shithub: ballistics

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make the scale adjustable. add knobs for most parameters.

--- a/dat.h

+++ b/dat.h

@@ -1,7 +1,6 @@

 #define Eg	9.81	/* earth's gravity (m·s⁻²) */

 #define Cd	0.45	/* drag coefficient for a sphere */

 #define ρ	1.293	/* air density (kg·m⁻³) */

-#define PIX2M	0.001

 #define M2PIX	(1.0/PIX2M)

 enum {

@@ -11,6 +10,7 @@

 	Sdrag,

 	Sdeltax,

 	Seta,

+	Sscale,

 	SLEN,

 };

--- a/main.c

+++ b/main.c

@@ -8,6 +8,8 @@

 #include "dat.h"

 #include "fns.h"

+double PIX2M = 5;

+

 Mousectl *mc;

 Keyboardctl *kc;

 Channel *scrsync;

@@ -56,7 +58,7 @@

 	ball.v = addpt2(ball.v, mulpt2(addpt2(Vec2(0,-Eg), divpt2(Fd, ball.mass)), Δt));

 	ball.p = addpt2(ball.p, mulpt2(ball.v, Δt));

 	snprint(stats[Spos], sizeof(stats[Spos]), "p: %v", ball.p);

-	snprint(stats[Sdrag], sizeof(stats[Sdrag]), "Fd: %v", Fd);

+	snprint(stats[Sdrag], sizeof(stats[Sdrag]), "Fd: %v", divpt2(Fd, ball.mass));

 	if(ball.p.y <= (2+1)*M2PIX){

 		ball.p.y = (2+1)*M2PIX;

 		ball.v = Vec2(0,0);

@@ -91,21 +93,49 @@

 {

 	enum {

 		SETV0,

+		SETPOS,

+		SETMASS,

+		SETDIAM,

 	};

 	static char *items[] = {

 	 [SETV0]	"set v0",

+	 [SETPOS]	"set position",

+	 [SETMASS]	"set mass",

+	 [SETDIAM]	"set diameter",

 		nil

 	};

 	static Menu menu = { .item = items };

-	char buf[32];

+	char buf[32], *p;

-	snprint(buf, sizeof(buf), "%g", v0);

 	switch(menuhit(2, mc, &menu, nil)){

 	case SETV0:

+		snprint(buf, sizeof(buf), "%g", v0);

 		enter("v0(m/s):", buf, sizeof(buf), mc, kc, nil);

 		if(buf[0] != 0)

 			v0 = strtod(buf, nil);

 		break;

+	case SETPOS:

+		snprint(buf, sizeof(buf), "%g, %g", ball.p.x, ball.p.y);

+		enter("pos(x,y):", buf, sizeof(buf), mc, kc, nil);

+		if(buf[0] != 0 && (p = strchr(buf, ',')) != nil){

+			ball.p.x = strtod(buf, nil);

+			ball.p.y = strtod(p+1, nil);

+		}

+		break;

+	case SETMASS:

+		snprint(buf, sizeof(buf), "%g", ball.mass);

+		enter("mass(kg):", buf, sizeof(buf), mc, kc, nil);

+		if(buf[0] != 0)

+			ball.mass = strtod(buf, nil);

+		break;

+	case SETDIAM:

+		snprint(buf, sizeof(buf), "%g", 2*ball.r);

+		enter("diameter(m):", buf, sizeof(buf), mc, kc, nil);

+		if(buf[0] != 0){

+			ball.r = strtod(buf, nil)/2;

+			A = 2*PI*ball.r*ball.r;	/* ½(4πr²) */

+		}

+		break;

 	}

 }

@@ -134,6 +164,24 @@

 }

 void

+zoomin(void)

+{

+	PIX2M += 0.01;

+	worldrf.bx = Vec2(PIX2M,0);

+	worldrf.by = Vec2(0,-PIX2M);

+	snprint(stats[Sscale], sizeof(stats[Sscale]), "s: %gm/pix", M2PIX);

+}

+

+void

+zoomout(void)

+{

+	PIX2M -= 0.01;

+	worldrf.bx = Vec2(PIX2M,0);

+	worldrf.by = Vec2(0,-PIX2M);

+	snprint(stats[Sscale], sizeof(stats[Sscale]), "s: %gm/px", M2PIX);

+}

+

+void

 mouse(void)

 {

 	Point2 p;

@@ -154,6 +202,10 @@

 		mmb();

 	if((mc->buttons & 4) != 0)

 		rmb();

+	if((mc->buttons & 8) != 0)

+		zoomin();

+	if((mc->buttons & 16) != 0)

+		zoomout();

 }

 void

@@ -215,6 +267,8 @@

 	if(statc == nil)

 		sysfatal("allocimage: %r");

+	snprint(stats[Sscale], sizeof(stats[Sscale]), "s: %gm/pix", M2PIX);

+

 	worldrf.p = Pt2(screen->r.min.x, screen->r.max.y, 1);

 	worldrf.bx = Vec2(PIX2M,0);

 	worldrf.by = Vec2(0,-PIX2M);

@@ -221,10 +275,10 @@

 	ball.p = Pt2((2+1)*M2PIX,(2+1)*M2PIX,1);

 	ball.v = Vec2(0, 0);

-	ball.mass = 106000;

-	ball.r = 0.1;		/* 10cm */

+	ball.mass = 0.149;

+	ball.r = 0.375;		/* 3.75cm */

 	A = 2*PI*ball.r*ball.r;	/* ½(4πr²) */

-	v0 = 1640; /* Paris Gun's specs */

+	v0 = 53.64;		/* avg baseball hit speed */

 	scrsync = chancreate(1, 0);

 	display->locking = 1;