set filename,width,height and drift from the command line

Signed-off-by: Jeff Carr <jcarr@wit.com>

community/seascape-shader/Makefile

@@ -0,0 +1,18 @@
+# go get -u github.com/faiface/pixel-examples
+# cd ~/go/src/github.com/faiface/pixel-examples/community/seascape-shader
+
+all:
+	go build
+	./seascape-shader
+
+push:
+	git pull
+	git add --all
+	-git commit -a -s
+	git push
+
+update:
+	git pull
+
+diff:
+	git diff

community/seascape-shader/README.md

@@ -8,6 +8,15 @@ Looking at the seascape.glsl example you can see **iResolution**, **iTime** and
 
 These are commonly needed to be exposed because these things are coming from outside and needs to be updated. Any other variable you need to have changed/updated from code can be exposed like those.
 
+## Command line arguments
+
+```
+./seascape-shader -h   # will show you the command line options
+
+./seascape-shader -filename ./shaders/seascape.glsl    # Seascape
+./seascape-shader -filename ./shaders/planetfall.glsl  # Planet Fall demo
+```
+
 ## Exposing variables
 
 How to expose variables like this?

community/seascape-shader/seascape.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"time"
+	"log"
 
 	"github.com/go-gl/mathgl/mgl32"
 
@@ -10,11 +11,25 @@ import (
 	"golang.org/x/image/colornames"
 )
 
+import "flag"
+import "os"
+
+var (
+	version       string
+	race          bool
+	debug         = os.Getenv("BUILDDEBUG") != ""
+	filename      string
+	width         int
+	height        int
+	timeout       = "120s"
+	uDrift        float32
+)
+
 func run() {
 	// Set up window configs
 	cfg := pixelgl.WindowConfig{ // Default: 1024 x 768
-		Title:  "Golang Seascape from Shadertoy",
-		Bounds: pixel.R(0, 0, 1024, 768),
+		Title:  "Golang GLSL",
+		Bounds: pixel.R(0, 0, float64(width), float64(height)),
 		VSync:  true,
 	}
 
@@ -30,8 +45,9 @@ func run() {
 
 	// I am putting all shader example initializing stuff here for
 	// easier reference to those learning to use this functionality
-	fragSource, err := LoadFileToString("shaders/seascape.glsl")
-	// fragSource, err := LoadFileToString("shaders/planetfall.glsl")
+
+	fragSource, err := LoadFileToString(filename)
+
 	if err != nil {
 		panic(err)
 	}
@@ -46,6 +62,7 @@ func run() {
 		"uResolution", &uResolution,
 		"uTime", &uTime,
 		"uMouse", &uMouse,
+		"uDrift", &uDrift,
 	)
 
 	canvas.SetFragmentShader(fragSource)
@@ -69,6 +86,27 @@ func run() {
 
 }
 
+func parseFlags() {
+	flag.StringVar  (&version,       "version",       "v0.1",                     "Set compiled in version string")
+	flag.StringVar  (&filename,      "filename",      "shaders/seascape.glsl",    "path to GLSL file")
+	flag.IntVar     (&width,         "width",         1024,                       "Width of the OpenGL Window")
+	flag.IntVar     (&height,        "height",        768,                        "Height of the OpenGL Window")
+	var tmp float64
+	flag.Float64Var (&tmp,           "drift",         0.01,                       "Speed of the gradual camera drift")
+	flag.BoolVar    (&race,          "race",          race,                       "Use race detector")
+
+	// this parses the arguements
+	flag.Parse()
+
+	uDrift = float32(tmp)
+	log.Println("width=",width)
+	log.Println("height=",height)
+	log.Println("uDrift=",uDrift)
+
+}
+
 func main() {
+	parseFlags()
+
 	pixelgl.Run(run)
 }

community/seascape-shader/shaders/seascape.glsl

@@ -10,6 +10,9 @@ uniform vec2 uResolution;
 uniform float uTime;
 uniform vec4 uMouse;
 
+// This is how much you are drifting around. Zero means it only moves when the mouse moves
+uniform float uDrift;
+
 out vec4 fragColor;
 
 const int NUM_STEPS = 8;
@@ -167,7 +170,7 @@ void main()
 	vec2 uv = gl_FragCoord.xy / uResolution.xy;
     uv = uv * 2.0 - 1.0;
     uv.x *= uResolution.x / uResolution.y;
-    float time = uTime * 0.3 + uMouse.x*0.01;
+    float time = uTime * uDrift * 5 + uMouse.x*0.01;
 
     // ray
     vec3 ang = vec3(sin(time*3.0)*0.1,sin(time)*0.2+0.3,time);