Merge pull request #40 from johncohn/feature/substeps-flag

Add -substeps: trade solver accuracy for CPU headroom on slower hardware

Author: crgimenes

main.go

@@ -30,8 +30,14 @@ func main() {
 	scenePath := flag.String("scene", "", "path to an .afoil scene file to load at startup instead of the interactive default foil")
 	fullscreen := flag.Bool("fullscreen", false, "start in full screen")
 	hideControls := flag.Bool("hidecontrols", false, "hide every panel and control, showing only the flow image (kiosk mode)")
+	substepsFlag := flag.Int("substeps", substeps, "solver steps per displayed frame; lower this on slower hardware to trade physical accuracy for CPU headroom")
 	flag.Parse()
 
+	if *substepsFlag < 1 {
+		log.Fatalf("kutta: -substeps %d: must be at least 1", *substepsFlag)
+	}
+	substeps = *substepsFlag
+
 	ebiten.SetWindowSize(winW, winH)
 	ebiten.SetWindowTitle(windowTitle)
 	ebiten.SetWindowResizingMode(ebiten.WindowResizingModeEnabled)

substeps_js.go

@@ -12,4 +12,7 @@ package main
 // The trade is that the flow evolves slower in wall-clock time than on the
 // desktop. Smooth and slow reads better than fast and juddering, and the
 // physics per step is identical either way.
-const substeps = 1
+//
+// It's a var, not a const, so the same -substeps flag in main.go that
+// overrides the native default can override this one too.
+var substeps = 1

substeps_other.go

@@ -5,4 +5,8 @@ package main
 // substeps is how many solver steps advance per displayed frame. A native build
 // runs a step in about 2.3 ms on this grid, so three of them fit inside a 60 Hz
 // frame with room left for the smoke, the field and the panels.
-const substeps = 3
+//
+// It's a var, not a const: the -substeps flag in main.go overrides it, to
+// trade physical accuracy/responsiveness for CPU headroom on slower hardware
+// (e.g. a Raspberry Pi) without a rebuild.
+var substeps = 3