how to make CG slime

[jiboren]

hi guys:

i am working on a monster project now which have a shot that the monster roar to the camera right,what i need to do is add some CG slime in the monster's mouth,some hang in and some fly out while it's roaring.

i reference two movies,one is avatar,the creature in it has some wire mucus in mouth when it roar to the actor,what i think maybe wire solver in houdini can finish this,and i tried ,but the result not looks so good,maybe because of some parameters,the result looks like some rubber band.

the other movie i referenced is pirates of the caribbean 2,at the end the octopus roar to jack ,lots of slime/mucus spray out to him,looks like egg's liquid. this kind of slime difficult to me,but perfect to my project .

hmm^ any ideas,suggestions welcome.

thanks

cheers

rjb.

Edited April 10, 2011 by jiboren

[Eitht]

Hey jiboren,

first thing i would go to is FLIP fluid because it's the only thing i've played with after watching 'Intro to FLIP' video. Checkbox called 'Sticky' which kinda makes them sticks to object upon collision & it feels like the particles also glue closer together. Reopened the file and attempted to get a slime look, the setup is still very close to the one while following Jeff Lait. Here's the file incase you don't want to make it from scratch.

Not sure if it's an overkill to use FLIP, hopefully better solutions come by soon.

Good luck!

eitht.

FLIP_slime.hipnc

Edited April 10, 2011 by Eitht

[jiboren]

Hey jiboren,

first thing i would go to is FLIP fluid because it's the only thing i've played with after watching 'Intro to FLIP' video. Checkbox called 'Sticky' which kinda makes them sticks to object upon collision & it feels like the particles also glue closer together. Reopened the file and attempted to get a slime look, the setup is still very close to the one while following Jeff Lait. Here's the file incase you don't want to make it from scratch.

Not sure if it's an overkill to use FLIP, hopefully better solutions come by soon.

Good luck!

eitht.

Hi Eitht,

thanks for your reply,but i am sorry that was not i want,i found some pics from google,i upload them here,maybe you can clearly about what i need to try.

a little like play egg mucus:

for example,stick between the teeth and the mouth or tongue,move with the open mouth motion,will disconnect/break once the mouth open too much,will shakeing and bending when air force come out from the creature's mouth,

[old school]

I would try wires as one try for this then surface with Particle Fluid Surface SOP.

Particle Fluid Surface SOP only needs points and pscale attribute for the radius to surface. This means you can merge in points from anywhere and then surface them. Points from SPH, FLIP, scattered points on surface of SDF from liquid sim, user-supplied points from SOPs, etc.

For the surfacing of the strands, convert wires to tubes with shaping controls and scatter points or whatever then Particle Fluid Surface the points.

You can also use Cloth solver, thin strands of cloth as cloth supports changing topology over time. Opens up the door to SOP Solver geometry modifications. Keep the geometry simple for speed.

Wires and Cloth work very well with noisy wind forces so when your creature bellows, you can put a fan in there and blow away at the wires/cloth. If you use cloth, you can even have the pieces break if the force gets too large and you go beyond the stretch threshold for tearing.

[Eitht]

Sounds like a really cool thing to have in a portfolio, mucus blown out from a monster reminds me of jurassic park where the little girl reached out to touch long-neck!

I am tempted to try it after reading oldschool's suggestions. o_o

All the best!

eitht.

Edited April 10, 2011 by Eitht

[jiboren]

I would try wires as one try for this then surface with Particle Fluid Surface SOP.

Particle Fluid Surface SOP only needs points and pscale attribute for the radius to surface. This means you can merge in points from anywhere and then surface them. Points from SPH, FLIP, scattered points on surface of SDF from liquid sim, user-supplied points from SOPs, etc.

For the surfacing of the strands, convert wires to tubes with shaping controls and scatter points or whatever then Particle Fluid Surface the points.

You can also use Cloth solver, thin strands of cloth as cloth supports changing topology over time. Opens up the door to SOP Solver geometry modifications. Keep the geometry simple for speed.

Wires and Cloth work very well with noisy wind forces so when your creature bellows, you can put a fan in there and blow away at the wires/cloth. If you use cloth, you can even have the pieces break if the force gets too large and you go beyond the stretch threshold for tearing.

thanks old school.

hmm,same way as i did before.

yes,i tried wire solver,group some point in the mouth and connect them as line use addSOP,then sim them in dopnetwork as wire objects,append pin constraint to the wire,also put a fanDOP force in the throat and keyframe/noise expression it,try to match the creature's roar motion,after that use dopimport the wire to sop and do resample ,create pscale attri,copy metaball or pSurface it,but unfortunately my version looks like rubber band ,

i am not use cloth because of the speed of houdini's cloth,but i will try if i can get a good control tomorrow ,my guess the tearing function of it maybe can give me a good result.maybe i can combine the wire way and cloth way together

i will keep trying on this,if you have other good ideas don't forget to tell me

thanks guys,

best

you friend.

[jiboren]

hey ,just curious after my post,maybe we can discuss this further that how to do the effect in pirates of the caribbean 2 which at the end the octopus surround the ship and open mouth with many teeth, then spray a lot of mucus to Johnny Depp ,perfect mucus,hehe ,my guess they shot a lot of practical mucus maybe.but if possible to do this in houdini or other software.

,

[Macha]

How about use particles with copied metaballs. For some gooey behavior turn the creature's v vectors into a vel volume and use it to advect the particles. Or turn the creature into a smoke emitting particle system (or just add it's v to an existing smoke sim) and use that to advect.

[Sean Lewkiw]

I had to do this about 8(!) years ago. Here's how I'd do it, using the same method.

I'd take points on the mouth, join them by an add sop, resample. Using a ramp or chf function, make them red in the middle and black where it touches the mouth. Send to dops with lag and overshoot multed by Cd.r so it only flaps around in the middle and stays stuck to the lips, you can mult in some noise to get animated slime due to shouting or something at this point. Back in SOPs, polywire with $CR as width so you get thin strands in the middle and thick where it touches the mouth. If that's all you want, you're done and it's easy!

If you want them to break and fly out, add some kind of velocity attribute. Use a carve sop to break the two lines into two prims before they go to chops. Back in chops, use this as a trigger to add transform info when the trigger happens. Use your width attribute to mult the lag. Now take the vel vector and use this as a mult to add some fraction of a transform to the original point pos after the trigger. You can get them to break, detach, or form (as drips), or even birth drips off each master drip using some combos of all these methods. You will end up with a hella-complex chop network, but this is completely controllable with no simming.

[jiboren]

How about use particles with copied metaballs. For some gooey behavior turn the creature's v vectors into a vel volume and use it to advect the particles. Or turn the creature into a smoke emitting particle system (or just add it's v to an existing smoke sim) and use that to advect.

hi,so lucky that i have a chance to ask Bill George, the vfx supervisor of pirates of caribbeans 2,amazing guys,he told me that the octopus roar to Jack the slime did by fluid sim, when the cam turn to shot his face the slime stuck on his face that did by practical things and also add some CG slime fly through the cam to enhance the effect.

[jiboren]

I had to do this about 8(!) years ago. Here's how I'd do it, using the same method.

I'd take points on the mouth, join them by an add sop, resample. Using a ramp or chf function, make them red in the middle and black where it touches the mouth. Send to dops with lag and overshoot multed by Cd.r so it only flaps around in the middle and stays stuck to the lips, you can mult in some noise to get animated slime due to shouting or something at this point. Back in SOPs, polywire with $CR as width so you get thin strands in the middle and thick where it touches the mouth. If that's all you want, you're done and it's easy!

If you want them to break and fly out, add some kind of velocity attribute. Use a carve sop to break the two lines into two prims before they go to chops. Back in chops, use this as a trigger to add transform info when the trigger happens. Use your width attribute to mult the lag. Now take the vel vector and use this as a mult to add some fraction of a transform to the original point pos after the trigger. You can get them to break, detach, or form (as drips), or even birth drips off each master drip using some combos of all these methods. You will end up with a hella-complex chop network, but this is completely controllable with no simming.

cool chop ways,about my project,finally i finished the slime by springSOP,i found some times use sop or chop can solve big problems,i am working on a taser gun proj recently , when the barb comes out from the gun followed by a metal wire which should looks like some sin function curve,first i want to try dop wire but then i use vop to add sin deform and measure the length of each segment and mult it to the sin amplitude,so the metal sinc wire can stretch and relax easily.

Edited May 15, 2011 by jiboren