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author | rodri <rgl@antares-labs.eu> | 2023-01-28 15:33:17 +0000 |
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committer | rodri <rgl@antares-labs.eu> | 2023-01-28 15:33:17 +0000 |
commit | 302a41f84da0884d1ac07d653868c7d0e7604362 (patch) | |
tree | 40e46d21437f9eb9bf38d2915185b8420c8c8112 /triangle.c | |
parent | fdeaa2423c582df8d9e9ae6b0e26d386b5531262 (diff) | |
download | libgeometry-302a41f84da0884d1ac07d653868c7d0e7604362.tar.gz libgeometry-302a41f84da0884d1ac07d653868c7d0e7604362.tar.bz2 libgeometry-302a41f84da0884d1ac07d653868c7d0e7604362.zip |
made edgeptcmp public. implemented centroid for Triangle[23], and a homogeneous-to-barycentric coordinates conversion function for Triangle2.
Diffstat (limited to 'triangle.c')
-rw-r--r-- | triangle.c | 33 |
1 files changed, 32 insertions, 1 deletions
@@ -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); } |