Basic template for utilizing a texture as an array and setting it up with data at specific columns/rows

array-setup.glsl

precision highp float;

// note - assuming OpenGL ES 2.0 - adjust as needed

// the number of items total you want to write out on each row
#define NUM 100

// the row of pixels to store, in this example positions
#define POSITION_ROW 2

// the row of pixels to store, in this example, colors.
#define COLOR_ROW 3


void main() {
  

  // figure out the position that we're sampling at. 
  int index = int(gl_FragCoord.x);
  int row = int(gl_FragCoord.y);
    
  // figure out if we're parsing the row storing all particle positions. 
  // positions are stored on row 10 
  bool isPos = row==POSITION_ROW;

  if(isPos){
      
     
   
    if(index < NUM){
      // write out your information here, will go to position row. 
      gl_FragColor = vec4(1.);
    }
    
  }else {
    // it's important to discard whatever you don't need.
    discard;
  }
}