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View Full Version : How to create these sort of cartoon clouds?


FluidEdge
06-17-2009, 10:50 AM
http://www.cgexplorer.com/_sys/wp/wp-content/uploads/partly-cloudy-pixar-3d-animated-short-film-575x322.jpg

Anyone know how these were created?

It's obviously not particles/fluids but rather polygon mesh with a cloud shader. How would you create this kind of shader in maya (mental ray)?

advice appreciated!!

FluidEdge
06-18-2009, 06:59 PM
anyone know?

Cheesestraws
06-18-2009, 07:04 PM
Have you tried using SSS with a gentle displacement map?

klingspor
06-18-2009, 07:05 PM
anyone know?Is this from the latest Pixar short?

My guess is the lower part of the cloud is just some sort of volumetric shader like you could achieve with Maya's fluids.

As for the cloud-character... Maya's ramp shader with some subtle displacement might do the trick. You'd probably want to map a 3D noise function in the surface transparency falloff to get that soft, fluffy look at the edges.

It's hard to tell without seeing an animation.

klingspor
06-18-2009, 07:36 PM
Here's what I've come up with in five minutes in the HyperShade based on what I described in my last post.

Just a sphere and one directional light. A lot of what makes that character look good is in the lighting, so don't expect a simple shaderball to look anything close.

With a little rim lighting it might by worth a try.

FluidEdge
06-18-2009, 08:00 PM
Thats a great help guys!

I'll have a play with these ideas later. Cheers.

swag
06-18-2009, 08:35 PM
i saw the making of from Peter Sohn last week @annecy the cloud char is 100% particle
they use a poly char for animation and filled the char with particles

FluidEdge
06-18-2009, 10:09 PM
do you know i was just googleing around and found there was a huge making of presentation for Partly Cloudy and Up at Annecy. I very nearly went this year too!!

(Did you do to the making of Up too?? We also need to make forests just like they have in Up - how did they model, shade and light those forests ;) )

I'm not joking but about 5 mins before i saw your post i thought about using the nParticle "fill volume" thing to do this!

This could be the answer to my problem. nParticles "thick cloud" looks great but we need to be able to animate and deform the cloud so enclosing them in a polygon mesh that we just turn visibility off sounds great.

smaragden
06-18-2009, 10:45 PM
At the Up seminar they mostly talked about story development.
Not much tech talk there. But it was good though.

FluidEdge
06-19-2009, 01:59 PM
Ok

i'm making clouds using the nParticles to fill a cloud polygon shape. However rendering is, well..., slow.

http://img8.imageshack.us/img8/990/nparticlecloud1jr.jpg

http://img10.imageshack.us/img10/7439/ncloudrender2.jpg

Even using just 100 particles on low quality settings is taking too long and as for 500 particles - well i've got a feeling 75 mins at crap quality is probably too long.

Does anyone know why nParticles take so long to render (granted i have ray tracing on and a few lights kicking about but 75 mins for 500 particles!!??! - LOL WTF ZOMG BBQ!!)

I've got a feeling i'm doing something quite basic wrong and thats why it's taking so long. Autodesk have helpfully not provided much info on shading and rendering nParticles (but their simulation tutorials are ok) can anyone point me in the right direction?

There appears to be some kind of banding on the second image that looks like it's coming from the fluid shader (voxels etc) - is the fluid shader what's slowing down the render so much? Do i need to optimise the fluid1 node.

It's very a unintuitve shading system Autodesk have made for their nParticles. Sure the simulations are nice but whats the point if you can't shade and render the bloody things!!

I'm getting closer to that original pixar image but to render at production quality and HD size is going to be upwards of 1 day/frame. :(

Cheesestraws
06-19-2009, 02:22 PM
The more cloud shaded particles overlap the slower the rendering will be, perhaps instead of filling an object you can emit from the object then goal the particles to their emission point. There is nothing special with what they have done with nParticle shading, they just use the old methods people had been using to shade particles before Maya 2009. Try reducing the shading quality on the on the fluidshape node, or perhaps instead of using the thick smoke preset use the other smoke preset when creating the particles which might render quicker.

FluidEdge
06-19-2009, 02:42 PM
hmmm

it seems turning off "real lights" in the fluid node brings the render time down from 75 mins to 7.2 seconds. :buttrock: :banghead:

unfortunately it ends up looking like this:

http://img265.imageshack.us/img265/750/quickncloud.jpg

flat and gray.

So i have either a nice looking cloud with 11 lights with ray tracing shadows (1 key, 5 fill, 5 bounce) or 1 "fake" light that renders really quickly.

I might have to loose the bounced light and shadows. and just go with maybe 3 fill lights?

jipe
06-19-2009, 02:48 PM
What happens if you use "real lights" but switch your shadows to depth maps with low res/high filter size? Just curious how much the raytraced shadows are contributing to the high render time...

FluidEdge
06-19-2009, 03:10 PM
It's quicker (~3-5 minutes) but doesn't have anything like the depth of the raytraced version.

I'm wondering if BSP acceleration would come into play here?

I'm also wondering about an IBL/HDRI setup with final gather rather than using ray traced directionals?

Sorath
06-19-2009, 05:28 PM
could it be somehow possible to render out normals for such particle clouds? maybe it's worth a try to relight in comp with some occlusion, env occlusion and normals.

noizFACTORY
06-19-2009, 06:56 PM
I haven't seen the short film yet but does the cloud character keep changing its shape during the course of its movie, with puffs of cloud separating from the main body and all that as the character deforms or is it mostly just stuck to the character and deforming like regular skin?

I'm just trying to understand if the fill with particles method is even useful in such a scenario.

-Sachin

FluidEdge
06-20-2009, 12:26 PM
Well i'm upto 4 1/2 hours a frame now!!

But it looks just perfect. Exactly the look i was going for. However 4.5 hours isn't going to fly so i'm going to have to look at other methods.

Depth map shadows just don't give anything like enough "depth" to the shadows ironically.

I'm going to look into using 3delight and deep shadows next.

I don't really want to go down the route of lighting in post with vectors etc if i can help it as we're on a tight schedule and could do without the extra time that takes to comp and get that right.

Sybexmed
06-30-2009, 09:38 AM
If you can post the scene your working on maybe someone can help ya.

FluidEdge
06-30-2009, 03:06 PM
i'm down to about 2mins now!

its all about getting the lighting and shadows right.

i'm going to write it all up into a blog post soon.

redforty
06-30-2009, 08:54 PM
Awesome! Would you be able to post a wip render? I can't wait to read what you've learned.

Sybexmed
07-01-2009, 12:59 AM
i'm down to about 2mins now!

its all about getting the lighting and shadows right.

i'm going to write it all up into a blog post soon.

Be sure to post a link on here, i want to check it out.

leif3d
07-01-2009, 03:55 AM
Pixar wrote a Volume Shading system called Atmos (Raymarcher) and rendered it with RPS 14.

I'm sure you can achieve a similar effect in MR.

FluidEdge
07-01-2009, 08:44 PM
will do!

I've got something that looks quite close to the Pixar screenshot I posted but haven't got the render with me here.

They're clever chaps over at pixar aren't they. I did looking into raymarching in Mental Ray but quickly abandoned the idea. I'd like to see the white paper on that Atmos system though!

JohnPetrucci
07-29-2009, 08:57 PM
so did it work?? Im very curious about this!

Leionaaad
07-29-2009, 09:49 PM
how about doing it with fluids/particles, then blur it in post?

Sybexmed
07-30-2009, 07:55 AM
Im also curious of a workflow to produce this effect? Anyone?

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