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Grouped object containing hair in an Emitter - problems with too much or no dynamics.

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Paul Davies
Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 15, 2018 at 12:06:28 pm

Hi everyone,
im making a scene for fun of some troll dolls being emmited down into a bowl and want them to pile up and for their hair to move and interact with objects hitting them. HOWEVER, when i make the group dynamic like a collider object, the eyes and hair explode off as they interact with the body. When i switch off the "self collisions" in the tag, it just makes it one big grouped object and the hair is rigid and doesn't move at all.

Hoping someone can shed light on it for me.

Thanks!


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Brian Jones
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 17, 2018 at 3:12:45 am

eyes are a child of the head or all parts as a child of a null? Either way you should be able to change the Collision/Inherit Tag setting of the dynamic body tag to Compound Collision Shape with Individual Elements - Off to keep the eyes from exploding out. How are you doing the hair?


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Paul Davies
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 17, 2018 at 3:58:12 am

Hi Brian,
The parts are Emitter_Null (with tag)_troll,eyes,irises,plate,hair object.
the troll is in a null, body is separate to a plate i used to make the hair object, eyes have two parts to them.
All inside the null with the dynamic tag on the null.

I have brushed the hair and arranged it the way i want (standing up like trolls hair) and was hoping it would go wavy as it fell through the air and hit other objects. But it currently goes stiff as a board. and also goes through the floor.

Cheers


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Brian Jones
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 17, 2018 at 8:37:06 pm

this seems to work for me. Very simplified but the general structure should work. Only the 'head' gets a tag (Compound Collision Shape, no Inherit) the 'eyes' and hair are children of that. The eyes are that massive only because I wanted to make sure they were included properly in the collision calculations and you might not even need a compound collision shape if the eyes aren't going to be bouncing off things (I've seen various versions of the dolls and don't know what yours look like).
Putting a hair collide tag on the floor worked fine but when I tried it on the hemisphere it broke the hair until I made the hemisphere editable and reversed the normals.

12553_trolltrial.c4d.zip


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Paul Davies
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 17, 2018 at 11:02:01 pm

Wow, thanks for that! I will put the heirarchy the same way and give it a shot.


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Paul Davies
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 17, 2018 at 11:23:09 pm

Hi Brian, I'm still have trouble with the hair - i think it;s because i brushed it to a specific shape and set as dynamics. But i don't see why that would mean it wouldn't move at all after that.

im attempting to use the upload file button here...
(i dont know how this website works, it has an upload button and then sends me out of the thread, so iv'e tried posting the same thing twice but not sure where it is popping up.... doh!

here's a link to the file - maybe that will work. 12554_trollfall.c4d.zip


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Brian Jones
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 18, 2018 at 4:50:43 am

you can get the hair to stay as it's styled by checking Rigid in the Hair/Dynamics tab *but* you are going to have trouble with the hair and other objects with dynamics involved. Limit the emitter to a single troll (don't select Rigid yet) and select the hair object and watch what happens, it falls like it's not moving because it isn't - not in it's own 'hair space' anyway (and as the single troll falls into view it's hair will be doing exactly the same thing). You can get hair to react to dynamic objects but you can't get the dynamic objects to react to hair, their dynamic systems are not related. At least I think it's not possible with hair guides since the hair isn't really there (so to speak, it's a volumetric render of splines). Testing, the only thing I could do was Generate in the hair object as Flat (or any of the poly hair probably but Flat will be quickest) and that would react like a solid and stop the object from rotating the hair through the bowl. Getting that to look soft might be possible but more testing is going to have to wait until tomorrow.


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Paul Davies
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 18, 2018 at 5:30:23 am

Hmm, I was wondering whether it would work to have a joint chain out the top of the head along a spline and constrain the hair to that? Then i'm guessing the joint chain would interact with the other dynamic objects normally? and if the hair is following the joints, maybe it will just look like its interacting with other objects.


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Brian Jones
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 18, 2018 at 6:33:27 pm

the problem would be that the joint/spline chain also has no real polys so wont react to collisions (I would think) but if you had geometry in the hair (I assume invisible) that got the hair to flex with it . I've had some success with separate objects with hair that is generated polygons but as before the hair will bounce with the object impacting something and will stop the whole object from rotating but doesn't deform in response to hitting something itself. i.e. object hits floor hair attached to object bounces but if hair hits floor first, it collides but does not deform. Settings are really touchy with this as well, it's easy to get 'explosions' due to the interaction of dynamics and hair dynamics.

12563_trolltrial2.c4d.zip


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Paul Davies
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 18, 2018 at 10:54:06 pm

Have you seen this tutorial by Chris Schmidt? When i saw it i thought maybe it would work?



Maybe if there is an object like Chris's chains or a few sort of stiff chains in a similar shape to the hair, then they would frm a loose cage for objects to hit. It seems a bit of overkill though.

I just downloaded your file and looking now.


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Brian Jones
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 19, 2018 at 10:25:04 pm
Last Edited By Brian Jones on Jul 19, 2018 at 10:26:00 pm

I'm still testing but this looks promising https://greyscalegorilla.com/tutorials/how-to-make-a-low-poly-mesh-for-soft... -- create the hair as polys (Generate/Flat) and do a cage around it and soft body it - not like in the video, totally soft but soft-ish. It would require a connector and maybe it's too complex.... ah, maybe cage the entire troll, hair and all and use vertex weights to make it flexible only for the hair... going to test more at home where I have some more horse power


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Paul Davies
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 20, 2018 at 4:35:17 am

That does look good - I guess I would like to make the hair look as good as possible, so making it flat like in your previous file won't really be able to render in a photorealistic fashion would it? I feel like the guides need to be restricted to a spline (splineguide plugin maybe) and then use that spline to control a cage like you are suggesting. I haven't had a chance to work on it the last day or two - i did a turntable render to show the model off and hopefully the falling troll will be the next step.


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Brian Jones
Re: Grouped object containing hair in an Emitter - problems with too much or no dynamics.
on Jul 20, 2018 at 4:59:09 pm

the look of the hair as polys is dependant on the material you put on. Since troll hair is some form of plastic (I assume) and the hair mat is trying for human hair it's likely a good material will get you there just as well, it's also possible that one of the other hair generate shapes will give a better look and with the cage method the number of polys (which is why I was testing with flat with the earlier tests) is less crucial as a performance hit


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