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sasasa741

How to slide along constraint axis, not to world?

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Hello, question is simple but I couldnt figure out how to solve this.

I am trying to make car suspansion mesh. The meshes that are bottom are connected to the wheel. Above meshes are gonna be suspension mesh. I connected them with "connect adjacent pieces"

image.thumb.png.a61778689ed0fb614b9d08020db4ac51.png

In my dopnet, I have "constraint network" with "slider constraint relationship"

But unfortunately, slide axis is depend on world axis, not constraint axis. It makes me sad HOW HOUDINI does not have option that I can use constraint axis...

image.thumb.png.c6ec801c6d1969cd777f9abff89c9f3e.png

 

Because of that, when I rotate car, that 4 constraints move too, but in Dop net, slide way isnt change. See the image bellow:

image.thumb.png.d0ae87ae1868c8cce95fef3ec6adbc50.png

 

SO, this issue is not just for slide constraint, same with cone twist axis too. 

 

There are two way to fix this;

1. option is, I am not gonna change position&rotation of my object in sub network (which is car). BUT How can I change it in DOP network? There is no "translate node" in Dop. (There is "position" node but it doesnt work like "translate" node)

2. Option is, "slider constrait relationship" node must have my constraint axis data. 

 

How can I do that?

 

I have thousands of problems, this is just one of them.. :D THANKS !!

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If I remember correctly those settings are in local space, however that's defined by orient or r attribute, which if doesn't exist is computed on initial frame and therefore it may seem global on that frame and obviously misaligned for following frames, so make sure you manage orient on your packed geo and constraints in sops properly

I'd also suggest completely avoiding DOP level constraint controls and control them using attributes living on your constraint geo that constraint network is using

List of common constraint attributes and some more info here 

https://www.sidefx.com/docs/houdini/nodes/dop/constraintnetwork.html#attributes

 

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15 hours ago, anim said:

If I remember correctly those settings are in local space, however that's defined by orient or r attribute, which if doesn't exist is computed on initial frame and therefore it may seem global on that frame and obviously misaligned for following frames, so make sure you manage orient on your packed geo and constraints in sops properly

I'd also suggest completely avoiding DOP level constraint controls and control them using attributes living on your constraint geo that constraint network is using

List of common constraint attributes and some more info here 

https://www.sidefx.com/docs/houdini/nodes/dop/constraintnetwork.html#attributes

 

I tried to create vector attribute of constraint, and I sent it to the "goal hingle axis" of "slider constraint node. but it didnt read it. same way with this video. But didnt work. 

 

So, I have no choice other than translating the enviroment, not translating my car..

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On 2/14/2021 at 5:51 AM, sasasa741 said:

So, I have no choice other than translating the enviroment, not translating my car..

Or you can try using p@orient point attribute on your constraints as mentioned to define your local space, then translating your car (as packed end) would naturally transform the orient attrib as by default it's a quaternion 

While I have not used slider constraints, I've been able to successfully use soft constraints with single axis of freedom for suspension type constraints, however I don't imagine slider being any different

 

 

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12 hours ago, anim said:

Or you can try using p@orient point attribute on your constraints as mentioned to define your local space, then translating your car (as packed end) would naturally transform the orient attrib as by default it's a quaternion 

While I have not used slider constraints, I've been able to successfully use soft constraints with single axis of freedom for suspension type constraints, however I don't imagine slider being any different

 

 

How can you use soft constraint for single axis, for example for axis of constraint? 

 

I have big problem to make car dynamic rig.. My houdini is not stable..

 

I can connect wheel to the body without doors, windows. It works, but when add doors, simulation explodes. (believe me, even all constraints are all fine) Or when I translate car above a little bit, everything freaks out. This program is not stable at all. Or mine has problems. 

another example I am having, When I set constraint iterations 200, it works well, but when I make it 201 or 199, simulation becomes trash. Same with substeps. It doesnt do what it supposed to do. 

I just want to make a car, so I can use it for front crash, or throw it from cliff, or something else. But it is impossible. 

 

 

Edited by sasasa741

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20 hours ago, sasasa741 said:

How can you use soft constraint for single axis, for example for axis of constraint? 

You can use i@condof and v@condir from the attribs I pointed you to to limit degrees of freedom for constraint

20 hours ago, sasasa741 said:

I can connect wheel to the body without doors, windows. It works, but when add doors, simulation explodes.

Not sure if this is your reason for exploding, but make sure all your constraint lines have 0 length, e.g. both points of each constraint line are on the same position

 There is not many constraints which can afford to have misaligned anchors, mostly Glue, Spring and Soft, for all others I'd definitely avoid that 

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