Snow with falloff?

[bcbarnes]

Looking at the pictures, my first thought was that something like DirtyNUTS could probably do it, although I haven't tried it.

[AdamT]

Shouldn't be too difficult. Just use a snow material with BT Falloff. Guess you'd have to do it for each material though, which would be time consuming and require a lot of trial and error to match the scale between parts.

[Peoples]

Yea - I did some tries with it but there's no easy way - you have to assign the snow to each part separately - if I just group the whole sled together and put the snow with falloff in the alpha to it nothing happens. And if I put it in each part - f.ex the body under the windshield also gets snowy which would not happen real life..........well - hava to keep tryin..

[flingster]

yeah bit of a problem really...i was trying to get the same effect on a xmas tree....the only was i could come up with was selection of area required....never went back to it though....did you come up with anything?

[JoelOtron]

I suppose this is one solution, I created my snow texture then used SLA falloff in my alpha channel. You could use fresnel or gradient as well. I took that into distorter to make the alpha more irreggularthen applied theee texture to the grouped object (sphere and pipe) which were already textured separately. Selected copy texture to children and this is what I got. Im sure with more tweaking you can come to a better solution.

[Peoples]

Well - I gave up quite fast, I didn't find an easy way to do it, the model is way too complex for some simple falloff (please prove me wrong...:rolleyes: ).. It's very hard to control the parts that wouldn't actually get exposed to the snow - and I didn't get the texture to work at all even if I assigned it to the group and copied the texture tag to children....So - I'm all out of ideas............:D

[Claudio72]

aaaaaaaaaaaaaaaaaahhhhhhhhhhhh
DON'T GIVE UP!!
Take this file and study the Nukei, if you can invest some hours in studiing that shader you should come up to something real fast!!

I've put 2 quick and dirty nukey(10 min experiment but I know quite well how nukei works) and a standard shader(farina) that use noise in luminance and gradient in color channel.

hint: enable and disable the secondary surface to see how to use it on another model, the second surface is just the original crumpled.






http://www.crosio.ch/images/snow.jpg
1.4MB to download (http://www.crosio.ch/images/snow.zip)

[sfshook]

You might want to look at this tutorial. www.creativecow.net/articles/libisch_dan/moonlight_mountain/index.html (http://)

[Per-Anders]

ok, well here's a preset i knocked up quickly that you might like

http://www.peranders.com/c4d8/samples/jpg/snowfalloff.jpg

and the scene file is here

http://www.peranders.com/c4d8/samples/c4d/snow.zip

this file is tiny by the way... 27k

[Per-Anders]

and as for a quick explanation of my shader. the alpha channel controls where teh snow is. but there is also some displacement (looks good with hypernurbs or highly subdivided shapes, the fusions alpha in displacement should really be set to tjust a copy of the fusion in the alpha channel, so you don't get bumps where teh snow isn't, you can also just switch this off). slight luminance to colour and light the snow, then bump with turbulent noise as out of all the noises i find this and fbm give the best "powder" like effects.

the alpha consists of a noise in teh top channel that defines the breakup of the snow, overlayed using LEVR on a bhodinut falloff. the falloff simply controls the angles where teh snow appears on any model. using levr causes it to break up accross the gradient by the noise shape, which is rather nice. i then back off the blending a little as this causes levr to "soften" as i didn't want too harsh an edge, if you play around with teh falloff, the noise and the ammount of levr you can get different effects, harder snow, more or less snow etc. there's an explanation of levr in the new manual and also in the cel shading tute on my site that might help here.

in the example you gave there was a litle undulation and uneven distribution of teh snow over teh windows, to get this effect you would probaly make the noise smaller and soften the levr by making the blending slightly less strong.

anyhow i hope this givesyo uenough to get going and get some snow on your snowmobile :)

[BoERS]

Here is my 2¢:

You will need to render this out in 3 passes.

1) A normal beauty pass, no snow.

2) A snow pass, with the snow made however you want. It doesn't even need to use the 'falloff' shader or anything similar. Coat the whole snowmobile in snow. I think to save time you can make the objects invisible directly, but still visible to the GI.

3) Remove all of the lights from the scene. Duplicate the snow texture and replace it's colour channel with a pure white. Make sure to remove any transparency, alpha, luminence, and specularity. Apply this new texture to every object. Now create a distant light shining down on the snowmobile using 'Soft' shadows. Ramp the parallel width of the light WAY up... I'd say around 8 to 10 times the length of your model.

In photoshop, or something comparable... beauty pass on the bottom, snow pass on top, using the light/shadow pass as a mask. You can adjust the curves of the light/shadow pass to adjust the snow's perpindicular tolerance, as the mask will be pure white where the surface is completely perpindicular to the light, and will ramp down to black as the surface becomes parallel to the light. I would sugest making everything above 35% to 45% grey, pure white.

This should allow the snow to be configured however you want, but only allow it to fall on the very top polygon, even if there are several objects in verticle alignment. ie) The light should cast onto the windshield but not onto the body directly below it. This will effectively mask out the part of the snow pass that is directly below the windshield.

And due to the procedure taken, there are no scale issues with the falloff as with some of the other methods previously mentioned.

Take a look at my (very) simple example.

Hope this helps! :beer: Use it wisely...

[chris_b]

... here's an example of a BN falloff based snow shader applied to a more complex model with many parts and totally screwed up texture co-ordinates.

I found that by applying spherical mapping to the various parts and then scaling the projections to encompass them (using the Texture Axis Tool), i was able to get decent results quickly. You could also use selection sets to force exlude areas that you wan't to keep free of snow, but it seems that falloff (with the appropriate alpha) generally puts the snow in all the right places.


http://www3.sympatico.ca/kdagg/screen_01.gif

http://www3.sympatico.ca/kdagg/SNOW_tst00.jpg

c

[Peoples]

Well - here's a quick try with sector996's tip - the lightning is waaayyy too exposed but I think I'm getting closer......Thanks alot also mdme_sadie for your input - I learned alot from your preset. The separate passes are actually the most realistic way as where te snow would fall in real life, with falloff it's very difficult to control it when dealing with such a complex model as this.

But thanks again guys for your excellent tips - I'll keep finetuning this and will show you the results..

:wavey:

[Claudio72]

I like the result you got and I can't wait to see the final version.
Pay attention to the horizon because it ruin a bit the photorealism.




x mdme_: I've used quite the same technique in the fusion channel (this make me HAPPY) in my NUKEI.

[H. Ikeda]

Cool stuff, very nice work and suggestions! Those are beautiful and convincing.

Just would like only some touch of thickness...it reminds me of a snowfall simulator proposed in Siggraph before (maybe a few years ago).

Below is a simple experiment with TP (no particle-particle collision) and Pyro. Just a trial.:)

Cheers,

[Per-Anders]

nice image... though you must have the rendering patience of a saint! this is the first time i've seen anyone post anything done with pyrocluster (wouldn't have thought it possible ;) j/k).

[H. Ikeda]

:):):) In most cases it could be. But in this case, low Volume (40%) and low Density (5) may be enough for snowfall, so the rendering time was rather reasonable, which I also didn't expect.:) No need for age effects, but full shadow settings for a touch of thickness. Rather than that, TP was heavy with particle-particle collisions. This may generate the deep snow, though.:rolleyes:

c4d file(21k): snowfall.zip (http://www.interq.or.jp/aquarius/ikeda3dr/data/cgtalk/snowfall.zip)

[Peoples]

A small update - re-rendered the snow-pass with a bit subtle lightning - I'm pretty satisfied with this one. It's getting to look like it was left in the snow and forgoten there.....:wip:

[Gunter]

looks really pretty, very realistic. I suppose - hard to see - there is snow on the parts below the seat too?
Very great, interesting thread.

[Claudio72]

Peoples, you need some more lighting in this last image you post, but the snow looks like really good. It's more realistic than the frozen effect in the calibra lw image.

[bjotto]

If you combine the fallof with dirtynuts you can remoce the snow from parts that the snow shouldn't reach

[AdamT]

Looks great! Now you just need to pile up some snow on the runners. A little Proximal in the ground's displacement channel can do wonders for this effect.

[Anadin]

This is getting better and better - the proximal ida is cool!

Thanks for the snow file Hiroshi - I need to do some catching up!

[mickymouse]

Thanks for the shader... it's no Terragen, but I'm happy with it. Maybe if I mess with it some more, I might get it closer.

[kiwi]

Looking really good :thumbsup:



If you want it to look abandoned dont forget to build up snow underneath it as well,and actually cover most of the mechanical parts that are underneath.



Stu.

[medula]

Ok, I've been enjoying this too much! Here's 6 presets for you to have some fun with! :lightbulb

Version 8 file .sit: click here for the 6-pack (http://www.rit.edu/~mwcfaa/medula_snow.c4d.hqx)

Enjoy!

[Peoples]

AdamT - could you give me any hints on that proximal stuff on the grounds displacement channel? I tried some experiments but didn't see any results....:rolleyes:

[JoelOtron]

1. Make sure your ground plane has a relatively high subdivision (a ground plane object wont work as well)

2. Make a copy of your snow material that will only be applied to the ground--not the snowmobile.

3. In your displacement channel for the ground snow material, choose the snowmobile (or the ski objects) as the proximal object. see my settings below--but you can tweak and tweak to our hearts content.

[JoelOtron]

Here are the settings:
(server was not letting me upload the image here)

http://www.joeldubin.net/uploads/test/prox_settings1.jpg

[Peoples]

mmpph....thanx for the tips - I still cant see any results - I tried the same settings and a simple scene with a figure. My plane was the default with 20 subdivs....Does it matter how deep in the plane the guy is..??

[JoelOtron]

The object with the prox material needs to be a poly object.
The bottom of the skeis only need to be in contact with the ground for this to work.

[JoelOtron]

Also--the higher the subdivision of the plane, the smoother and more precise your results will be.

[Peoples]

So a basic plane object won't work...? I have a "ground" made from a plane primitive - but I dont see any effect......Do I have to make it editable? Does the texture mapping have some affect? I'm still testing with this figure scene I made up similar to yours JoelD

[JoelOtron]

So a basic plane object won't work...? I have a "ground" made from a plane primitive - but I dont see any effect......Do I have to make it editable? Does the texture mapping have some affect? I'm still testing with this figure scene I made up similar to yours JoelD

yes--you need to make the ground object editable (which converts the primitive to polygons). That should do it. Basic default UV mapping should work. You may also have to convert the skis to polys to work--I never remember which method works--especially when I havent had my coffee yet. I can upload the file if you want it.

[doohicky]

:buttrock:
Thanks for all the presets guys....

[JoelOtron]

Heres the zipped file for what its worth.
The environment map is not included--but not neccesary


http://www.joeldubin.net/uploads/test/prox.c4d.zip

[Peoples]

Thanks alot JoelD for your patience - my problem was that I made the ground editable but not the Figure...........So now it works and it´s time to try this with the snowmobile..:wavey:

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.