X-Git-Url: https://jasonwoof.com/gitweb/?p=vor.git;a=blobdiff_plain;f=dust.c;h=96a5805601b5d99841e5fed771f1e57530ff97e7;hp=b336696035da9c1cbd7248114d023487d600e551;hb=1796973cc22433f9b875b8b6d945fc914a78e14d;hpb=badd0f9bfc6dad829073e606c1953572ece1b06b

diff --git a/dust.c b/dust.c
index b336696..96a5805 100644
--- a/dust.c
+++ b/dust.c
@@ -13,6 +13,9 @@ struct dust_mote {
 
 struct dust_mote motes[N_DUST_MOTES];
 
+// lower bound to ensure that we don't lose precision when wrapping.
+static float zero;
+
 void
 init_dust(void)
 {
@@ -24,21 +27,25 @@ init_dust(void)
 		b = (MAX_DUST_DEPTH - motes[i].z) * 255.0 / MAX_DUST_DEPTH;
 		motes[i].color = SDL_MapRGB(surf_screen->format, b, b, b);
 	}
+
+	zero = pow(-10, ceil(log10(XSIZE)) - FLT_DIG);
 }
 
 void
-move_dust(void)
+move_dust(float ticks)
 {
 	int i;
-	float xscroll = screendx * t_frame;
-	float yscroll = screendy * t_frame;
+	float xscroll = screendx * ticks;
+	float yscroll = screendy * ticks;
+	
 	for(i=0; i<N_DUST_MOTES; i++) {
 		motes[i].x -= xscroll / (1.3 + motes[i].z);
-		motes[i].y -= yscroll / (1.3 + motes[i].z);
 		if(motes[i].x >= XSIZE) motes[i].x -= XSIZE;
-		else if(motes[i].x < 0) motes[i].x += XSIZE;
+		else if(motes[i].x < zero) motes[i].x += XSIZE;
+
+		motes[i].y -= yscroll / (1.3 + motes[i].z);
 		if(motes[i].y >= YSIZE) motes[i].y -= YSIZE;
-		else if(motes[i].y < 0) motes[i].y += YSIZE;
+		else if(motes[i].y < zero) motes[i].y += YSIZE;
 	}
 }