[GLGraphics] Sending an array of variables to a GLSL shader?

amnon.owed

[GLGraphics] Sending an array of variables to a GLSL shader?

in Contributed Library Questions • 1 year ago

I've been using GLGraphics to work with -for now mainly fragment- shaders. All computation is handled within the shader which is working really well. To tweak settings in real-time, I'm sending some (uniform) variables from Processing to the shader. Again, working fine.

Now I'd like to send an array of variables* to the shader. Is this possible in GLGraphics? And if so, how?

* meaning: more variables than 4 floats into a vec4, rather something like vec2[20] or vec3[8]

Replies(6)

andres

Re: [GLGraphics] Sending an array of variables to a GLSL shader?

1 year ago

The GLSLShader class doesn't expose the glUniformNfv (glUniform1fv, glUniform2fv, etc) you would need to pass an array of values to the shader. As a workaround, you could just call them after grabbing a reference to the GL object:

GLGraphics renderer = (GLGraphics)g;
GL gl = renderer.gl;
...
shader.start();
float[] values = {0.4, -0.1, 5.2, 1.0};
int loc = shader.getUniformLocation("parameters")
gl.glUniform1fv(loc, values.length, values, 0);
...

amnon.owed

Re: [GLGraphics] Sending an array of variables to a GLSL shader?

1 year ago

Thanks andres.

I forgot to mention my program runs the fragment shader through the GLTextureFilter class. It is very convenient as it returns the result directly into the GLTexture. I will try out your suggestion with the GLSLShader class. However, is something like this also possible when using the GLTextureFilter class?

amnon.owed

Re: [GLGraphics] Sending an array of variables to a GLSL shader?

1 year ago

All right, I have tested your suggestion using a quad and a GLSLShader. It works!

Still would appreciate to hear a similar route for the GLTextureFilter class if available...

andres

Re: [GLGraphics] Sending an array of variables to a GLSL shader?

1 year ago

Actually, you can set a filter parameter of type "array" which you can use to store arrays of floats of arbitrary length. For instance, to define a float array of 7 elements, you should add to the filter's xml file a line similar to this:

<parameter type="array" name="params" label="Effect parameters">0 0 0 0 0 0 0</parameter>

The 7 zeroes are the initial default values that the filter puts in the array.

amnon.owed

Re: [GLGraphics] Sending an array of variables to a GLSL shader?

1 year ago

Great! Tested and working as well.

With these two solutions I have different routes to realise what I want.

What I like a lot about the manual glUniformNfv solution is that it's very easy to pour a float array into another data type array like vec2, vec3 or vec4 which might make more sense within the context of the shader. Is such a float to vecN array transfer also possible with GLTextureFilter parameters?

andres

Re: [GLGraphics] Sending an array of variables to a GLSL shader?

1 year ago

No, the array parameter in GLTextureFilter only supports float elements.

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