MAXON Computer Cinema 4D Tutorials: Modeling Using Tangential Spline Animations in three easy steps

Tips & Techniques - Modeling

Modeling:
Modeling Using Tangential Spline Animations in three easy steps
Download:
PDF / Project Works with:
Cinema 4D XL Requires:
Version 5.x

Warning:
A word of warning before we begin though - there are some limitations. I have found that every time a spline in Cinema nears a parallel with the global Y axis that it experiences a 180 degree rotation. This can happen several times if you have a spline that goes up and down a bunch. If your path only needs to travel through a two dimensional space (or nearly so) then you can avoid this twisting by laying it out on the XZ plane and repositioning your camera so that it looks correct. If you are creating a flying piece of ribbon and you want it to twist as it flows through air then use this feature to your advantage and twist away!

Introduction:
Several people have recently asked about ways to create various animations and models that follow a complex path. There is a way to do this using a Loft NURB object whose profiles are placed along a spline using a Tangential Spline animation sequence. Once you understand the basic recipe it is easy to expand and modify this technique to make some very complex structures and convincing animations.

Step One:

Establish a path for your object or profiles to follow or be placed along. This can be any kind of spline - opened or closed and using whatever flavor of algorithm you wish (Hermite, Cubic, Akima, etc...). Make sure that you set the point interpolation to "Uniform" so that there will be even spacing over time of your profiles - otherwise you may get some unusual results.
Create a profile to attach to the spline. In the example below I used a line and later on I use a circle. Use whatever you need to suit your purposes.
Create an animation track for your profile using Geometry->Tangential Spline. Create a sequence. The length will determine how many steps it takes to travel from one end of the spline to the other. Make sure that you use Tangential Spline for the animation sequence - this will properly place the profile on the path.
Create a Loft NURB object and in the Object Manager drag the profile onto the Loft NURB object. Then open the Loft NURB object and using ALT/OPT (Win/Mac) dragging to make enough copies so that you have as many profiles as you need. In the example below I made 5 profiles - later I remade it with 30. Start simple so that you feel comfortable with how this works and then get complex when you understand this process.
Sequentially offset the animation tracks for the profiles so that they create a structure with the Loft NURB object. Just by offsetting them you are spacing them along the path and the Loft NURB does the rest. If there is an odd buckling of the object then you may have a profile out of sequence. Check in the Object Manager and correct if necessary. If there is a twist then this may because your path nearing a perpendicular angle to the XZ plane (see warning above).

5 NURB Lofted splines on a path

Step Two:

If you want to go further and use this process as a modeling aid then please read on...
Once you have all your profiles spaced evenly out along the path you need to remove the Tangential Spline animation data so that the profiles become fixed in space. Do not worry! The profiles will remain where they are based on what point in time the Time Manager is set to.

STOP!
If you do not require that this object remains as a NURB object you can simply use the Structure tool to convert the Lofted NURB object into polygons and not bother with removing the Tangential Spline Data. For this example though - we are going further and want to continue and animate the profiles to create a new and interesting animated NURB structure.

30 Scaled NURB Lofted Splines on a path

Step Three:

With the Tangential Spline animation tracks all removed I went on to create a Scale animation track for the profiles. To make things easy for myself I configured one sequence for the first profile (I added a nice ease on either ends of the scale using the Time Control window) and used ALT/OPT dragging to copy the animation track and sequence to the other profiles.
Then I offset each sequence by 5 frames to create the illusion of the tube expanding along its length - much like a long balloon being inflated.
And that is all there is to it!

Animating the scale of the profiles

Other Resources:

The examples listed above can be easily achieved automatically through the use of Mikael Sterner's Multiple Splineattach plug-in. This is available for a small fee through the PluginCafe web site.