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    PsyViz
  • About Me:
    Research officer by day, Creative coder by night.
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  • GLSL shader help
    With the release of the Processing 2.0 the integration of GLSL shaders through the PShader has sort of forced me into properly learning GLSL (not a bad thing - just a steep learning curve) but has thrown up a few questions which if anybody has a pointer would be much appreciated. Ok brief outline of what I'm trying to achieve, I took one of the the examples from the  http://thndl.com  GLSL tutorials and started hacking away to try and make an audio visualization rendered entirely in a fragment shader. 

    To do this I pass the left and right audio buffer data as float arrays into a GLSL shader and then use this to visualization of the waveforms. The first question is that when trying to index into the array containing the audio data I keep getting runtime errors - I think this is to do with dynamic access and that I need to create a dynamic uniform expression to index the array. I tried to get around this by creating a new array of floats but kept getting a redefinition error saying that I cannot convert a uniform float[] to a float[].

    I've posted the code below if anybody could point me in the right direction the last 5 hours of slowly removing my hair will have not been in vain  .

    Rich

    GLSL Fragment shader
    2. #ifdef GL_ES
    3. precision highp float;
    4. precision highp int;
    5. #endif

    7. #define PROCESSING_COLOR_SHADER

    9. uniform float time;
    10. uniform vec2 resolution;
    11. uniform vec2 mouse;
    12. uniform float audioLeft[1024];
    13. uniform float audioRight[1024];
    14. uniform float bufferSize;

    16. // Required by Processing's default vertex shader
    17. varying vec4 vertColor;

    19. // f will be used to store the color of the current fragment
    20. vec4 f = vec4(1.,1.,1.,1.);

    22. void main(void)
    23. {    
    24.   // c will contain the position information for the current fragment (from -1,-1 to 1,1)
    25.   vec2 c = vec2 (-1.0 + 2.0 * gl_FragCoord.x / resolution.x, 1.0 - 2.0 * gl_FragCoord.y / resolution.y) ;
    26.  
    27.           // mousepos will contain the current mouse position (from -1,-1 to 1,1)
    28. vec2 mousepos = -1.0 + 2.0 * mouse.xy / resolution.xy;
    29.                     
    30.   float t = time;
    31.         
    32.         // second problem line of code
    33.         float audioBufferLeft[1024] = audioLeft;
    34.  
    35.         // problem line of code 
    36.   int bufX = int(bufferSize * gl_FragCoord.x / resolution.x);

    38.   float yDiff = c.y - audioLeft[bufX];
    39. float yDiff1 = c.y - audioRight[bufX];
    40. float y = c.y + yDiff;
    41. float g = abs(0.3 / y);
    42. float h = abs(c.x);
    43. vec3 col = vec3(g * (1.0 - h), g * h, g * 1.5);
    44. f = vec4(col, 1.0);  
    45.     
    46.   // sin wave   
    47. //float y = c.y + 0.5 * sin(c.x * 3.14 - t);
    48.   //float g = abs(0.1 / y);
    49. //float h = abs(c.x);
    50. //vec3 col = vec3(g * (1.0 - h), g * h, g * 1.5);
    51. //f = vec4(col, 1.0);  

    53. gl_FragColor = f;
    54. }

    Processing Sketch
    1. import ddf.minim.*;

    3. Minim minim;
    4. AudioInput in;

    6. PShader myShader;

    8. void setup() {
    9.   size(1024, 1080, P2D);
    10.   noSmooth();

    12.   minim = new Minim(this);

    14.   in = minim.getLineIn();

    16.   myShader = loadShader("shader.glsl");
    17.   myShader.set("resolution", float(width), float(height));
    18.   myShader.set("bufferSize", 1024.0);
    19.   shader(myShader); 
    20. }

    22. void draw() {
    23.   background(0);
    24.   float[] left = new float[in.bufferSize()];
    25.   float[] right = new float[in.bufferSize()];
    26.   for (int i = 0; i < in.bufferSize(); i++)
    27.   {
    28.     left[i] = in.left.get(i);
    29.     right[i] = in.right.get(i);
    30.   }

    32.   myShader.set("audioLeft", left);
    33.   myShader.set("audioRight", right);
    34.   myShader.set("time", millis() / 1000.0);
    35.   myShader.set("mouse", float(mouseX), float(mouseY));
    36.   shader(myShader);

    38.   noStroke();
    39.   fill(0);
    40.   rect(0, 0, width, height);  

    42.   resetShader();
    43. }