I start this addon while I was working on Efecto Mariposa. Is the result of adapting different well know algorithms to GLSL Shaders for openFrameworks.

An important feature of ofxFX is it ability for fast-prototyping mixing different classes using the << operator.

ofxFX was originally develop for GLSL 120 but now is been edited to support openGL ES and openGL 2.0 thanks to the new programable render of openFrameworks. Oliver is giving me a hand with that. Anybody else that want to collaborate is wellcome.

It´s the parent class of all the other effect. If you want to make a new filter you may want to start looking at the ofxFXObject.h .

The structure it´s easy.

1. Constructor: here it´s necessary to set three vital variables:

   • int passes: the number of passes or itineration of the main ping pong betweens FBO´s
   • int internalFormat: if it use GL_RGB, GL_RGBA, GL_RGB16f, GL_RGBA16f, GL_RGB32f, GL_RGBA32f, etc...
   • string fragShader: it´s the code of the shader. Note that some changes have to be made in order to fill everything on a string

2. allocate(width,height,GL_RGBA): This usually it´s no need to be re-define. It´s basically allocate the FBO´s and loads the shader by using injectShader();

3. setCode(string fragContent): here is where the shaders are loaded. See the example below.

4. begin(int texN) and end(int texN): remember nTextures variable? you can passthrough information to it by using this end() and begin() and giving the argument the number of texture you want to open. This texture can be access from the shader by the uniform sample2DRect tex0 or tex1 or tex2 and so on.

   4.1. << and setTexture(texture-like, num=0) if you have an FBO, a texture, an ofxFXObject, or something similar, you can use this function to write it to tex0, tex1, etc (as indicated by the num argument). << always writes to tex0.

   4.2. If you're making a multi-pass shader, you can access to the previously rendered frame with uniform sample2DRect backbuffer in your shader. This will also contain the information from tex0 on the first pass.

5. update(): This is the core of the class, where the magic happens. If you check for the ofxFXObject::update() you will see how the tex's, the backbuffer and other default uniforms variables (time, mouse, resolution) are loaded. NOTE: If you are using the << operator you don't need to update. It's done automatically for you

6. draw(x,y,w,h): After all you definitely want to look at it.

ofxFXObject have some handy operators that let you combine them really easily. At the Mix´s Example you will find how to do it. Basicaly it´s somethin like this

ofxFXObject objA;
ofxGrayScott objB;
ofxBlur     blur;

objA.allocate(width, height);
objB.allocate(width, height);
blur.allocate(width, height);

...

blur << (objB << objA);

...

blur.draw();