Hey there
I'm trying to import a shader from ShaderToy in Pure data and I don't know what to do about "iChannel0". What can I do in my shader.frag ?
The use of "iChannel" (0, 1 and more) in ShaderToy is clear but I don't know how transform it for Pure Data. It appear everytime a shader use a noise animation and it's happend often.
An example of a shader with this function line 19 https://www.shadertoy.com/view/lslXRS

Any advice is appreciated. Thank you.

@Martin_LM Are you trying to use [glsl_fragment] in Pd......... from the Gem library.
If not, then you probably should.
Also.... https://forum.pdpatchrepo.info/topic/3835/blur-gemframebuffer
David.

@whale-av said:

https://forum.pdpatchrepo.info/topic/3835/blur-gemframebuffer

Yes I'm working with [glsl_vertex], [glsl_fragment] and [glsl_program].
In Gem exemples like "simple_texture.pd", they use [pix_image] in the pd patch (in the gemhead chaine, after [glsl_program]) to load a image.jpg.
They create a "uniform sampler2D MyTex;" in the .frag.
I don't understand the link between MyTex and [pix_image].

I'm trying to do the same in the shader (from shadertoy in my first post) by replacing "float noise( in vec2 x ){return texture(iChannel0, x*.01).x;}" by
"float noise( in vec2 x ){return texture2D(MyTex, x*.01).x;}",
after I had create my uniform sampler2D MyTex; of course.
I'm loading the same texture it's use in shadertoy but It does nothing.
There is not so many tutorial about glsl in Pure Data...

@Martin_LM Ok. I have never tried it, but someone else will get involved with your thread I am sure.

If you don't have it, then you should download this...... https://puredata.info/downloads/extended-view-toolkit.
It has, in its "ev-glsl" folder a help file and other files that use glsl. No tutorial, but you might well find some clues.
It could be as simple as the message ordering in Pd.
David.
PS.......****...... You will also find some dot.frag files that are used in their associated objects, and are recognisable when looking inside as the program to be run........ so you can see how they relate and communicate.

I'll try to find something in the toolkit, maybe I'll find the solution to do that.
Thx !

for easy to use "shadertoy glsl" to "gem glsl" you can use theses examples here :
https://github.com/danomatika/BangYourHead/tree/master/7.Graphics/10.Shaders/2.ShaderToy

basically you have to copy/paste this glsl header code to be compliant with gem :

/////////////////////////start Pd Header
// 2015 Sofy Yuditskaya
// put all the shadertoy constants here for ease of use

uniform vec3      iResolution;           // viewport resolution (in pixels)
uniform float     iGlobalTime;           // shader playback time (in seconds)
uniform float     iTimeDelta;            // render time (in seconds)
uniform int       iFrame;                // shader playback frame
uniform float     iChannelTime[4];       // channel playback time (in seconds)
uniform vec3      iChannelResolution[4]; // channel resolution (in pixels)
uniform vec4      iMouse;                // mouse pixel coords. xy: current (if MLB down), zw: click

// changed samplerXX to sampler2D so it would be recognized, you can also change it to samplerCube as needed

uniform sampler2D iChannel0;          // input channel. XX = 2D/Cube
uniform sampler2D iChannel1;          // input channel. XX = 2D/Cube
uniform sampler2D iChannel2;          // input channel. XX = 2D/Cube
uniform sampler2D iChannel3;          // input channel. XX = 2D/Cube

uniform vec4      iDate;                 // (year, month, day, time in seconds)
uniform float     iSampleRate;           // sound sample rate (i.e., 44100)

void mainImage(out vec4 fragColor, in vec2 fragCoord);

// changelog for Pd:
//running mainImage() from main()
// declared Shadertoy's usual variables above
// declared iChannel0...3 variables individually

void main(  )
{
    mainImage(gl_FragColor, gl_FragCoord.xy);
}
//paste ShaderToy code below
/////////////////////////end Pd Header

The educational resources for combining Pd/GEM with GLSL are indeed quite limited.

I also found the BangYourHead repository which gives some nice examples for standalone GLSL use, but if you want to know how to combine pix-objects with glsl you are a bit lost.

For my current research (trying to combine [pix_freenect] with glsl) I found this patch quite useful: https://github.com/kronihias/pd-kinect-examples/blob/master/02-background-subtraction/02-01-background-subtraction-opengl-shader.pd

(although I don't fully understand where the DepthMap uniform variable is coming from)

@dreamer with Ofelia it is quite easy to use textures (pix is basically for using textures with Gem, if I understand it right) with GLSL, here is an example: ofelia_glsl_blend_2_images.zip