Cineversity

Hi

Im making a fishing rod that cast a line.  I got as far as making the rod spline with spline dynamics, and hair constraints between the rod tip and weight.  I have the spring set up also.

What is happening is that the spline hair constraint is not fixed in place during animation, it keeps leaving its position its constrained too.  I tried cache what I see needs caching, but no setting works?

https://www.dropbox.com/s/lwr98evq44k5iwb/fishing rod dynamic loosing constraint.zip?dl=0

Thanks

Post #6 (sorry about the weird order, the forum’s software is nuts at the moment.)
P.S.: I wasn’t certain if the camera set up was clear, so I made a short 60 second screen cast. I hope it supports this discussion.

Clip (can be downloaded)
https://www.amazon.com/clouddrive/share/wKHTm9EfTDtWUQYrQgOMKbaUWPp36kGP3JGfXgxf1yI

I have set up a second camera, which is not the file above, but just to showcase both ends of the spline and how it holds its constrained position. Which is, after all the target of this forum’s thread.

ENJOY

Post #1 = reply to the thread opening post which would be Post #0

Hi rectro30,

Please have a look at the file and render a preview with the “Camera.work”.

Scene file
https://www.amazon.com/clouddrive/share/aPzR3G76TCInxw2lbXFhNnBXiPBladSaiyddX1VAhdR

What happened in the file you shared is a typical Priority problem.

The information processing simplified said, works from the top in the Object Manager down to the last object. there is more; please check out Kai’s tutorial about it.
https://www.cineversity.com/vidplaylist/advanced_constraints/expression_priorities_part_i
Or just use the content here
https://help.maxon.net/us/#TTARGETEXPRESSION-OBASELIST

This is critical; any information that wasn’t processed so far in the frame is not available, but the data from the frame before. Worse case, several of those “frames before” information is used. This can lead to two or three perhaps more frames of visual “delay” in the scene.

So the position of your objects was just leading to such a delay.

All the best

Thanks for the reply and file.  I loaded the file and dont understand what Im looking at? 

I always thought the priority was from the bottom up, not top down.  In either case I moved the Sweep with the spline within it to the top along with the object thats constrained to the end of the spline to the top, the same thing happends, there is no priority change here that has fixed the constraints to remain in place. I initialy thought it was a priority issue and move found no priority settings for the hair constaint, neither was adding a priority tag making any difference.  As you know the red line shows just how much the constained objects have moved from their set position (see image)

https://i.imgur.com/x1xNX6S.jpg

Dan

Post #3

Hi Dan,

From top to bottom, the bottom is processed last.

The camera is a child of the Line Holder, the place where the problem is. This helps to focus on the issue as the problem stays in the center of the frame. In my preview, it stayed in place. (I had shorty file: _01.c4d up, please make sure that you check out file …_02.c4d)
Preview:
https://www.amazon.com/clouddrive/share/SS80Qlf9lfB932iLLNtRCcufXerBWmllEvmbdgeLQuw
There is no gap anymore as in the setup I have received.

If you move the Sweep to the top, you create an even worse situation: Nothing has been processed so far other than the Sweep. So any information that the parts of the Sweep set up receive might be a “frame+” old. Please note that anything you see in the Editor’s view is a product of several refreshes per frame, perhaps, and it might hide some problems; hence the preview renders, as the render calculates and only one time per frame.

The object that needs the most information from the scene and doesn’t share any information with anything, as the Sweep does here, should be in the lowest position and not under a parent; here, the Priority settings might create an exception.

To just move one single element around ignores the core problem. Compare the scene file that I have sent back and yours; there are more changes.

Example: The Spring moves the Platonic around. So, check alone the information flow here. Priority is not alone in the setup of numbers.

The priority requires more than just the Object Manager hierarchy; it also has other influences, hence my suggestions to check out Kai’s tutorial and the Help Content. There is no shortcut, sorry.

Often the suggestion is to bake or cache the information. Also, here if you cache and bake in the wrong order, nothing will be solved/changed.

As a side note: If the setup was precise, the Constrain>Tag>Offset value might be ignored, but for this scene, one should use anything way lower than 100%.

All the best

Thanks I will have to read through this a few times, and read the link you posted, it gets confusing a tad.  Is this a issue in all 3d software that perform dynamics, or is it something Maxon just needs to sort out?

Thanks, Dan

Post #5

Dan, this is certainly something with a learning curve, and yes, sharing Cinema 4D information/knowledge in my second decade has shown me that this is one of the most ignored parts.

I haven’t compared other applications in public, and I will not start here.  I have used my first 3D app (Archicad) around 25 years ago and have used several since; none of them had a magical fix for priorities.

What you can do, google “Priority” + “the name of a 3D app”, and you might get your answer.

All the best

Post #6 is above; sorry about the confusing order, but the Forum’s clock/date seems to be nuts.

Post #7 The time stamps of the forum seems to be updated but the sequence stays as before.

P.S.: here is a clip and a file, showcasing that the wrong order in the object manager can have a “domino” like effect in terms of “delay”.

The same objects are then used in comparison in a working order.

Clip (60 seconds) and scene file:
https://www.amazon.com/clouddrive/share/407HU8yncShJIYw0VQpsoiT464AdiFj7RY1uATk5Ub5

I added this extra information to your initial question, but also to a forum’s thread, as it certainly is something that can’t be stressed enough.

Cheers

Thank you, thats very good of you to put the extra time to help me.  I will look at this in detail tomorrow.

Thanks, Dan

Post #9

You’re very welcome, Dan.

Once those kind of internal “information flows” will become familiar, at least for me, things have more clarity and with it, they are even more pleasurable.

Enjoy.

Hi

I understand Order Of Operation, iv been familiar with this since about 6 years ago in MODO, however to having to work out what every single step C4D takes for every single item in a scene so it renders correct is in short mind blowing.  My scene is, should be simple, yet Im looking at my scene swapping around the order of my objects to what I feel needs priority and no matter what I do that red line/gap between the spline and line holder remains.  Should I have to cache the Platonic meshes ridgid body, spline dynamics to see the outcome in the view port, could you fit my scene so I can see what it is im doing wrong please?  Maybe im tired and just need a break from it.

Dan

Post #13

Hi Dan,

1 Joint-Rig set the initial motion
2 The spring uses this motion
3 Spring creates the Platonic motion
4 Platonic delivers to Spline.

Sounds reasonable to me, to sort this out.
Yes, there are more complex set ups, and it is not a walk in the park to go through those, as in a complete biped rig.

Enjoy

I think some of my problem is the inconsistent feedback Im getting in the view port.  Id assume that if I cached the spline dynamics and the Bake All option for the platonic that I could scrub through the frames and get the same results, but I dont, so I assumed the order was wrong, even the order you listed as correct.

Thanks, Dan

Post #11

Dan, as I always say, there are not problems, mistakes, etc., only added experience.

Having said that, your input leads to a closer look at “inner mechanics”, and I guess that is true for all apps.

In the editor view, you will see a more frequent update of the content. Each click that changes something will trigger an editor view update; otherwise, you wouldn’t get feedback on what just happen.
This new update can now access data from all parts already calculated and doesn’t lead to use information from a previous frame. In that way, things sometimes look better in this view than in the rendering.
Like in the last clip I shared, I frequently use the “a” key to refresh the viewport. Each time the scene gets calculated, the “red” Tori moves one after the next into the “expected” position.

While the rendering starts, this isn’t done anymore; the application goes one time through the given information and then moves on.

It is easy to imagine that we create a feedback loop, where the movement from one object influences the next, and the next object itself moves the previous object. If we had an “automatic” solve to that, the app would have to go endlessly through this, not knowing when to stop. … and yet, some objects have two priorities as they need to do something and then wait for an action to happen before they move on. If all of that could be fixed quickly, the question would remain, how can any app know what the artist wants in the first place, e.g., if priorities are equal. The result might not be desired.

Then (as you mentioned, scrub through), some parts of a scene build upon all previous frames, like dynamics, particles, etc. If that information is not given, frame by frame, i.e., not cached, the scrubbing results in a fragmented “something. The MoGraph Tracer is an excellent example to see that in action, that scrubbing isn’t working, and there is no cache for that either.

Anyway, if there would be a possible solution, it would have been done without taking artistic decisions away.

I hope that the discussion here and the examples will help to sort things out in the future. Often a little piece of paper and a short diagram might help to get this streamlined.

After all, if things do not produce a problem in the render, nothing needs to be fixed.|

My best wishes

Why are the red post (reply) numbers?

The forum’s software seems to show (for whatever reason) a hick up, and times got messed up. Really sorry about that.