• Adobe After Effects Expressions

  Expanding mask script in a 3D comp (space transform issues)

  Posted by Theo Burtis on April 8, 2021 at 4:40 pm

  Hi there,

  I’m working on motion graphics for a documentary that’s going need to a lot of expanding masks.

  I thought I’d try and save a little time by writing a script that would create mask paths based on the position value of a null.

  Surely someone has written exactly this script before, and I’d see the answer right in front of me if I understood the space transform functions a little better.

  If y’all don’t mind taking a look, I’d be much obliged,

  Thank you very much!

  -Theo B.

  //this mask expands right to left

  //this section translates the start position from the controller’s layer space to the mask’s layer space.

  var Start_Time = thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Start_Time”)(“Slider”);
  var controllerSpace_Position = thisComp.layer(“Write-on_Controller-RectangularMask”).transform.position;
  var compSpace_Position = thisComp.layer(“Write-on_Controller-RectangularMask”).toComp([controllerSpace_Position[0],controllerSpace_Position[1],controllerSpace_Position[2]]);

  //this section defines start and end positions for the expanding mask based on controller’s position.

  var layerSpace_StartPosition = thisLayer.fromComp(compSpace_Position, Start_Time);
  var layerSpace_EndPosition = thisLayer.fromComp(compSpace_Position);

  //this section seperates the start and end variables into X and Y values.

  var StartPoint_Xpos = layerSpace_StartPosition[0];
  var StartPoint_Ypos = layerSpace_StartPosition[1];
  var EndPoint_Xpos = layerSpace_EndPosition[0];
  var EndPoint_Ypos = layerSpace_EndPosition[1];

  //this section creates mask verticies using the above X and Y values.

  var maskDiameter = (thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Mask_Width”)(“Slider”))/2;

  var top_right = [StartPoint_Xpos,(StartPoint_Ypos – maskDiameter)];
  var bottom_right = [StartPoint_Xpos,(StartPoint_Ypos + maskDiameter)];
  var bottom_left = [EndPoint_Xpos,(EndPoint_Ypos + maskDiameter)];
  var top_left = [EndPoint_Xpos,(EndPoint_Ypos – maskDiameter)];
  var maskVerticies = [top_left,top_right,bottom_right, bottom_left];
  createPath(maskVerticies, inTangents = [], outTangents(), isClosed = true);

  Theo Burtis replied 5 years, 5 months ago 1 Member · 2 Replies
• 2 Replies

• 

  Theo Burtis

  April 9, 2021 at 5:00 pm

  Update:

  This version is a lot closer and cleaner, but the start point is still in the wrong place:

  //This mask expands left to right from a point designated by a slider effect in a separate null object layer.

  var StartPosition_Slider = thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Start_Point”)(“3D Point”)
  var StartPosition_CompSpace = thisLayer.toComp(StartPosition_Slider);
  var StartPosition = thisLayer.fromComp(StartPosition_CompSpace);
  //space transform from slider position in null object space to to mask layer space.

  var Start_Time = thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Start_Time”)(“Slider”)
  var End_Time = Start_Time + (thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Duration”)(“Slider”));
  var maskWidth = thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Mask_Width”)(“Slider”);
  var maskLength = thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Mask_Length”)(“Slider”);
  var Expansion = ease(time, Start_Time, End_Time , 0, maskLength);
  //defines mask expansion parameters.

  var topRight = [StartPosition[0],(StartPosition[1] – (maskWidth/2))]
  var bottomRight = [StartPosition[0],(StartPosition[1] + (maskWidth/2))]
  var bottomLeft = [StartPosition[0] – Expansion ,(StartPosition[1] + (maskWidth/2))]
  var topLeft = [StartPosition[0] – Expansion ,(StartPosition[1] – (maskWidth/2))]
  var maskVertices = [topRight,bottomRight,bottomLeft,topLeft]
  //defines mask vertices based on expansion parameters.

  createPath(maskVertices, [], [], isCLosed = true);

  Despite all the tutorials I’ve watched I still don’t quite understand what combination of toComp and fromComp I need to make this work. If you’ve got any ideas I’m all ears!

  Thx,

  -Theo B.
• 

  Theo Burtis

  April 11, 2021 at 2:45 am

  Solved:

  //This mask expands left to right from a point designated by a slider effect in a seperate null object layer.

  var StartPosition_Slider = thisComp.layer(“Write-on_Controller-RectangularMask”).transform.position
  var StartPosition_CompSpace = thisComp.layer(“Write-on_Controller-RectangularMask”).toComp(StartPosition_Slider);
  var StartPosition = thisLayer.fromComp(StartPosition_CompSpace);
  //space transform from slider position in null object space to to mask layer space.

  var Start_Time = thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Start_Time”)(“Slider”)
  var End_Time = Start_Time + (thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Duration”)(“Slider”));
  var maskWidth = thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Mask_Width”)(“Slider”);
  var maskLength = thisComp.layer(“Write-on_Controller-RectangularMask”).effect(“Mask_Length”)(“Slider”);
  var Expansion = ease(time, Start_Time, End_Time , 0, maskLength);
  //defines mask expansion parameters.

  var topRight = [StartPosition[0],(StartPosition[1] – (maskWidth/2))]
  var bottomRight = [StartPosition[0],(StartPosition[1] + (maskWidth/2))]
  var bottomLeft = [StartPosition[0] – Expansion ,(StartPosition[1] + (maskWidth/2))]
  var topLeft = [StartPosition[0] – Expansion ,(StartPosition[1] – (maskWidth/2))]
  var maskVertices = [topRight,bottomRight,bottomLeft,topLeft]
  //defines mask vertices based on expansion parameters.

  createPath(maskVertices, [], [], isClosed = true);

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