shithub: tinyrend

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Lesson 0: Bresenham's Line Drawing Algorithm—Third attempt

--- a/main.c

+++ b/main.c

@@ -6,7 +6,7 @@

 #include <memdraw.h>

 #include <mouse.h>

 #include <keyboard.h>

-#include "libgeometry/geometry.h"

+#include <geometry.h>

 Memimage *fb;

@@ -91,19 +91,47 @@

 }

 void

+swap(int *a, int *b)

+{

+	int t;

+

+	t = *a;

+	*a = *b;

+	*b = t;

+}

+

+void

 bresenham(Memimage *dst, Point p0, Point p1, Memimage *src)

 {

-	double t, dt;

-	Point p;

+	int steep = 0;

+	double t;

+	Point p, dp;

-	dt = 0.01;

+	if(abs(p0.x-p1.x) < abs(p0.y-p1.y)){

+		steep = 1;

+		swap(&p0.x, &p0.y);

+		swap(&p1.x, &p1.y);

+	}

-	for(t = 0; t < 1; t += dt){

-		p = Pt(

-			flerp(p0.x, p1.x, t),

-			flerp(p0.y, p1.y, t)

-		);

+	/* make them left-to-right */

+	if(p0.x > p1.x){

+		swap(&p0.x, &p1.x);

+		swap(&p0.y, &p1.y);

+	}

+

+	dp = subpt(p1, p0);

+

+	for(p = p0; p.x <= p1.x; p.x++){

+		t = (double)(p.x-p0.x)/(p1.x-p0.x);

+		p.y = flerp(p0.y, p1.y, t);

+

+		if(steep)

+			swap(&p.x, &p.y);

+

 		pixel(dst, p, src);

+

+		if(steep)

+			swap(&p.x, &p.y);

 	}

 }

@@ -181,6 +209,8 @@

 	fb = eallocmemimage(screen->r, screen->chan);

 	red = rgb(DRed);

 	bresenham(fb, Pt(40,40), Pt(300,300), red);

+	bresenham(fb, Pt(80,80), Pt(100,200), red);

+	bresenham(fb, Pt(80,80), Pt(200,100), red);

 	display->locking = 1;

 	unlockdisplay(display);

--- a/mkfile

+++ b/mkfile

@@ -1,24 +1,8 @@

 </$objtype/mkfile

-BIN=/$objtype/bin/musw

+BIN=/$objtype/bin

 TARG=tinyrend

 OFILES=\

 	main.$O\

-HFILES=\

-	./libgeometry/geometry.h\

-

-LIB=\

-	./libgeometry/libgeometry.a$O\

-

-CFLAGS=$CFLAGS

-

 </sys/src/cmd/mkone

-

-./libgeometry/libgeometry.a$O:

-	cd ./libgeometry

-	mk install

-

-clean nuke:V:

-	rm -f *.[$OS] [$OS].??* $TARG

-	@{cd ./libgeometry; mk $target}