Velocity Color Tracers

A Fun Tutorial Blending Physics and Color:

In this project we learn how to make a movable ball leave behind a trail of tracer balls, each a color representing the movable ball's speed at that point in space / time. 

Video Tutorial on How to Build "Velocity Color Tracers" 

What you'll learn:

• Physics:
  • Working with Speed via script: Linear velocity magnitude 
  • Components of velocity: velocity in the Y direction 
• Emitters: 
  • "Moving": emit my sample object when the emitter moves.
  • "Clone as 'copy' ": clone the item I emit as a full copy with its own set of properties, not sharing properties with the source of the clone. 
  • onEmit() event / function:  The onEmit() function happens right before the emitter emits the objectd and gives you a chance to change properties on the emitted object.  
• Color:  
  • Hue Saturation Brightness.  
  • How to use hsb() to set color in script
• Scripting: 
  • Working with linear velocity.
  • Working with hue saturation and brightness for changing color in script.
  • Print statement.
• Movable Ball Actor: 
  • Setting properties to give the ball more power and change maximum speed. 
• Basic Construction:
  • Basic object hierarchy work

Script Used in this Tutorial:

function NodeEmitter:onEmit(obj)
	vel = self:getParentNode():getRigidBody():getLinearVelocity():length()
	--print(tostring(vel)) 

	obj.color = hsb(  ( 180 + (vel*10)) ,1,1)
end