + if(fabs(v.z) < 1) + return Pt3(-1,-1,-1,1); + return Pt3(1 - (v.x + v.y)/v.z, v.y/v.z, v.x/v.z, 1); +} + +/* 3D */ + Point3 -centroid(Triangle3 t) +centroid3(Triangle3 t) { return divpt3(addpt3(t.p0, addpt3(t.p1, t.p2)), 3); } |