pulled out from my fork of upstream repo

.gitignore

@@ -0,0 +1,3 @@
+*.swp
+go.mod
+go.sum

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:
+	GO111MODULE=off go build
+	./seascape-shader
+
+push:
+	git pull
+	git add --all
+	-git commit -a -s
+	git push
+
+update:
+	git pull
+
+diff:
+	git diff

README.md

@@ -0,0 +1,133 @@
+# Shadertoy to Pixel shader conversion
+
+This will show you an example how you can take an example from [shadertoy.com](shadertoy.com) and use it with the Pixel Shader support.
+
+["Seascape" by Alexander Alekseev aka TDM - 2014](https://www.shadertoy.com/view/Ms2SD1) is a nice one. It's very impressive and doesn't use textures so that simplifies things for us. Let's try that one.
+
+Looking at the seascape.glsl example you can see **iResolution**, **iTime** and **iMouse** in there.
+
+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?
+
+Well, first we need to figure out what type of variables they are. Looking at the shader, you can see **iResolution.x** in there. This tells you that it's not a simple type. In this case it's a **vec2***, a **Vector containing 2 values, x and y**. This makes sense since resolution is described by x and y. That is, width and height.
+
+And thus, we create our variable in Go with like so:
+```
+uResolution := mgl32.Vec2{float32(win.Bounds().W()), float32(win.Bounds().H())}
+```
+That is, to be of the type **mgl32.Vec2**. Here we create it by taking the window's width and height.
+
+**iTime** is just a float, and thus that is just created like so:
+```
+var uTime float32
+```
+
+For the **iMouse**, it's a **mgl32.Vec4**, a **Vector containing 4 variables**. We only use x and y for the mouse position here though.
+```
+var uMouse mgl32.Vec4
+```
+
+And finally, to make our variables available in the shader itself we use:
+```
+canvas.SetUniform(name string, value interface{})
+```
+
+We create a handy function to do this:
+
+``` go
+func EasyBindUniforms(c *pixelgl.Canvas, unifs ...interface{}) {
+	if len(unifs)%2 != 0 {
+		panic("needs to be divisable by 2")
+	}
+	for i := 0; i < len(unifs); i += 2 {
+
+		c.SetUniform(unifs[i+0].(string), unifs[i+1])
+	}
+}
+```
+and we call that function like so:
+
+``` go
+	EasyBindUniforms(canvas,
+		"uResolution", &uResolution,
+		"uTime", &uTime,
+		"uMouse", &uMouse,
+	)
+```
+
+## Updating shader source file
+
+We also need to do some updates to the shader file itself to match these variables. First thing would be to add the variables we exposed in Go.
+
+```
+uniform vec2 uResolution;
+uniform float uTime;
+uniform vec4 uMouse;
+```
+Then we just rename the variables to match.
+
+We also need to rename the main function itself, as the one used here is specific for use with shadertoy. For our shader, the entrypoint is main(). So we rename:
+```
+void mainImage( out vec4 fragColor, in vec2 fragCoord )
+```
+to
+```
+void main() {
+```
+
+
+Also, rename:
+```
+fragCoord
+```
+to
+```
+gl_FragCoord
+```
+because this is available globaly in the OpenGL space for the shader.
+
+We also need to add:
+```
+out vec4 fragColor;
+```
+
+to expose that.
+
+Lastly, we need to add:
+```
+#version 330 core
+```
+at the top to tell what version we require.
+
+
+## Using shader
+To use the shader in our canvas we do:
+```
+canvas.SetFragmentShader(fragSource string)
+```
+where fragSource is the fragment shader, not a path fo a file.
+
+#
+
+## Result converting shadertoy shader to use with Pixel
+
+Here is a diff of the changes:
+
+![code changes](shader_diffs.png "Code changes")
+
+
+And that is it. Running the program we should see this:
+
+![seascape animation](seascape.gif "Seascape animation")

config.go

@@ -0,0 +1,79 @@
+package main
+
+/* 
+	This simply parses the command line arguments using the default golang
+	package called 'flag'. This can be used as a simple template to parse
+	command line arguments in other programs.
+
+	It puts everything in the 'config' package which I think is a good
+	wrapper around the 'flags' package and doesn't need a whole mess of
+	global variables
+*/
+
+import "log"
+import "os"
+import "flag"
+import "fmt"
+import "github.com/gookit/config"
+
+var customUsage = func() {
+	fmt.Fprintf(flag.CommandLine.Output(), "Usage of %s:\n", os.Args[0])
+	flag.PrintDefaults()
+
+	fmt.Println("")
+	fmt.Println("EXAMPLES:")
+	fmt.Println("")
+	fmt.Println(os.Args[0] + " --width 1024 --height 768 --drift .1 --filename shaders/seascape.glsl")
+	fmt.Println(os.Args[0] + " --width 640 --height 480 --filename shaders/planetfall.glsl")
+	fmt.Println("")
+}
+
+func parseFlags() {
+	var version       string
+	var race          bool
+	var filename      string
+	var width         int
+	var height        int
+	var glDrift       float64
+
+	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")
+
+	flag.Float64Var (&glDrift,       "drift",         0.01,                       "Speed of the gradual camera drift")
+	flag.BoolVar    (&race,          "race",          race,                       "Use race detector")
+
+	// Set the output if something fails to stdout rather than stderr
+	flag.CommandLine.SetOutput(os.Stdout)
+
+	flag.Usage = customUsage
+	flag.Parse()
+
+	if flag.Parsed() {
+		log.Println("flag.Parse() worked")
+	} else {
+		log.Println("flag.Parse() failed")
+	}
+
+	// keys := []string{"filename", "width", "height", "drift"}
+	// keys := []string{"width", "height", "drift"}
+
+//	keys := []string{"height"}
+//	config.LoadFlags(keys)
+
+	config.Set("width", width)
+	config.Set("height", height)
+	config.Set("glDrift", glDrift)
+	config.Set("filename", filename)
+}
+
+func parseConfig() {
+	config.WithOptions(config.ParseEnv)
+	parseFlags()
+
+	// config.LoadOSEnv([]string{"MAIL"})
+	// config.LoadOSEnv([]string{"USER"})
+	// config.LoadOSEnv([]string{"BUILDDEBUG"})
+}

planetfall.glsl

@@ -0,0 +1,333 @@
+// Created by inigo quilez - iq/2018
+// License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
+
+// Pretty much a modification to Klems' shader (https://www.shadertoy.com/view/XlcfRs)
+// Youtube version: https://www.youtube.com/watch?v=q1OBrqtl7Yo
+
+#version 330 core
+
+// Change AA to 1 if it renders too slow for you
+#define AA 1
+
+uniform vec2      uResolution;
+uniform float     uTime;                 // shader playback time (in seconds)
+uniform vec4      uMouse;
+
+// there is tearing on my box. is this because this isn't working? -- jcarr
+uniform int       iFrame;                // shader playback frame
+
+out vec4 fragColor;
+// in vec2 fragCoord;
+
+mat3 makeBase( in vec3 w )
+{
+	float k = inversesqrt(1.0-w.y*w.y);
+    return mat3( vec3(-w.z,0.0,w.x)*k, 
+                 vec3(-w.x*w.y,1.0-w.y*w.y,-w.y*w.z)*k,
+                 w);
+}
+
+#define ZERO (min(iFrame,0))
+
+// http://iquilezles.org/www/articles/intersectors/intersectors.htm
+vec2 sphIntersect( in vec3 ro, in vec3 rd, in float rad )
+{
+	float b = dot( ro, rd );
+	float c = dot( ro, ro ) - rad*rad;
+	float h = b*b - c;
+	if( h<0.0 ) return vec2(-1.0);
+    h = sqrt(h);
+	return vec2(-b-h,-b+h);
+}
+
+// http://iquilezles.org/www/articles/distfunctions/distfunctions.htm
+float sdCapsule( in vec3 p, in float b, in float r )
+{
+    float h = clamp( p.z/b, 0.0, 1.0 );
+    return length( p - vec3(0.0,0.0,b)*h ) - r;//*(0.2+1.6*h);
+}
+
+// modified Keinert et al's inverse Spherical Fibonacci Mapping
+vec4 inverseSF( in vec3 p, const in float n )
+{
+    const float PI = 3.14159265359;
+	const float PHI = 1.61803398875;
+
+    float phi = min(atan(p.y,p.x),PI);
+    float k   = max(floor(log(n*PI*sqrt(5.0)*(1.-p.z*p.z))/log(PHI+1.)),2.0);
+    float Fk  = pow(PHI,k)/sqrt(5.0);
+    vec2  F   = vec2(round(Fk),round(Fk*PHI));
+    vec2  G   = PI*(fract((F+1.0)*PHI)-(PHI-1.0));    
+    
+    mat2 iB = mat2(F.y,-F.x,G.y,-G.x)/(F.y*G.x-F.x*G.y);
+    vec2 c = floor(iB*0.5*vec2(phi,n*p.z-n+1.0));
+
+    float ma = 0.0;
+    vec4 res = vec4(0);
+    for( int s=0; s<4; s++ )
+    {
+        vec2 uv = vec2(s&1,s>>1);
+        float i = dot(F,uv+c);
+        float phi = 2.0*PI*fract(i*PHI);
+        float cT = 1.0 - (2.0*i+1.0)/n;
+        float sT = sqrt(1.0-cT*cT);
+        vec3 q = vec3(cos(phi)*sT, sin(phi)*sT,cT);
+        float a = dot(p,q);
+        if (a > ma)
+        {
+            ma = a;
+            res.xyz = q;
+            res.w = i;
+        }
+    }
+    return res;
+}
+
+float map( in vec3 p, out vec4 color, const in bool doColor )
+{
+    float lp = length(p);
+    float dmin = lp-1.0;
+    {
+    vec3 w = p/lp;
+    vec4 fibo = inverseSF(w, 700.0);
+    float hh = 1.0 - smoothstep(0.05,0.1,length(fibo.xyz-w));
+    dmin -= 0.07*hh;
+    color = vec4(0.05,0.1,0.1,1.0)*hh * (1.0+0.5*sin(fibo.w*111.1));
+    }
+    
+    
+    float s = 1.0;
+    
+    for( int i=0; i<3; i++ )
+    {
+        float h = float(i)/float(3-1);
+        
+        vec4 f = inverseSF(normalize(p), 65.0 + h*75.0);
+        
+        // snap
+        p -= f.xyz;
+
+        // orient to surface
+        p = p*makeBase(f.xyz);
+
+        // scale
+        float scale = 6.6 + 2.0*sin(111.0*f.w);
+        p *= scale;
+        p.xy *= 1.2;
+        
+        //translate
+        p.z -= 3.0 - length(p.xy)*0.6*sin(f.w*212.1);
+            
+        // measure distance
+        s *= scale;
+        float d = sdCapsule( p, -6.0, 0.42 );
+        d /= s;
+
+        if( d<dmin )
+        {
+            if( doColor )
+            {
+                color.w *= smoothstep(0.0, 5.0/s, dmin-d);
+
+                if( i==0 ) 
+                {
+                    color.xyz = vec3(0.425,0.36,0.1)*1.1;  // fall
+                  //color.xyz = vec3(0.4,0.8,0.1);         // summer
+                  //color.xyz = vec3(0.4,0.4,0.8);         // winter
+                }
+
+                color.zyx += 0.3*(1.0-sqrt(h))*sin(f.w*1111.0+vec3(0.0,1.0,2.0));
+                color.xyz = max(color.xyz,0.0);
+            }
+            dmin = d;
+        }
+        else
+        {
+          color.w *= 0.4*(0.1 + 0.9*smoothstep(0.0, 1.0/s, d-dmin));
+        }
+    }
+    
+    return dmin;
+}
+
+// http://iquilezles.org/www/articles/normalsSDF/normalsSDF.htm
+vec3 calcNormal( in vec3 pos, in float ep )
+{
+    vec4 kk;
+#if 0
+    vec2 e = vec2(1.0,-1.0)*0.5773;
+    return normalize( e.xyy*map( pos + e.xyy*ep, kk, false ) + 
+					  e.yyx*map( pos + e.yyx*ep, kk, false ) + 
+					  e.yxy*map( pos + e.yxy*ep, kk, false ) + 
+					  e.xxx*map( pos + e.xxx*ep, kk, false ) );
+#else
+    // prevent the compiler from inlining map() 4 times
+    vec3 n = vec3(0.0);
+    for( int i=ZERO; i<4; i++ )
+    {
+        vec3 e = 0.5773*(2.0*vec3((((i+3)>>1)&1),((i>>1)&1),(i&1))-1.0);
+        n += e*map(pos+e*ep, kk, false);
+    }
+    return normalize(n);
+#endif    
+    
+}
+
+// http://iquilezles.org/www/articles/rmshadows/rmshadows.htm
+float calcSoftshadow( in vec3 ro, in vec3 rd, float tmin, float tmax, const float k )
+{
+    vec2 bound = sphIntersect( ro, rd, 2.1 );
+    tmin = max(tmin,bound.x);
+    tmax = min(tmax,bound.y);
+    
+	float res = 1.0;
+    float t = tmin;
+    for( int i=0; i<50; i++ )
+    {
+    	vec4 kk;
+		float h = map( ro + rd*t, kk, false );
+        res = min( res, k*h/t );
+        t += clamp( h, 0.02, 0.20 );
+        if( res<0.005 || t>tmax ) break;
+    }
+    return clamp( res, 0.0, 1.0 );
+}
+
+float raycast(in vec3 ro, in vec3 rd, in float tmin, in float tmax  )
+{
+    vec4 kk;
+    float t = tmin;
+	for( int i=0; i<512; i++ )
+    {
+		vec3 p = ro + t*rd;
+        float h = map(p,kk,false);
+		if( abs(h)<(0.15*t/uResolution.x) ) break;
+		t += h*0.5;
+        if( t>tmax ) return -1.0;;
+	}
+    //if( t>tmax ) t=-1.0;
+
+    return t;
+}
+
+// void mainImage( out vec4 fragColor, in vec2 fragCoord )
+// gl_FragCoord.xy
+void main()
+{
+    float an = (uTime-10.0)*0.05;
+    
+    // camera	
+    vec3 ro = vec3( 4.5*sin(an), 0.0, 4.5*cos(an) );
+    vec3 ta = vec3( 0.0, 0.0, 0.0 );
+    // camera-to-world rotation
+    mat3 ca = makeBase( normalize(ta-ro) );
+
+    // render    
+    vec3 tot = vec3(0.0);
+    
+    #if AA>1
+    for( int m=ZERO; m<AA; m++ )
+    for( int n=ZERO; n<AA; n++ )
+    {
+        // pixel coordinates
+        vec2 o = vec2(float(m),float(n)) / float(AA) - 0.5;
+        vec2 p = (-uResolution.xy + 2.0*(gl_FragCoord.xy+o))/uResolution.y;
+        #else    
+        vec2 p = (-uResolution.xy + 2.0*gl_FragCoord.xy)/uResolution.y;
+        #endif
+        // ray direction
+        vec3 rd = ca * normalize( vec3(p.xy,2.2) );
+    
+        // background
+        vec3 col = vec3(0.1,0.14,0.18) + 0.1*rd.y;
+
+        // bounding volume
+        vec2 bound = sphIntersect( ro, rd, 2.1 );
+		if( bound.x>0.0 )
+        {
+        // raycast
+        float t = raycast(ro, rd, bound.x, bound.y );
+        if( t>0.0 )
+        {
+            // local geometry            
+            vec3 pos = ro + t*rd;
+        	vec3 nor = calcNormal(pos, 0.01);
+            vec3 upp = normalize(pos);
+            
+            // color and occlusion
+            vec4 mate; map(pos, mate, true);
+            
+            // lighting            
+            col = vec3(0.0);
+        
+            // key ligh
+            {
+                // dif
+                vec3 lig = normalize(vec3(1.0,0.0,0.7));
+                float dif = clamp(0.5+0.5*dot(nor,lig),0.0,1.0);
+                float sha = calcSoftshadow( pos+0.0001*nor, lig, 0.0001, 2.0, 6.0 );
+                col += mate.xyz*dif*vec3(1.8,0.6,0.5)*1.1*vec3(sha,sha*0.3+0.7*sha*sha,sha*sha);
+				// spec
+                vec3 hal = normalize(lig-rd);
+                float spe = clamp( dot(nor,hal), 0.0, 1.0 );
+                float fre = clamp( dot(-rd,lig), 0.0, 1.0 );
+                fre = 0.2 + 0.8*pow(fre,5.0);
+                spe *= spe;
+                spe *= spe;
+                spe *= spe;
+                col += 1.0*(0.25+0.75*mate.x)*spe*dif*sha*fre;
+            }
+
+            // back light
+           	{
+                vec3 lig = normalize(vec3(-1.0,0.0,0.0));
+                float dif = clamp(0.5+0.5*dot(nor,lig),0.0,1.0);
+                col += mate.rgb*dif*vec3(1.2,0.9,0.6)*0.2*mate.w;
+            }
+
+            // dome light
+            {
+                float dif = clamp(0.3+0.7*dot(nor,upp),0.0,1.0);
+                #if 0
+                dif *= 0.05 + 0.95*calcSoftshadow( pos+0.0001*nor, upp, 0.0001, 1.0, 1.0 );
+                col += mate.xyz*dif*5.0*vec3(0.1,0.1,0.3)*mate.w;
+                #else
+                col += mate.xyz*dif*3.0*vec3(0.1,0.1,0.3)*mate.w*(0.2+0.8*mate.w);
+                #endif
+            }
+            
+            // fake sss
+            {
+                float fre = clamp(1.0+dot(rd,nor),0.0,1.0);
+                col += 0.3*vec3(1.0,0.3,0.2)*mate.xyz*mate.xyz*fre*fre*mate.w;
+            }
+            
+            // grade/sss
+            {
+            	col = 2.0*pow( col, vec3(0.7,0.85,1.0) );
+            }
+            
+            // exposure control
+            col *= 0.7 + 0.3*smoothstep(0.0,25.0,abs(uTime-31.0));
+            
+            // display fake occlusion
+            //col = mate.www;
+        }
+        }
+    
+ 
+        // gamma
+        col = pow( col, vec3(0.4545) );
+    
+        tot += col;
+    #if AA>1
+    }
+    tot /= float(AA*AA);
+    #endif
+
+    // vignetting
+ 	vec2 q = gl_FragCoord.xy/uResolution.xy;
+    tot *= pow( 16.0*q.x*q.y*(1.0-q.x)*(1.0-q.y), 0.2 );
+    
+    fragColor = vec4( tot, 1.0 );
+}

psutil.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"io/ioutil"
+
+	"github.com/faiface/pixel"
+	"github.com/faiface/pixel/pixelgl"
+)
+
+// Pixel Shader utility functions
+
+// EasyBindUniforms does all the work for you, just pass in a
+// valid array adhering to format: String, Variable, ...
+//
+// example:
+//
+//   var uTimeVar float32
+//   var uMouseVar mgl32.Vec4
+//
+//   EasyBindUniforms(win.GetCanvas(),
+// 	     "u_time", &uTimeVar,
+// 	     "u_mouse", &uMouseVar,
+//   )
+//
+func EasyBindUniforms(c *pixelgl.Canvas, unifs ...interface{}) {
+	if len(unifs)%2 != 0 {
+		panic("needs to be divisable by 2")
+	}
+	for i := 0; i < len(unifs); i += 2 {
+
+		c.SetUniform(unifs[i+0].(string), unifs[i+1])
+	}
+}
+
+// CenterWindow will... center the window
+func CenterWindow(win *pixelgl.Window) {
+	x, y := pixelgl.PrimaryMonitor().Size()
+	width, height := win.Bounds().Size().XY()
+	win.SetPos(
+		pixel.V(
+			x/2-width/2,
+			y/2-height/2,
+		),
+	)
+}
+
+// LoadFileToString loads the contents of a file into a string
+func LoadFileToString(filename string) (string, error) {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}

seascape.glsl

@@ -0,0 +1,196 @@
+/*
+ * "Seascape" by Alexander Alekseev aka TDM - 2014
+ * License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
+ * Contact: tdmaav@gmail.com
+ */
+
+#version 330 core
+
+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;
+const float PI	 	= 3.141592;
+const float EPSILON	= 1e-3;
+#define EPSILON_NRM (0.1 / uResolution.x)
+
+// sea
+const int ITER_GEOMETRY = 3;
+const int ITER_FRAGMENT = 5;
+const float SEA_HEIGHT = 0.6;
+const float SEA_CHOPPY = 4.0;
+const float SEA_SPEED = 0.8;
+const float SEA_FREQ = 0.16;
+const vec3 SEA_BASE = vec3(0.1,0.19,0.22);
+const vec3 SEA_WATER_COLOR = vec3(0.8,0.9,0.6);
+#define SEA_TIME (1.0 + uTime * SEA_SPEED)
+const mat2 octave_m = mat2(1.6,1.2,-1.2,1.6);
+
+// math
+mat3 fromEuler(vec3 ang) {
+	vec2 a1 = vec2(sin(ang.x),cos(ang.x));
+    vec2 a2 = vec2(sin(ang.y),cos(ang.y));
+    vec2 a3 = vec2(sin(ang.z),cos(ang.z));
+    mat3 m;
+    m[0] = vec3(a1.y*a3.y+a1.x*a2.x*a3.x,a1.y*a2.x*a3.x+a3.y*a1.x,-a2.y*a3.x);
+	m[1] = vec3(-a2.y*a1.x,a1.y*a2.y,a2.x);
+	m[2] = vec3(a3.y*a1.x*a2.x+a1.y*a3.x,a1.x*a3.x-a1.y*a3.y*a2.x,a2.y*a3.y);
+	return m;
+}
+float hash( vec2 p ) {
+	float h = dot(p,vec2(127.1,311.7));
+    return fract(sin(h)*43758.5453123);
+}
+float noise( in vec2 p ) {
+    vec2 i = floor( p );
+    vec2 f = fract( p );
+	vec2 u = f*f*(3.0-2.0*f);
+    return -1.0+2.0*mix( mix( hash( i + vec2(0.0,0.0) ),
+                     hash( i + vec2(1.0,0.0) ), u.x),
+                mix( hash( i + vec2(0.0,1.0) ),
+                     hash( i + vec2(1.0,1.0) ), u.x), u.y);
+}
+
+// lighting
+float diffuse(vec3 n,vec3 l,float p) {
+    return pow(dot(n,l) * 0.4 + 0.6,p);
+}
+float specular(vec3 n,vec3 l,vec3 e,float s) {
+    float nrm = (s + 8.0) / (PI * 8.0);
+    return pow(max(dot(reflect(e,n),l),0.0),s) * nrm;
+}
+
+// sky
+vec3 getSkyColor(vec3 e) {
+    e.y = max(e.y,0.0);
+    return vec3(pow(1.0-e.y,2.0), 1.0-e.y, 0.6+(1.0-e.y)*0.4);
+}
+
+// sea
+float sea_octave(vec2 uv, float choppy) {
+    uv += noise(uv);
+    vec2 wv = 1.0-abs(sin(uv));
+    vec2 swv = abs(cos(uv));
+    wv = mix(wv,swv,wv);
+    return pow(1.0-pow(wv.x * wv.y,0.65),choppy);
+}
+
+float map(vec3 p) {
+    float freq = SEA_FREQ;
+    float amp = SEA_HEIGHT;
+    float choppy = SEA_CHOPPY;
+    vec2 uv = p.xz; uv.x *= 0.75;
+
+    float d, h = 0.0;
+    for(int i = 0; i < ITER_GEOMETRY; i++) {
+    	d = sea_octave((uv+SEA_TIME)*freq,choppy);
+    	d += sea_octave((uv-SEA_TIME)*freq,choppy);
+        h += d * amp;
+    	uv *= octave_m; freq *= 1.9; amp *= 0.22;
+        choppy = mix(choppy,1.0,0.2);
+    }
+    return p.y - h;
+}
+
+float map_detailed(vec3 p) {
+    float freq = SEA_FREQ;
+    float amp = SEA_HEIGHT;
+    float choppy = SEA_CHOPPY;
+    vec2 uv = p.xz; uv.x *= 0.75;
+
+    float d, h = 0.0;
+    for(int i = 0; i < ITER_FRAGMENT; i++) {
+    	d = sea_octave((uv+SEA_TIME)*freq,choppy);
+    	d += sea_octave((uv-SEA_TIME)*freq,choppy);
+        h += d * amp;
+    	uv *= octave_m; freq *= 1.9; amp *= 0.22;
+        choppy = mix(choppy,1.0,0.2);
+    }
+    return p.y - h;
+}
+
+vec3 getSeaColor(vec3 p, vec3 n, vec3 l, vec3 eye, vec3 dist) {
+    float fresnel = clamp(1.0 - dot(n,-eye), 0.0, 1.0);
+    fresnel = pow(fresnel,3.0) * 0.65;
+
+    vec3 reflected = getSkyColor(reflect(eye,n));
+    vec3 refracted = SEA_BASE + diffuse(n,l,80.0) * SEA_WATER_COLOR * 0.12;
+
+    vec3 color = mix(refracted,reflected,fresnel);
+
+    float atten = max(1.0 - dot(dist,dist) * 0.001, 0.0);
+    color += SEA_WATER_COLOR * (p.y - SEA_HEIGHT) * 0.18 * atten;
+
+    color += vec3(specular(n,l,eye,60.0));
+
+    return color;
+}
+
+// tracing
+vec3 getNormal(vec3 p, float eps) {
+    vec3 n;
+    n.y = map_detailed(p);
+    n.x = map_detailed(vec3(p.x+eps,p.y,p.z)) - n.y;
+    n.z = map_detailed(vec3(p.x,p.y,p.z+eps)) - n.y;
+    n.y = eps;
+    return normalize(n);
+}
+
+float heightMapTracing(vec3 ori, vec3 dir, out vec3 p) {
+    float tm = 0.0;
+    float tx = 1000.0;
+    float hx = map(ori + dir * tx);
+    if(hx > 0.0) return tx;
+    float hm = map(ori + dir * tm);
+    float tmid = 0.0;
+    for(int i = 0; i < NUM_STEPS; i++) {
+        tmid = mix(tm,tx, hm/(hm-hx));
+        p = ori + dir * tmid;
+    	float hmid = map(p);
+		if(hmid < 0.0) {
+        	tx = tmid;
+            hx = hmid;
+        } else {
+            tm = tmid;
+            hm = hmid;
+        }
+    }
+    return tmid;
+}
+
+// main
+void main()
+{
+	vec2 uv = gl_FragCoord.xy / uResolution.xy;
+    uv = uv * 2.0 - 1.0;
+    uv.x *= uResolution.x / uResolution.y;
+    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);
+    vec3 ori = vec3(0.0,3.5,time*5.0);
+    vec3 dir = normalize(vec3(uv.xy,-2.0)); dir.z += length(uv) * 0.15;
+    dir = normalize(dir) * fromEuler(ang);
+
+    // tracing
+    vec3 p;
+    heightMapTracing(ori,dir,p);
+    vec3 dist = p - ori;
+    vec3 n = getNormal(p, dot(dist,dist) * EPSILON_NRM);
+    vec3 light = normalize(vec3(0.0,1.0,0.8));
+
+    // color
+    vec3 color = mix(
+        getSkyColor(dir),
+        getSeaColor(p,n,light,dir,dist),
+    	pow(smoothstep(0.0,-0.05,dir.y),0.3));
+
+    // post
+	fragColor = vec4(pow(color,vec3(0.75)), 1.0);
+}

seascape.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"time"
+
+	"github.com/go-gl/mathgl/mgl32"
+
+	"github.com/faiface/pixel"
+	"github.com/faiface/pixel/pixelgl"
+	"golang.org/x/image/colornames"
+)
+
+import "log"
+import "github.com/gookit/config"
+
+func run() {
+	// Set up window configs
+	log.Println("width = ", config.Int("width"), "height = ", config.String("height"))
+	cfg := pixelgl.WindowConfig{ // Default: 1024 x 768
+		Title:  "Golang GLSL",
+		Bounds: pixel.R(0, 0,  config.Float("width"), config.Float("height")),
+		VSync:  true,
+	}
+
+	win, err := pixelgl.NewWindow(cfg)
+	if err != nil {
+		panic(err)
+	}
+
+	camVector := win.Bounds().Center()
+
+	bounds := win.Bounds()
+	bounds.Max = bounds.Max.ScaledXY(pixel.V(1.0, 1.0))
+
+	// I am putting all shader example initializing stuff here for
+	// easier reference to those learning to use this functionality
+
+	log.Println("Load GSGL file = ", config.String("filename"))
+	fragSource, err := LoadFileToString(config.String("filename"))
+
+	if err != nil {
+		panic(err)
+	}
+
+	var uMouse mgl32.Vec4
+	var uTime float32
+	log.Println("glDrift = ", config.String("glDrift"))
+	var glDrift float32 = float32(config.Float("glDrift"))
+
+	canvas := win.Canvas()
+	uResolution := mgl32.Vec2{float32(win.Bounds().W()), float32(win.Bounds().H())}
+
+	EasyBindUniforms(canvas,
+		"uResolution", &uResolution,
+		"uTime", &uTime,
+		"uMouse", &uMouse,
+		"uDrift", &glDrift,
+	)
+
+	canvas.SetFragmentShader(fragSource)
+
+	start := time.Now()
+
+	// Game Loop
+	for !win.Closed() {
+		uTime = float32(time.Since(start).Seconds())
+		mpos := win.MousePosition()
+		uMouse[0] = float32(mpos.X)
+		uMouse[1] = float32(mpos.Y)
+
+		win.Clear(colornames.Black)
+
+		// Drawing to the screen
+		canvas.Draw(win, pixel.IM.Moved(camVector))
+
+		win.Update()
+	}
+
+}
+
+func main() {
+	// This parses the command line arguments
+	parseConfig()
+
+	pixelgl.Run(run)
+}

seascape_original.glsl

@@ -0,0 +1,184 @@
+/*
+ * "Seascape" by Alexander Alekseev aka TDM - 2014
+ * License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
+ * Contact: tdmaav@gmail.com
+ */
+
+const int NUM_STEPS = 8;
+const float PI	 	= 3.141592;
+const float EPSILON	= 1e-3;
+#define EPSILON_NRM (0.1 / iResolution.x)
+
+// sea
+const int ITER_GEOMETRY = 3;
+const int ITER_FRAGMENT = 5;
+const float SEA_HEIGHT = 0.6;
+const float SEA_CHOPPY = 4.0;
+const float SEA_SPEED = 0.8;
+const float SEA_FREQ = 0.16;
+const vec3 SEA_BASE = vec3(0.1,0.19,0.22);
+const vec3 SEA_WATER_COLOR = vec3(0.8,0.9,0.6);
+#define SEA_TIME (1.0 + iTime * SEA_SPEED)
+const mat2 octave_m = mat2(1.6,1.2,-1.2,1.6);
+
+// math
+mat3 fromEuler(vec3 ang) {
+	vec2 a1 = vec2(sin(ang.x),cos(ang.x));
+    vec2 a2 = vec2(sin(ang.y),cos(ang.y));
+    vec2 a3 = vec2(sin(ang.z),cos(ang.z));
+    mat3 m;
+    m[0] = vec3(a1.y*a3.y+a1.x*a2.x*a3.x,a1.y*a2.x*a3.x+a3.y*a1.x,-a2.y*a3.x);
+	m[1] = vec3(-a2.y*a1.x,a1.y*a2.y,a2.x);
+	m[2] = vec3(a3.y*a1.x*a2.x+a1.y*a3.x,a1.x*a3.x-a1.y*a3.y*a2.x,a2.y*a3.y);
+	return m;
+}
+float hash( vec2 p ) {
+	float h = dot(p,vec2(127.1,311.7));
+    return fract(sin(h)*43758.5453123);
+}
+float noise( in vec2 p ) {
+    vec2 i = floor( p );
+    vec2 f = fract( p );
+	vec2 u = f*f*(3.0-2.0*f);
+    return -1.0+2.0*mix( mix( hash( i + vec2(0.0,0.0) ),
+                     hash( i + vec2(1.0,0.0) ), u.x),
+                mix( hash( i + vec2(0.0,1.0) ),
+                     hash( i + vec2(1.0,1.0) ), u.x), u.y);
+}
+
+// lighting
+float diffuse(vec3 n,vec3 l,float p) {
+    return pow(dot(n,l) * 0.4 + 0.6,p);
+}
+float specular(vec3 n,vec3 l,vec3 e,float s) {
+    float nrm = (s + 8.0) / (PI * 8.0);
+    return pow(max(dot(reflect(e,n),l),0.0),s) * nrm;
+}
+
+// sky
+vec3 getSkyColor(vec3 e) {
+    e.y = max(e.y,0.0);
+    return vec3(pow(1.0-e.y,2.0), 1.0-e.y, 0.6+(1.0-e.y)*0.4);
+}
+
+// sea
+float sea_octave(vec2 uv, float choppy) {
+    uv += noise(uv);
+    vec2 wv = 1.0-abs(sin(uv));
+    vec2 swv = abs(cos(uv));
+    wv = mix(wv,swv,wv);
+    return pow(1.0-pow(wv.x * wv.y,0.65),choppy);
+}
+
+float map(vec3 p) {
+    float freq = SEA_FREQ;
+    float amp = SEA_HEIGHT;
+    float choppy = SEA_CHOPPY;
+    vec2 uv = p.xz; uv.x *= 0.75;
+
+    float d, h = 0.0;
+    for(int i = 0; i < ITER_GEOMETRY; i++) {
+    	d = sea_octave((uv+SEA_TIME)*freq,choppy);
+    	d += sea_octave((uv-SEA_TIME)*freq,choppy);
+        h += d * amp;
+    	uv *= octave_m; freq *= 1.9; amp *= 0.22;
+        choppy = mix(choppy,1.0,0.2);
+    }
+    return p.y - h;
+}
+
+float map_detailed(vec3 p) {
+    float freq = SEA_FREQ;
+    float amp = SEA_HEIGHT;
+    float choppy = SEA_CHOPPY;
+    vec2 uv = p.xz; uv.x *= 0.75;
+
+    float d, h = 0.0;
+    for(int i = 0; i < ITER_FRAGMENT; i++) {
+    	d = sea_octave((uv+SEA_TIME)*freq,choppy);
+    	d += sea_octave((uv-SEA_TIME)*freq,choppy);
+        h += d * amp;
+    	uv *= octave_m; freq *= 1.9; amp *= 0.22;
+        choppy = mix(choppy,1.0,0.2);
+    }
+    return p.y - h;
+}
+
+vec3 getSeaColor(vec3 p, vec3 n, vec3 l, vec3 eye, vec3 dist) {
+    float fresnel = clamp(1.0 - dot(n,-eye), 0.0, 1.0);
+    fresnel = pow(fresnel,3.0) * 0.65;
+
+    vec3 reflected = getSkyColor(reflect(eye,n));
+    vec3 refracted = SEA_BASE + diffuse(n,l,80.0) * SEA_WATER_COLOR * 0.12;
+
+    vec3 color = mix(refracted,reflected,fresnel);
+
+    float atten = max(1.0 - dot(dist,dist) * 0.001, 0.0);
+    color += SEA_WATER_COLOR * (p.y - SEA_HEIGHT) * 0.18 * atten;
+
+    color += vec3(specular(n,l,eye,60.0));
+
+    return color;
+}
+
+// tracing
+vec3 getNormal(vec3 p, float eps) {
+    vec3 n;
+    n.y = map_detailed(p);
+    n.x = map_detailed(vec3(p.x+eps,p.y,p.z)) - n.y;
+    n.z = map_detailed(vec3(p.x,p.y,p.z+eps)) - n.y;
+    n.y = eps;
+    return normalize(n);
+}
+
+float heightMapTracing(vec3 ori, vec3 dir, out vec3 p) {
+    float tm = 0.0;
+    float tx = 1000.0;
+    float hx = map(ori + dir * tx);
+    if(hx > 0.0) return tx;
+    float hm = map(ori + dir * tm);
+    float tmid = 0.0;
+    for(int i = 0; i < NUM_STEPS; i++) {
+        tmid = mix(tm,tx, hm/(hm-hx));
+        p = ori + dir * tmid;
+    	float hmid = map(p);
+		if(hmid < 0.0) {
+        	tx = tmid;
+            hx = hmid;
+        } else {
+            tm = tmid;
+            hm = hmid;
+        }
+    }
+    return tmid;
+}
+
+// main
+void mainImage( out vec4 fragColor, in vec2 fragCoord ) {
+	vec2 uv = fragCoord.xy / iResolution.xy;
+    uv = uv * 2.0 - 1.0;
+    uv.x *= iResolution.x / iResolution.y;
+    float time = iTime * 0.3 + iMouse.x*0.01;
+
+    // ray
+    vec3 ang = vec3(sin(time*3.0)*0.1,sin(time)*0.2+0.3,time);
+    vec3 ori = vec3(0.0,3.5,time*5.0);
+    vec3 dir = normalize(vec3(uv.xy,-2.0)); dir.z += length(uv) * 0.15;
+    dir = normalize(dir) * fromEuler(ang);
+
+    // tracing
+    vec3 p;
+    heightMapTracing(ori,dir,p);
+    vec3 dist = p - ori;
+    vec3 n = getNormal(p, dot(dist,dist) * EPSILON_NRM);
+    vec3 light = normalize(vec3(0.0,1.0,0.8));
+
+    // color
+    vec3 color = mix(
+        getSkyColor(dir),
+        getSeaColor(p,n,light,dir,dist),
+    	pow(smoothstep(0.0,-0.05,dir.y),0.3));
+
+    // post
+	fragColor = vec4(pow(color,vec3(0.75)), 1.0);
+}