Spline vs Linear



  • So, I've been making a few random things in poser, and something I've noticed is that the Spline section thing (which it sets the keyframes to as default) never seems to work. I made an animation of someone falling over and they sort of jumped first. When I swap it to linear it all works fine. I sort of understand why this is, but I just want to know what the purpose of the Spline section is, because it just seems to get in my way. On a side note, is there a way to set the sections to Linear as default.

    Side-side note. Sorry if this makes no sense, I'm really guessing how all these 3-D terms work.


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    Spline interpolation smooths out the transition between keyframes in a fluid natural manner. Linear tends to look robotic and mechanical.

    I don't know of any way to set linear as the default, but if you set the first keyframe to linear, then as you add keys they will all be linear until/unless you change it.



  • But why does it go like, beyond the point?

    Not very helpful diagram:

    a--------b--c-----d

    So, I could see if I wanted it to go from a to c, it went past b halfway through and sort of slowed down, like accelerating and decelerating. But when I do it, it seems to go past d, which, I really don't want it to do. I keep having maybe a small camera pan, and it turns into a sort of roller-coaster view-point with the spline on.



  • @pip.jr As far as I can tell, spline averages and smooths the motion over all key frames. Not between key frame A and key frame B, then key frame B and key frame C, and finally between key frame C and D.

    Let's take a simple head nod. Start with the head neutral at bend = 0. Create a key frame. move about 30 frames and create a new key frame. then bend the head up to about bend = -25. Then advance 30 frames, make a new key, and return the head to bend = 0. Advance another 30 frames, key frame, and make it bend = 25.

    This is just an example of what I'm talking about by the way. I haven't actually tested this specific animation.

    If you play this animation, then I'm guessing you will get exactly the kind of behavior you are talking about. Because Poser is not smoothing the motion between 0 and -25, then -25 to 0, and finally between 0 and 25. Instead it's smoothing the motion between -25 and 25. So yes, in between certain key frames the motion is not going to be what you expected.

    Keep in mind that this is not meant to be a technical description. It's my personal attempt to explain what I've seen occur.

    And yes, I basically find that spline is completely useless because of this. Unless you break every animation up into multiple mini animations and then splice them together afterwards in another piece of software.



  • https://forum.smithmicro.com/topic/483/help-a-newbie-out

    Above is a link to a post I did here that refers back to Runtime DNA. Look for my post and click the links and that will take you to a explanation of the Spline curve and basically how it works.

    I really need to get the PDF of animation in poser done so I don't have to keep sending people to RDNA as I do not know how much longer the information will be at RDNA.


  • Poser Ambassadors

    @pip.jr said in Spline vs Linear:

    But why does it go like, beyond the point?

    Not very helpful diagram:

    a--------b--c-----d

    So, I could see if I wanted it to go from a to c, it went past b halfway through and sort of slowed down, like accelerating and decelerating. But when I do it, it seems to go past d, which, I really don't want it to do. I keep having maybe a small camera pan, and it turns into a sort of roller-coaster view-point with the spline on.

    You can always set a spline break at d, so it will not go beyond that.
    A more fluent solution is the add key frames in the graph editor and move them up and down to get a more fluent motion as you want it



  • Spline animation has many benefits. The first being that nothing instantly accelerates or just stops more often than not.
    And then there is the number of keyframes needed.
    Smooth Linear graphs (actual smooth playback) usually ends up with more key frames than the Spline approach.

    I usually use Spline Breaks for impact of centers, constraints, physics, etc, which is usually the better way to go about it.
    But Spline animation using breaks uses a very different workflow from Linear animation.
    3 Spline keyframes in a row gives a more flexible approach than Spline breaks, and allows you to modify the spline curve as well.
    Obviously there are times you may want to use a spline break as well.

    The fastest way to learn Spline animation is to start it as linear, then edit the graphs to remove as many linear keyframes as possible.
    That will give you the smoothest looking animations, for the most part.
    Once you add the linear keyframes, a pattern will show in the graph that can be done simpler and more fluid with Splines.
    Start with the hip, then work your way out. Look for obvious spikes that are not necessary.
    (some are, as you will find out while removing key frames.)

    Poser also allows you to have animation layers, that are turned off.
    It is very handy to be able to see where you came from in a few layer clicks.

    Poser has a feature called Resample Keyframes, use it sparingly and only on small sections of time until you get the knack of trimming out keyframes that way. You can get really odd results from it. Very few animations can be converted to a single keyframe stepping and not loose something really important.

    Read this, it touches on more.

    Splines and Animation

    The disadvantage of linear animation is when trying to stitch together animation sets, such as in a video game. In a video game, the Character could have a few hundred animations that get put together to make it appear fluid. With Linear, if there is a drastic difference from one pose to the next, a lot can look very odd. If the animations were planned out using a Spline approach, they fit together and mix much better. More so when animation mixing is used, and Poser can do that as well.
    If the two animations you are mixing have harsh changes, well, you end up with two harsh ones if the are not on the same frame.

    Read this, this isn't so easy to do in Linear unless you use a lot of keyframes to do so. Things like arc, follow thru, etc, fall right into place with Spline animation, to a point.

    Disney Animation: 12 Principles

    As with any animation, save it a lot, sequentially as well.
    If you miss a change because a layer was off, etc, you have another file save to go back too.

    Hope this helps.