Run GLSL in Lua

Usage

pw.glsl(GLSLcode[, useBuffer])

• GLSLcode: string, the source fragment code. If your input code can be run in GLSL Render Mode, it can be directly used in here. (Codes from shadertoy.com is not supported here.)
• useBuffer : bool, optional, by default, this is set to false. If this is true, PixelsWorld will generate a temp memory to store your render result. When the GLSL render done, these data in temp memory will override the output layer's pixels data.
  
  Case you should set useBuffer to true:
• You want to re-read pixels from out layer. (Namely, there is getColor(OUTPUT_LAYER_INDEX,uv) in your glsl code)
• You want to make render slow.

  If you render glsl only one time each frame, you can totally ignore this option.

Here are some code to describe the useBuffer :

Tips:
Use [==[ and ]==] to enclose the multi-line code.

pw.glsl(
    [==[
        void main(){
            outColor = vec4(uv,0,1);
        }
    ]==]
);

pw.glsl(
    [==[
        void main(){
            vec3 outlayerColor = getColor(OUTPUT_LAYER_INDEX,uv).rgb;
            outColor = vec4(vec3(1)-outlayerColor,1);
        }
    ]==],true
);

pw.glsl(
    [==[
        void main(){
            outColor = vec4(uv,0,1);
        }
    ]==]
);

pw.glsl(
    [==[
        void main(){
            vec3 outlayerColor = getColor(OUTPUT_LAYER_INDEX,uv).rgb;
            outColor = vec4(vec3(1)-outlayerColor,1);
        }
    ]==],false
);

Speed it up

The efficiency of the approach mentioned above is pretty LOW.

That is because once we run the code, PixelsWorld returns the result to Ae. Then the next shader function need to read it back to perform the second shading. That's inefficiency

Unless you want to read pixels to do some CPU calculation between this two shader, the most case is we want the PixelsWorld returns the result in the end, not in every shading.

Then you need to write it this way:

pw.beginShaders()
pw.glsl(First glsl code)
pw.glsl(Second glsl code)
...
pw.glsl(Nth glsl code)
pw.endShaders()

We quote shaders by pw.beginShaders() and pw.endShaders(). Then the PixelsWorld only report result to Ae when pw.endShaders is called.

This is very efficient! The algorithm of it is to create a "Game Loop" between beginShaders and endShaders.

Tip: You can only write pw.beginShaders, PixelsWorld can add the pw.endShaders at the end automatically.

pw.shadertoy and pw.full_glsl are also support.

pw.beginShaders()
pw.glsl(glsl code)
pw.glsl(glsl code)
pw.shadertoy(shadertoy code)
pw.glsl(glsl code)
pw.full_glsl(full_glsl code)
pw.endShaders()

Note: All shaders between beginShaders and endShaders can read the result of last shaders. Use getColor(-2,uv) or getColor(OUTPUT_LAYER_INDEX,uv) or texture(outLayer,uv) or (in shadertoy mode) texture(_PixelsWorld_outLayer,_PixelsWorld_uv)

Flow chart