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authorrodri <rgl@antares-labs.eu>2020-06-29 18:28:02 +0000
committerrodri <rgl@antares-labs.eu>2020-06-29 18:28:02 +0000
commit6477319da461ad78a120a3c777228eaa8194c9f8 (patch)
treec009fc9bc5a868532d38d3518385e441529b0b2c /triangle.c
parent3857a7ad606f4f050411d27fc94116731fddb1b3 (diff)
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bring flat triangle rasterization back, with some goodies for future shading work. add uv coordinates to the vertex.
Diffstat (limited to 'triangle.c')
-rw-r--r--triangle.c72
1 files changed, 72 insertions, 0 deletions
diff --git a/triangle.c b/triangle.c
new file mode 100644
index 0000000..843ff6a
--- /dev/null
+++ b/triangle.c
@@ -0,0 +1,72 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <geometry.h>
+#include <graphics.h>
+
+/*
+ * comparison of a point p with an edge [e0 e1]
+ * p to the right: +
+ * p to the left: -
+ * p on the edge: 0
+ */
+static int
+edgeptcmp(Point e0, Point e1, Point p)
+{
+ Point3 e0p, e01, r;
+
+ p = subpt(p, e0);
+ e1 = subpt(e1, e0);
+ e0p = Vec3(p.x,p.y,0);
+ e01 = Vec3(e1.x,e1.y,0);
+ r = crossvec3(e0p, e01);
+
+ /* clamp to avoid overflow */
+ return fclamp(r.z, -1, 1); /* e0.x*e1.y - e0.y*e1.x */
+}
+
+Triangle
+Trian(int x0, int y0, int x1, int y1, int x2, int y2)
+{
+ return (Triangle){Pt(x0, y0), Pt(x1, y1), Pt(x2, y2)};
+}
+
+Triangle
+Trianpt(Point p0, Point p1, Point p2)
+{
+ return (Triangle){p0, p1, p2};
+};
+
+void
+triangle(Image *dst, Triangle t, int thick, Image *src, Point sp)
+{
+ Point pl[4];
+
+ pl[0] = t.p0;
+ pl[1] = t.p1;
+ pl[2] = t.p2;
+ pl[3] = pl[0];
+
+ poly(dst, pl, nelem(pl), 0, 0, thick, src, sp);
+}
+
+void
+filltriangle(Image *dst, Triangle t, Image *src, Point sp)
+{
+ Point pl[3];
+
+ pl[0] = t.p0;
+ pl[1] = t.p1;
+ pl[2] = t.p2;
+
+ fillpoly(dst, pl, nelem(pl), 0, src, sp);
+}
+
+int
+ptintriangle(Point p, Triangle t)
+{
+ /* counter-clockwise check */
+ return edgeptcmp(t.p0, t.p2, p) <= 0 &&
+ edgeptcmp(t.p2, t.p1, p) <= 0 &&
+ edgeptcmp(t.p1, t.p0, p) <= 0;
+}