From 96cd7ac13106f65d309538672376a3cc6617753e Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Thu, 28 Dec 2017 13:17:16 -0500
Subject: [PATCH] mode7: more work on starfield

---
 gr-sim/starfield.c | 133 +++++++++++++++++++++++++++++++++++++--------
 1 file changed, 110 insertions(+), 23 deletions(-)

diff --git a/gr-sim/starfield.c b/gr-sim/starfield.c
index bc05a6de..28b3d647 100644
--- a/gr-sim/starfield.c
+++ b/gr-sim/starfield.c
@@ -4,59 +4,146 @@
 
 #include "gr-sim.h"
 
-#define NUMSTARS	64
+#define NUMSTARS	16
+
+struct fixed_type {
+	char i;
+	unsigned char f;
+};
+
 
 struct star_type {
-	double x;
-	double y;
-	double z;
+	struct fixed_type x;
+	struct fixed_type y;
+	struct fixed_type z;
+	int color;
 };
 
+static void double_to_fixed(double d, struct fixed_type *f) {
+
+        int temp;
+
+        temp=d*256;
+
+        f->i=(temp>>8)&0xff;
+
+        f->f=temp&0xff;
+
+
+}
+
+static void print_fixed(struct fixed_type *f) {
+
+        printf("%02X.%02X",f->i,f->f);
+}
+
+static void fixed_add(struct fixed_type *x, struct fixed_type *y, struct fixed_type *z) {
+        int carry;
+        short sum;
+
+        sum=(short)(x->f)+(short)(y->f);
+
+        if (sum>=256) carry=1;
+        else carry=0;
+
+        z->f=sum&0xff;
+
+        z->i=x->i+y->i+carry;
+}
+
+static double fixed_to_double(struct fixed_type *f) {
+
+	double d;
+
+        d=f->i;
+        d+=((double)(f->f))/256.0;
+
+//      printf("(%02x.%02x)=%lf\n",f->i,f->f,*d);
+
+	return d;
+}
+
+
 static struct star_type stars[NUMSTARS];
 
 int main(int argc, char **argv) {
 
 	int ch,i;
 
-	int spreadx=40;
-	int spready=40;
-	int spreadz=5;
+	int spreadx=256;
+	int spready=256;
+	int spreadz=16;
+	struct fixed_type speedz;
+
+	double_to_fixed(-0.25,&speedz);
 
 	grsim_init();
 
 	for(i=0;i<NUMSTARS;i++) {
-		stars[i].x=(drand48()-0.5)*spreadx;
-		stars[i].y=(drand48()-0.5)*spready;
-		stars[i].z=((drand48())*spreadz)+0.1;
-		printf("%.2lf,%2lf,%.2lf\n",stars[i].x,stars[i].y,stars[i].z);
+		double_to_fixed( (drand48()-0.5)*spreadx,&stars[i].x);
+		double_to_fixed( (drand48()-0.5)*spready,&stars[i].y);
+		double_to_fixed( ((drand48())*spreadz)+0.1,&stars[i].z);
+		print_fixed(&stars[i].x);
+		printf(",");
+		print_fixed(&stars[i].y);
+		printf(",");
+		print_fixed(&stars[i].z);
+		printf("\n");
 	}
 	gr();
 
-
 	while(1) {
 		gr();
 
+		/* Set color */
 		for(i=0;i<NUMSTARS;i++) {
-			if (stars[i].z<2) color_equals(15);
-			else if (stars[i].z<3) color_equals(7);
-			else color_equals(5);
-			basic_plot(stars[i].x/stars[i].z+20,
-					stars[i].y/stars[i].z+20);
+			if (stars[i].z.i<(spreadz/3)) stars[i].color=15;
+			else if (stars[i].z.i<(spreadz*2/3)) stars[i].color=13;
+			else stars[i].color=5;
+
 		}
 
+		/* draw stars */
 		for(i=0;i<NUMSTARS;i++) {
-			stars[i].z+=-0.125;
-			if (stars[i].z<0) {
-				stars[i].x=(drand48()-0.5)*spreadx;
-				stars[i].y=(drand48()-0.5)*spready;
-				stars[i].z=((drand48())*spreadz)+0.1;
+			int tempx,tempy;
+			double dx,dy;
+
+			dx=fixed_to_double(&stars[i].x)/
+				fixed_to_double(&stars[i].z);
+
+			tempx=dx+20;
+
+			dy=fixed_to_double(&stars[i].y)/
+				fixed_to_double(&stars[i].z);
+
+			tempy=dy+20;
+
+			if ((tempx<0) || (tempy<0) || (tempx>=40) ||
+				(tempy>=40)) {
+
+				double_to_fixed((drand48()-0.5)*spreadx,
+					&stars[i].x);
+				double_to_fixed((drand48()-0.5)*spready,
+					&stars[i].y);
+				stars[i].z.i=spreadz;
+
 			}
+			else {
+				color_equals(stars[i].color);
+				basic_plot(tempx,tempy);
+			}
+
+		}
+
+		/* Move stars */
+		for(i=0;i<NUMSTARS;i++) {
+			fixed_add(&stars[i].z,&speedz,&stars[i].z);
 		}
 
 		grsim_update();
 		ch=grsim_input();
 		if (ch=='q') exit(0);
-		usleep(30000);
+		usleep(10000);
 	}
 
 	return 0;