Tails, You Win – 3D Trails In Papervision
I'm not really sure where the inspiration came from, but I decided to take a stab at doing Motion Trails with Pv3D. Instead, I ended up with something more like a tail - but left the class name MotionTrail... Anyways - there isn't a whole lot to say on the technique I used here - but I will give a general overview just to save you looking at code. See the Demo.
The tail is defined by Number3D objects which "chase" each other, with the head node being pinned to the target you are chasing. Each Number3D, which I've extended into a Trail3D class (its internal - just look in the MotionTrail.as file) - springs after the node ahead of it. You can control this "springyness" by adjusting the minEase property of the MotionTrail. The minEase refers to the ease amount of the very last node on the tail - which increases each node up to the head, which has an ease of 1. So, the lower you set minEase, the slinkier the tail will end up looking. You can control how many nodes are in the tail by adjusting the "iterations" parameter of the MotionTail class. You need at least 2.
The tail is actually a triangle strip, which progressively gets smaller the closer to the end it gets. This 1) lets you use any material you want, and 2)easily adjust the look and feel of the tail all you want. Feel free to override it to affect the width with speed, distance, or any other cool variables you want. It looked good just tapering so I left it that way. The triangle strips vertices are adjusted to their corresponding TrailNode, so they always face the camera. This keeps the tail visible from any direction. Again, you could change this if you wanted it to be a more obvious flat tail. My initial idea was to use the delta properties of the adjacent nodes to determine the nodes up vector (find the cross product between the dx/dy/dz values of the nodes on either side of the current node) - but again - I liked how this looks so I left it.
The demo itself just makes use of some bezier curves to keep things moving smoothly. You will notice the nodes are flocking - but really it is just setting the control point and end point of each node within a certain range - which changes positions when the first object arrives. You can press "F" to toggle it so that each node has its own unique path.
Anyways - here is the code,
and another look at the demo
enjoy.
Source: http://blog.zupko.info
