Making an AfterImage Effect

To get the after image effect to work, simply drop the block of code below into a script and make sure to execute it! As is, it works nicely for animated sprites and static sprites. (I tested it for those on TGB 172.) Feel free to post questions, suggestions, or contributions! ;)

Here's the meat of the effect:

//**simple after image motion blur effect for animated sprites**
//frequency - how often to make after image clones (copies of object that fade out)
//duration - how long the effect will last
//owner visible - if true, the owner stays visible during the entire effect
//                if false, the owner disappears during the effect, and reappears
//                at the end.
//still frames - if true, then the copies are forced to render the same exact frame
//               as the owner had when the particular copy was made. Bit of a hacked
//               solution. Changes the frame back to previous one on an onFrameChange
//               callback.
//increment, speed, goal - all of these parameters are used soly for the fadeOut
//                         function. Increment is the number by which to reduce
//                         the alpha each speed interval which is in milliseconds.
//                         Goal tells the function when to stop fading.
function t2dAnimatedSprite::doSimpleAfterImageEffect(%this, %frequency, %duration, %ownerVisible, %stillFrames, %increment, %speed, %goal)
{
   for(%i = 0; %i < %duration; %i += %frequency)
   {
      %this.schedule(%i, "createAfterImageClone", %stillFrames, %increment, %speed, %goal);
   }
   
   if(!%ownerVisible)
   {
      %this.visible = false;
      %this.schedule(%duration, "setVisible", true);
   }
}

//used by the after image effects to produce copy images.
function t2dAnimatedSprite::createAfterImageClone(%this, %stillFrames, %increment, %speed, %goal)
{
   %clone = new t2dAnimatedSprite()
   {
      scenegraph = %this.getSceneGraph();
      class = "afterImageObject";
      size = %this.getSize();
      position = %this.getPosition();
      layer = (%this.getLayer() + 1);
      flipX = %this.FlipX;
      rotation = %this.getRotation();
      animationName = %this.getAnimation();
   };
   %clone.setAnimationFrame(%this.getAnimationFrame());
   %clone.fadeOut(%increment, %speed, %goal);
   //the next line assumes that your goal is 0. It just automatically computes a safe waiting
   //time for the deletion of the clone. Use the commented line after it to manually control
   //the deletion. Make sure to comment the automated line.
   %clone.schedule(((((1 - %increment) * %speed)/43) * 1500), "safeDelete");
   //%clone.schedule([int in milliseconds] "safeDelete");
   
   if(%stillFrames)
      %clone.setFrameChangeCallback(true);
}

//hacked solution to freeze an animation
function afterImageObject::onFrameChange(%this, %frameIndex)
{
   %this.setAnimationFrame(%frameIndex - 1);  
}

function t2dStaticSprite::doSimpleAfterImageEffect(%this, %frequency, %duration, %ownerVisible, %increment, %speed, %goal)
{
   for(%i = 0; %i < %duration; %i += %frequency)
   {
      %this.schedule(%i, "createAfterImageClone", %increment, %speed, %goal);
   }
   
   if(!%ownerVisible)
   {
      %this.visible = false;
      %this.schedule(%duration, "setVisible", true);
   }
}

function t2dStaticSprite::createAfterImageClone(%this, %increment, %speed, %goal)
{
   %clone = new t2dStaticSprite()
   {
      scenegraph = %this.getSceneGraph();
      class = "afterImageObject";
      size = %this.getSize();
      position = %this.getPosition();
      layer = (%this.getLayer() + 1);
      flipX = %this.FlipX;
      rotation = %this.getRotation();
      imageMap = %this.getImageMap();
   };
   %clone.fadeOut(%increment, %speed, %goal);
   //the next line assumes that your goal is 0. It just automatically computes a safe waiting
   //time for the deletion of the clone. Use the commented line after it to manually control
   //the deletion. Make sure to comment the automated line.
   %clone.schedule(((((1 - %increment) * %speed)/43) * 1500), "safeDelete");
   //%clone.schedule([int in milliseconds] "safeDelete");
}

Of course, a fading function is also quite needed:

//This function makes the object gradually disappear.
function t2dSceneObject::fadeOut(%this, %increment, %speed, %goal)
{
    if(isEventPending(%this.fadeInSchedule))
        cancel(%this.fadeInSchedule);
    
    %curAlpha = %this.getBlendAlpha();
    
    %this.setBlendAlpha(%curAlpha - %increment);
    
    if(%this.getBlendAlpha() >= %goal)
        %this.fadeOutSchedule = %this.schedule(%speed, "fadeOut", %increment, %speed, %goal);
    
    else
    {
        %this.setBlendAlpha(%goal);
        cancel(%this.fadeOutSchedule);
    }
}

Here is a good default line to call the after image effect:

someObject.doSimpleAfterImageEffect(100, 1500, false, true, 0.14, 50, 0);

This basic method could be easily adapted to incorporate virtually any type of TGB object.

Screenshot:

Contacting Me:

I am Kevin James and I approve this message. You can contact me here: syreal [at] syrealgames [dot] com