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  04 April 2013


Here is an interesting one ... I have a model of a hatch operated by hydraulic arms. I operate them by rotating one door and by means of symmetry and some aim and parent constraints the whole thing moves with the hydraulics.

However, when I render in the editor viewport it renders ok, but if I render to the picture viewer, the hydraulics have not moved and they stay in the initial position and therefor they protrude through the hatch doors.

Is there a setting I'm supposed to turn on or off? What's going on ...?

Attached Images
File Type: jpg hatch-editor.jpg (51.4 KB, 38 views)
File Type: jpg hatch-picviewer.jpg (38.5 KB, 24 views)
  04 April 2013
Priorities. your going to have to go through your expressions and adjust priorities so things calculate in order to solve right.

Never rely on the viewport renders as it renders what the viewport is already showing, not what calculates properly over time.
Quote: "Until you do what you believe in, how do you know whether you believe in it or not?" -Leo Tolstoy
Kai Pedersen
  04 April 2013
Thanks Kai,

I wasn't familiar with priorities although I've always wandered what they were or how to use them.
After a few trial and error attempts it worked. However, I'm usually not satisfied by doing things without understanding them so I put my thinking cap and tried to make sense of the order in which things should happen.
I take it that and expression not necessarily has to be expresso but simply any 'thinking' process used by Cinema to know what to do.
So let me know whether this is the correct thinking process (please bear with me, I'm a noob)
In this case I had the left door as the object that I voluntarily move. The door drags the piston by parent constraint. The piston and the cylinder are mutually constraint by aim and finally the second door has a mirror constraint with the first door.
So the priority I set was piston 0 (parent and aim), cylinder 1(aim) and right door 2 (mirror).
Is this the way to do it?
(I know that this is probably easier to do it with joints but I haven't got there yet)

Thanks again,
  04 April 2013
There are two tutorials on cineversity I highly recommend to understand the inner workings of C4D's priority system. might be a little out of date in regards to cloth and dynamics, but for the most part it should still be applicable

I really should write an indepth blog post about this since it comes up often.

In terms of expressions, most tags are expressions, so not just xpresso, but target, constraint, IK etc. a few things are calculated after expressions by default, generators and deformers being the key ones. this becomes a challenge as you often need to have an expression come after a generator, like attaching an object to the surface of a generated object. This can cause problems though as generators do not have a priority override like expressions do, so if you want to have a generated object drive an expression and then have that generate a new object the priorities aren't going to work well for you.
Quote: "Until you do what you believe in, how do you know whether you believe in it or not?" -Leo Tolstoy
Kai Pedersen
  04 April 2013
Thanks again Kai,

I will definitely take a look to your tutorials in Cineversity.
This stuff is still very much over my head ...

BTW do you live in Vancouver? I do, and it would be good to know that there's someone so knowledgeable here. I find that there's not much C4D people around here ... is there?

Best regards.
Juan Carreras
  04 April 2013
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