new toy: barycentric.

1 files changed, 264 insertions, 0 deletions

diff --git a/barycentric.c b/barycentric.c
new file mode 100644
index 0000000..a72c2bf
--- /dev/null
+++ b/barycentric.c
@@ -0,0 +1,264 @@
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+#include <draw.h>
+#include <mouse.h>
+#include <keyboard.h>
+#include <geometry.h>
+
+enum {
+	PCBg,
+	PCFg,
+	PCPoly,
+	PCPolydark,
+	PCAux,
+	NCOLORS
+};
+
+typedef struct Polygon Polygon;
+
+struct Polygon
+{
+	Point2 *pts;
+	Point *scrpts;
+	int npts;
+
+	void (*push)(Polygon*, Point2);
+};
+
+Rectangle UR = {0,0,1,1};	/* unit rectangle */
+RFrame worldrf;
+Image *pal[NCOLORS];
+Polygon *thepoly;
+Point2 thepoint;
+
+void resized(void);
+Point toscreen(Point2);
+
+void
+polygonpush(Polygon *poly, Point2 p)
+{
+	poly->pts = realloc(poly->pts, ++poly->npts*sizeof(Point2));
+	poly->pts[poly->npts-1] = p;
+	poly->scrpts = realloc(poly->scrpts, (poly->npts+1)*sizeof(Point));
+	poly->scrpts[poly->npts-1] = toscreen(p);
+	poly->scrpts[poly->npts] = poly->scrpts[0]; /* close the polygon */
+}
+
+Polygon*
+newpolygon(Point2 *pts, int npts)
+{
+	Polygon *poly;
+	int i;
+
+	poly = malloc(sizeof(Polygon));
+	if(pts == nil){
+		poly->pts = nil;
+		poly->scrpts = nil;
+		poly->npts = 0;
+	}else{
+		poly->pts = pts;
+		poly->scrpts = malloc((npts+1)*sizeof(Point));
+		for(i = 0; i < npts; i++)
+			poly->scrpts[i] = toscreen(poly->pts[i]);
+		poly->scrpts[npts] = poly->scrpts[0]; /* close the polygon */
+		poly->npts = npts;
+	}
+	poly->push = polygonpush;
+	return poly;
+}
+
+void
+delpolygon(Polygon *poly)
+{
+	poly->push = nil;
+	poly->npts = 0;
+	free(poly->scrpts);
+	free(poly->pts);
+	free(poly);
+}
+
+Point
+toscreen(Point2 p)
+{
+	p = invrframexform(p, worldrf);
+	return Pt(p.x,p.y);
+}
+
+Point2
+fromscreen(Point p)
+{
+	return rframexform(Pt2(p.x,p.y,1), worldrf);
+}
+
+void
+initpalette(void)
+{
+	pal[PCBg] = allocimage(display, UR, screen->chan, 1, DWhite);
+	pal[PCFg] = allocimage(display, UR, screen->chan, 1, DBlack);
+	pal[PCPoly] = allocimage(display, UR, screen->chan, 1, DPalebluegreen);
+	pal[PCPolydark] = allocimage(display, UR, screen->chan, 1, DDarkblue);
+	pal[PCAux] = allocimage(display, UR, screen->chan, 1, DRed);
+}
+
+void
+drawinfo(void)
+{
+	Triangle2 t;
+	Point3 barypt;
+	Point2 *nextv, *prevv, in0, in1, labelpt;
+	char buf[128];
+	int i;
+
+	if(thepoly->npts < 3)
+		return;
+
+	t.p0 = thepoly->pts[0];
+	t.p1 = thepoly->pts[1];
+	t.p2 = thepoly->pts[2];
+	barypt = barycoords(t, thepoint);
+
+	snprint(buf, sizeof buf, "homo %v", thepoint);
+	string(screen, toscreen(Pt2(Dx(screen->r)/2 - strlen(buf)/2*font->width,10,1)), pal[PCFg], ZP, font, buf);
+
+	snprint(buf, sizeof buf, "bary %V", barypt);
+	string(screen, toscreen(Pt2(Dx(screen->r)/2 - strlen(buf)/2*font->width,10+font->height+2,1)), pal[PCFg], ZP, font, buf);
+
+	/* paint the vertex labels so that they are always visible */
+	for(i = 0; i < thepoly->npts; i++){
+		prevv = &thepoly->pts[(i-1+thepoly->npts) % thepoly->npts];
+		nextv = &thepoly->pts[(i+1+thepoly->npts) % thepoly->npts];
+		in0 = normvec2(subpt2(thepoly->pts[i], *prevv));
+		in1 = normvec2(subpt2(thepoly->pts[i], *nextv));
+		labelpt = addpt2(thepoly->pts[i], mulpt2(lerp2(in0, in1, 0.5), 30));
+
+		snprint(buf, sizeof buf, "p%d", i);
+		string(screen, toscreen(labelpt), pal[PCFg], ZP, font, buf);
+	}
+}
+
+void
+redraw(void)
+{
+	int i;
+
+	lockdisplay(display);
+	draw(screen, screen->r, pal[PCBg], nil, ZP);
+	fillpoly(screen, thepoly->scrpts, thepoly->npts, 1, pal[PCPoly], ZP);
+	poly(screen, thepoly->scrpts, thepoly->npts > 0? thepoly->npts+1: 0, Enddisc, Enddisc, 1, pal[PCPolydark], ZP);
+	for(i = 0; thepoly->npts > 0 && i < thepoly->npts+1; i++)
+		fillellipse(screen, thepoly->scrpts[i], 2, 2, pal[PCPolydark], ZP);
+	fillellipse(screen, toscreen(thepoint), 2, 2, pal[PCAux], ZP);
+	drawinfo();
+	flushimage(display, 1);
+	unlockdisplay(display);
+}
+
+void
+rmb(Mousectl *mc)
+{
+	thepoint = fromscreen(mc->xy);
+}
+
+void
+lmb(Mousectl *mc)
+{
+	if(thepoly->npts == 3){
+		delpolygon(thepoly);
+		thepoly = newpolygon(nil, 0);
+	}
+	thepoly->push(thepoly, fromscreen(mc->xy));
+}
+
+void
+mouse(Mousectl *mc)
+{
+	if((mc->buttons&1) != 0)
+		lmb(mc);
+	if((mc->buttons&4) != 0)
+		rmb(mc);
+}
+
+void
+key(Rune r)
+{
+	switch(r){
+	case Kdel:
+	case 'q':
+		threadexitsall(nil);
+	}
+}
+
+void
+usage(void)
+{
+	fprint(2, "usage: %s\n", argv0);
+	exits("usage");
+}
+
+void
+threadmain(int argc, char *argv[])
+{
+	Mousectl *mc;
+	Keyboardctl *kc;
+	Rune r;
+
+	GEOMfmtinstall();
+	ARGBEGIN{
+	default: usage();
+	}ARGEND;
+	if(argc > 0)
+		usage();
+
+	if(initdraw(nil, nil, nil) < 0)
+		sysfatal("initdraw: %r");
+	if((mc = initmouse(nil, screen)) == nil)
+		sysfatal("initmouse: %r");
+	if((kc = initkeyboard(nil)) == nil)
+		sysfatal("initkeyboard: %r");
+	initpalette();
+
+	worldrf.p = Pt2(screen->r.min.x,screen->r.min.y,1);
+	worldrf.bx = Vec2(1,0);
+	worldrf.by = Vec2(0,1);
+	thepoly = newpolygon(nil, 0);
+
+	display->locking = 1;
+	unlockdisplay(display);
+	redraw();
+
+	for(;;){
+		enum { MOUSE, RESIZE, KEYBOARD };
+		Alt a[] = {
+			{mc->c, &mc->Mouse, CHANRCV},
+			{mc->resizec, nil, CHANRCV},
+			{kc->c, &r, CHANRCV},
+			{nil, nil, CHANEND}
+		};
+
+		switch(alt(a)){
+		case MOUSE:
+			mouse(mc);
+			break;
+		case RESIZE:
+			resized();
+			break;
+		case KEYBOARD:
+			key(r);
+			break;
+		}
+
+		redraw();
+	}
+}
+
+void
+resized(void)
+{
+	lockdisplay(display);
+	if(getwindow(display, Refnone) < 0)
+		sysfatal("couldn't resize");
+	unlockdisplay(display);
+	worldrf.p = Pt2(screen->r.min.x,screen->r.min.y,1);
+	redraw();
+}