Wax melting, candle burning

[tious13]

candle_001.avi

 

 

Hi, I'm trying to setup a candle melting in houdini using Flip with variable viscosity but I'm  facing a couple of issues. 

The cold wax has a viscosity of 1.10^6 whereas the hot wax has a viscosity of 10.
First issue: my hot wax always drags the cold one, how can I litteraly freeze the cold wax?

I also would like the wax to be slightly pushed toward the center of the scene to always slide against the candle. But applying such force makes the wax go up due to the contraction (don't know if I make sence).
Is there a way to aply force to a specific area ? I don't know how to use "mask field", and can't acces the exemple in the doc :/. Is It possible to do something like that:
"If temp>50 + 5F then apply force"  meaning waiting 5F after the temperature reaches the desired treshold to apply the force?

I also would like to kill some particles like 20% when they reach a temperature treshold, how can I do such effect in dop ? sop? pop ?  I have absolutly no clue.

Then for the fire "room" (right next to the flame) I would like to use a vdb combine in substract but can't make it work « more A grids than B grids », can you enlighten me ?

 

And last but not least I have some collisin issues with the chandelier, I might not be using the correct method. Once again what is the best way to you to get clean collisions?

  

Thank you for your help 

candle.zip

[alksndr]

Try the file I posted here for some of those issues - http://forums.odforce.net/topic/23904-melting-flip/

 

Will let you select particles and apply whatever you want, so that can solve the freezing killing and force etc. For collisions try volume based with higher res. Cant open houdini rn but ill try to check out the vdb thing later 

 

Hope it helps!

[Farmfield]

For the base you just need to up vescosity untill you get a solid, but for the melting part, you probably need to do a setup where the vax melts later, but faster, but make it solidify later, slower... That's the weird thing with candlewax, it's hard all the way up to the point where it just melts and becomes almost like water, but then it takes a long time to cool down. It's basically a bad heat exchanger.

[tious13]

@alksndr
thanks for the link, I've studied your hip file and I don't really see how it can help with the "drag" effect. I see that you set all the velocities to 0 when the particle reaches y- but the still get pushed by the other ones. Wich is what I try to avoid. I didn't have the time to test it on my hip file though so, I will try that tomorrow

 

@Farmfield

Even with a very high viscosity I still get some bending/dragging, its never really a solid. Maybe I should up the viscosity more but it seems to "cap" at some point, never truly getting solid. And you are totally right about the heat exchange. I was planning to use my setup for a timelapse effect, thus avoiding this tricky part of getting the perfect heating/colling/rate

 

basically I would like to tell my liquid particles that they have no other choice than going around the solid ones, and he solid ones that whatever happens they cant move the slightest


 

[Farmfield]

You gotta up the values, this is a flip sim.

 

[tious13]

Alright I'll crank the value waaaaay up ,  any advice how to delete the particles ? And the vdb combine issue ? 
Ill post a playblast with a f*ckingly high viscosity soon 

[tious13]

When upping the viscosity the wax still get pushed away and I get some nice fireworks too   
 

visscosity.mov

Edited December 4, 2015 by tious13

[alksndr]

Hmm so from your original image, you want the blue particles to be moving but the black ones to be frozen and not moving at all? But turning their velocity to 0 still causes them to be moved? 

 

I'll try some other things over the weekend. For the exploding in the video, have you tried more substeps?

[tious13]

No I haven't tried more substeps, applying your setup does increase the sim time consequently on my machine. Would it be possible to take the position and freeze it insted of freezing the velocities ?

 

here is my last flipbook, because I don't know how to delete particles in DOP and to reduce the draging effect I only melt the outer edge and hope to be able to remove the remaining part with a vdb combine.

flip_003.mov

Edited December 5, 2015 by tious13

[tious13]

Hmm so from your original image, you want the blue particles to be moving but the black ones to be frozen and not moving at all?

exactly !

you can see here that the particles with 0 velocity are getting pushed by the other ones, I may not understand correctly how to zero the velocities though.

[alksndr]

No I haven't tried more substeps, applying your setup does increase the sim time consequently on my machine. Would it be possible to take the position and freeze it insted of freezing the velocities ?

 

here is my last flipbook, because I don't know how to delete particles in DOP and to reduce the draging effect I only melt the outer edge and hope to be able to remove the remaining part with a vdb combine.

 

It should be possible, just need to save P into a new attribute as soon as the point enters the group so we havelike a final position and then have P = to that attribute/position the rest of the way. The outer edge looks like a cool solution , is SDF difference not working? You could probably even just give your sim particles a color and then attr transfer them to that original geo and delete whats not colored. With a high enough resolution it should be really seamless. Cant think of any reason either wouldnt work atm.

 

These are both so hacky though, Ive never had flip sims explode i wonder if johnny knows whatsup with that i mean the bullet video looks perfect and exactly what youre trying to do.

[tious13]

I understand the way you describe but have no idea how to proceed for saving P then reapplying it. I'm gonna try the delete group method as soon as possible

[alksndr]

I understand the way you describe but have no idea how to proceed for saving P then reapplying it. I'm gonna try the delete group method as soon as possible

 

Nothing I was trying was working ! But my friend anthony helped me out. Saves the attribute when it enters the group so yeah, just make your group based off temperature. It needs a lot of substeps for really good accuracy on fast moving points.

 

So If you just set a @hitpos = @P then itll overrwrite that position.. but if you do an IF hitpos == 0 (which it always is, since youre creating it) it will always stay at 0 until the first frame it hits the group and it stores it. Honestly not sure why that works, the way I was trying to figure it out was looking in the pop collision behavior cuz there is a hit pos there. It has the same kind of if thing, but yeah, kind of confusing.

 

 

 

BTW I would have just done it in your file but it seems like impossibly slow and moving the particle sep higher breaks it, maybe its cuz im still on H14.

 

 

EDIT: Nvm it makes perfect sense. Just realized why it works: the condition is always true at first, but because its not in the group it does nothing. As soon as it enters the group, it changes the number, and then next frame it does nothing because the condition isnt true anymore. Hope one of these ways actually helps lol

saveattrgroup.hip

Edited December 6, 2015 by alksndr

[tious13]

Thanks ! sorry I did not have the time to get back on this, I'll as soon as I can