[gtk+/wip/matthiasc/shadertoy: 91/91] Add an example shader

[Matthias Clasen <matthiasc src gnome org>]

commit 8e27005f976684f67b445dd3018dd40363dacc20
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Oct 2 21:30:47 2017 -0400

    Add an example shader
    
    fire.frag shows how one might do a transition
    between two children.

 demos/gtk-demo/fire.frag |   87 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 87 insertions(+), 0 deletions(-)
---
diff --git a/demos/gtk-demo/fire.frag b/demos/gtk-demo/fire.frag
new file mode 100644
index 0000000..1a974fd
--- /dev/null
+++ b/demos/gtk-demo/fire.frag
@@ -0,0 +1,87 @@
+#version 420 core
+
+layout(location = 0) in vec2 iPos;
+layout(location = 1) in vec2 iTexCoord1;
+layout(location = 2) in vec2 iTexCoord2;
+layout(location = 3) in float iTime;
+layout(location = 4) in vec2 iResolution;
+
+layout(set = 0, binding = 0) uniform sampler2D iTexture1;
+layout(set = 1, binding = 0) uniform sampler2D iTexture2;
+
+layout(location = 0) out vec4 color;
+
+// based on http://glslsandbox.com/e#35642.0
+
+vec3 TextureSource(vec2 uv)
+{
+       return texture(iTexture1, uv).rgb;;
+}
+
+vec3 TextureTarget(vec2 uv)
+{
+       return texture(iTexture2, uv).rgb;;
+}
+
+
+float Hash( vec2 p)
+{
+       vec3 p2 = vec3(p.xy,1.0);
+    return fract(sin(dot(p2,vec3(37.1,61.7, 12.4)))*3758.5453123);
+}
+
+float noise(in vec2 p)
+{
+    vec2 i = floor(p);
+       vec2 f = fract(p);
+       f *= f * (3.0-2.0*f);
+
+    return mix(mix(Hash(i + vec2(0.,0.)), Hash(i + vec2(1.,0.)),f.x),
+               mix(Hash(i + vec2(0.,1.)), Hash(i + vec2(1.,1.)),f.x),
+               f.y);
+}
+
+float fbm(vec2 p) 
+{
+       float v = 0.0;
+       v += noise(p*1.)*.5;
+       v += noise(p*2.)*.25;
+       v += noise(p*4.)*.125;
+       return v;
+}
+
+void mainImage( out vec4 fragColor, in vec2 fragCoord )
+{
+       vec2 uv = iTexCoord1;
+       vec3 src = TextureSource(uv);
+       vec3 tgt = TextureTarget(uv);
+       vec3 col = src;
+
+       uv.x -= 1.5;
+
+        if (iTime <= 0) {
+          fragColor.rgb = src.rgb;
+          return;
+        }
+        else if (iTime > 5) {
+          fragColor.rgb = tgt.rgb;
+          return;
+        }
+
+       float ctime = iTime*.5;
+       // burn
+       float d = uv.x+uv.y*0.5 + 0.5*fbm(uv*15.1) + ctime*1.3;
+       if (d >0.35) col = clamp(col-(d-0.35)*10.,0.0,1.0);
+       if (d >0.47) {
+               if (d < 0.5 ) col += 
(d-0.4)*33.0*0.5*(0.0+noise(100.*uv+vec2(-ctime*2.,0.)))*vec3(1.5,0.5,0.0);
+               else col += tgt; }
+
+       fragColor.rgb = col;
+}
+
+
+
+void main()
+{
+  mainImage (color, iPos);
+}