From 0e3577d6fe5ac6748481abbc701d520b0cb64c2b Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Wed, 28 Aug 2019 00:12:10 -0400
Subject: [PATCH] gr-sim: looking at some plasma

---
 gr-sim/plasma/Makefile | 21 +++++++++++++
 gr-sim/plasma/plasma.c | 70 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)
 create mode 100644 gr-sim/plasma/Makefile
 create mode 100644 gr-sim/plasma/plasma.c

diff --git a/gr-sim/plasma/Makefile b/gr-sim/plasma/Makefile
new file mode 100644
index 00000000..f1a139e2
--- /dev/null
+++ b/gr-sim/plasma/Makefile
@@ -0,0 +1,21 @@
+CC = gcc
+CFLAGS = -Wall -O2 -I.. -g
+LFLAGS = -lm
+
+SDL_LIBS= `sdl-config --libs`
+SDL_INCLUDE= `sdl-config --cflags`
+GR_SIM = ../gr-sim.a
+
+all:	plasma
+
+
+plasma:	plasma.o $(GR_SIM)
+	$(CC) $(LFLAGS) $(SDL_LIBS) -o plasma plasma.o \
+		$(GR_SIM)
+
+plasma.o:	plasma.c
+	$(CC) $(CFLAGS) -c plasma.c
+
+
+clean:	
+	rm -f *~ *.o plasma
diff --git a/gr-sim/plasma/plasma.c b/gr-sim/plasma/plasma.c
new file mode 100644
index 00000000..c7c52488
--- /dev/null
+++ b/gr-sim/plasma/plasma.c
@@ -0,0 +1,70 @@
+/* for demoscene, you need a plasma effect... */
+/* https://rosettacode.org/wiki/Plasma_effect */
+/* https://www.bidouille.org/prog/plasma */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <math.h>
+
+#include "tfv_zp.h"
+#include "gr-sim.h"
+
+#define pi 3.14159265358979323846264338327950
+
+
+unsigned char colors[]={15,13,9,1,8,5,0,0};
+
+
+int main(int argc, char **argv) {
+
+	int ch,xx,yy,sec=128;
+	double dx,dy,dv,r;
+
+	grsim_init();
+
+	gr();
+	clear_screens();
+
+	color_equals(15);
+	hlin(0,0,40,39);
+
+	ram[DRAW_PAGE]=0x0;
+
+	while(1) {
+
+		sec++;
+
+		for(yy=0;yy<40;yy++) {
+			for(xx=0;xx<40;xx++) {
+
+//				dx = xx + .5 * sin(sec/5.0);
+				dx = sin(xx+sec);
+				dy = yy + .5 * cos(sec/3.0);
+				dv = sin(xx*10 + sec) +
+					sin(10*(xx*sin(sec/2.0) +
+					yy*cos(sec/3.0)) + sec) +
+					sin(sqrt(100*(dx*dx + dy*dy)+1) + sec);
+				r=fabs(sin(dv*pi))*16;
+			printf("%d %d %f %f %f %f\n",xx,yy,dx,dy,dv,r);
+//			setcolor(COLOR(255*fabs(sin(dv*pi)),255*fabs(sin(dv*pi + 2*pi/3)),255*fabs(sin(dv*pi + 4*pi/3))));
+
+
+
+				color_equals(fabs(dx)*16);
+				plot(xx,yy);
+				//plot(xx-r+2,yy);
+//				printf("plot %d,%d = %d\n",xx,yy,colors[col]);
+			}
+
+		}
+
+		grsim_update();
+		ch=grsim_input();
+		if (ch=='q') exit(0);
+		usleep(20000);
+
+	}
+
+	return 0;
+}