• Adobe After Effects Expressions

  Normalize Vector Issue

  Posted by Jamie Bradshaw on September 12, 2010 at 9:29 am

  Hi all.

  I have the following expression code on a Text Layer’s Source Text (for debugging purposes).

  It’s working fine except that I’m only getting different random values for each array (pArray1) when I normalize the vector (normalise = true)

  In other words, if I set the variable normalise to false then each of the pArray1 amounts come out the same.

  Any idea why?

  Thanks,
  Jamie

  
seedRandom(index, true);

  parentType1 = [0, 0, 0];
  parentAmount1 = 4;
  minMax1 = [-1, 1];
  normalise1 = true;

  pArray1 = generateParents(parentType1, parentAmount1, minMax1, normalise1);

  str1 = "";
  for (n1 = 0; n1 < parentAmount1; n1++) {
  str1 += "Parent " + n1 + "\r";
  for (n2 = 0; n2 < parentType1.length; n2++) {
  str1 +=
  "\t" + "[" + n2 + "]: " + pArray1[n1][n2] + "\t" + "\r";

  }
  str1 += "\t" + "length: " + length(pArray1[n1]) + "\r" +
  "\r";
  }

  function generateParents(pType_1, pAmount_1, minMax_1, norm_1) {
  var pArray_1 = new Array();
  var pType_2 = new Array();
  for (n_2 = 0; n_2 < pAmount_1; n_2++) {
  for (n_1 = 0; n_1 < pType_1.length; n_1++) {
  pType_2[n_1] = random(minMax_1[0], minMax_1[1]);
  }
  if (norm_1) {
  pType_3 = normalize(pType_2);
  } else {
  pType_3 = pType_2;
  }
  pArray_1[n_2] = pType_3;
  }
  return(pArray_1);
  }

  JimJam•Graphics
  https://www.jimjamgraphics.com/

  Jamie Bradshaw replied 15 years, 8 months ago 1 Member · 1 Reply
• 1 Reply

• 

  Jamie Bradshaw

  September 13, 2010 at 9:27 am

  Aha! Caught it!

  For anyone who might be vaguely interested it was because I needed to declare the var pArray_2 = new Array(); inside the first for loop. I’m guessing so that it could clear the previous info stored in the array which it wasn’t doing if I didn’t normalize the vector.

  Here is the working code with added comments to maybe make it clearer.

  
seedRandom(index , true);

  // The variables
  parentType1 = [0, 0, 0]; //define the parent type, in this case a 3d vector
  parentAmount1 = 4; //define how many original parents
  minMax1 = [-1, 1]; //define the min and max range of random values
  normalise1 = true; //normalise the vector or not
  generations1 = 20; //how many generations or iterations to calculate

  pArray1 = generateParents(parentType1, parentAmount1, minMax1, normalise1);

  // generate the debug text so I can assess what's happening
  str1 = "";
  for (n1 = 0; n1 < parentAmount1; n1++) {
  str1 += "Parent " + n1 + "\r";
  for (n2 = 0; n2 < parentType1.length; n2++) {
  str1 +=
  "\t" + "[" + n2 + "]: " + pArray1[n1][n2] + "\t" + "\r";
  }
  str1 += "\t" + "length: " + length(pArray1[n1]) + "\r" +
  "\r";
  }

  // ***FUNCTIONS***

  // this function returns an array of original parents
  function generateParents(pType_1, pAmount_1, minMax_1, norm_1) {
  var pArray_1 = new Array();
  var pType_3 = new Array();
  for (n_2 = 0; n_2 < pAmount_1; n_2++) {
  var pType_2 = new Array();
  for (n_1 = 0; n_1 < pType_1.length; n_1++) {
  pType_2[n_1] = random(minMax_1[0], minMax_1[1]);
  }
  if (norm_1 == false) {
  pType_3 = pType_2;
  } else {
  pType_3 = normalize(pType_2);
  }
  pArray_1[n_2] = pType_3;
  }
  return(pArray_1);
  }

  JimJam•Graphics
  https://www.jimjamgraphics.com/

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