KeyShot Forum

Technical discussions => Animation => Topic started by: BLSmith2112 on July 13, 2016, 07:57:38 am

Title: [Video] Simple Piston Animation. How can I set multiple pivot points?
Post by: BLSmith2112 on July 13, 2016, 07:57:38 am

How can I keyframe the piston to move along with the crankshaft AND the piston head? I tried setting the pivot point to the crank shaft (see video), but the entire piston just rotates as the crank shaft does. A simple rotation won't work I'm assuming, so I'm not sure how to use the program in this manner. Any advice appreciated for this novice.
Title: Re: [Video] Simple Piston Animation. How can I make this smooth?
Post by: Esben Oxholm on July 13, 2016, 08:18:36 am
Hi BLSmith.
Video seems to be private?
Title: Re: [Video] Simple Piston Animation. How can I make this smooth?
Post by: BLSmith2112 on July 13, 2016, 08:23:55 am
That should work now. Any ideas on how to solve this problem?
Title: Re: [Video] Simple Piston Animation. How can I make this smooth?
Post by: BLSmith2112 on July 15, 2016, 06:58:24 am
Not being able to animate this piston will directly effect our decision to buy a license for this software. I have not seen any resources online and geniunely don't know if its possible without having some other third party program that create the true animation.
Title: Re: [Video] Simple Piston Animation. How can I make this smooth?
Post by: Chad Holton on July 15, 2016, 07:05:11 am
What modeling software are you using?
Title: Re: [Video] Simple Piston Animation. How can I set multiple pivot points?
Post by: BLSmith2112 on July 15, 2016, 07:11:33 am
I use  no modeling software. Only Keyshot at the moment. The models are provided to me in .JT file format by engineers. Unfortunately, the only way I have access to these models is through our corporate portal (our engineers use CREO I believe) , and I cannot to get the file in a different format. If Keyshot cannot provide this functionality, what other program lets us animate this?
Title: Re: [Video] Simple Piston Animation. How can I set multiple pivot points?
Post by: Chad Holton on July 15, 2016, 07:50:18 am
This type of animation would be very hard to do in KeyShot alone, maybe impossible. The piston arm motion would be a tough one to pull off.  However, if you can talk with one of the engineers, you can use the FRA file from Creo (basically using Creo to create the animation and sending it to KeyShot). Here's a video that explains the process:


And here's an engine animation using the FRA file from Creo and rendered in KeyShot:

... if you can't get it in different format though, none of this will do you any good as the KeyShot/Creo plugin (loaded inside Creo) is required to do this.
Title: Re: [Video] Simple Piston Animation. How can I set multiple pivot points?
Post by: BLSmith2112 on July 15, 2016, 08:17:06 am
This is the issue. I cannot guarantee that for each engine I need to animate I will be able to get in touch with the engineer who designed it to get them to export specific mechanism information in a timely manner (this is not part of their job description). I need to do this on my own. Any recommendations on my options?
Title: Re: [Video] Simple Piston Animation. How can I set multiple pivot points?
Post by: LayC42 on July 15, 2016, 08:52:23 am
This is the issue. I cannot guarantee that for each engine I need to animate I will be able to get in touch with the engineer who designed it to get them to export specific mechanism information in a timely manner (this is not part of their job description). I need to do this on my own. Any recommendations on my options?

;o) learn creo parametric and export the fra-file to KeyShot. Apply your materials and create a stunning animation. That's all ;o)
Title: Re: [Video] Simple Piston Animation. How can I set multiple pivot points?
Post by: BLSmith2112 on July 15, 2016, 09:08:21 am
This assumes a few things:

Assuming ether is not possible, do I have any other options? Otherwise, I do have After Effects + Element 3D that I can animate in.
Title: Re: [Video] Simple Piston Animation. How can I set multiple pivot points?
Post by: Chad Holton on July 15, 2016, 09:15:31 am
Not sure what other programs will import JT format to give a recommendation. Too bad you don't have access to OBJ files instead...
Title: Re: [Video] Simple Piston Animation. How can I set multiple pivot points?
Post by: LayC42 on July 16, 2016, 12:37:15 pm
The simplest solution is to use creo mechanisms with export as fra-file. Creo can export jt files but the license for this interface is very expensive!
You can use step, iges, obj (wavefront), x_t (parasolid) or bip with the plugin. But every file format doesn't support the connection you need.
Title: Re: [Video] Simple Piston Animation. How can I set multiple pivot points?
Post by: HaroldL on July 16, 2016, 04:10:03 pm
. . .How can I keyframe the piston to move along with the crankshaft AND the piston head? I tried setting the pivot point to the crank shaft (see video), but the entire piston just rotates as the crank shaft does. A simple rotation won't work I'm assuming, so I'm not sure how to use the program in this manner. Any advice appreciated for this novice.
BL, It helps if you think about the actual motion of the parts different from how an engine actually works. If at all possible it is best to start this with the  piston at either TDC of BDC to make the calculations easier.
1. Apply a 360 degree Rotation Anim to the crank shaft.
2. Apply a Translation Anim to the piston so, if starting at BDC, it moves up and another Translation to move it down. Both translations should be equal to the stroke.
3. Apply three Rotation Anims to the con-rod. Think of it as a pendulum in this case, oscillating back and forth with the wrist pin as the pivot. You need to calculate the angle of con-rod oscillation based on the con-rod length and the stroke. The first Rotation will swing the con-rod to the side a calculated distance equal to 1/2 the stroke. The next rotation will swing it back the opposite direction a distance equal to the full stroke. The third rotation will change the direction again, 1/2 the stroke, back to the beginning. You will need to apply some Ease-In, Ease-Out and Ease-In/Out to these rotations so they will appear to stay in step with the crank shaft.
4. Either apply 2 translation anims to the con-rod or paste Linked animations from the piston. This is so the con-rod will move up and down with the piston while is oscillates.
The ease-in/out method does not work accurately though. Some times it appears that it is too soon or too late in the timing of the parts. It would be nice if there was some kind and easing adjustment that you could make to tweak the motion a little.

After all this work you may be able  to get a half-fast animation.


I worked up an animation on a simple engine model just to prove out my method (the preview is attached).


I think KeyShot is a great rendering program but until there are some animation enhancements, for me, some of the shine is beginning to wearing off its animation capability.

What would be real nice is if it would respect the CAD programs constraints.