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Erosion Effects

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Wondering about these effects

I have a project coming that might need a vairant of this type of effect.

What is the basic workflow for this?

Is this an animated displacement map?

Is it shape animation on the Geo or possibly both?

Is it (dare I say it .... an animated

boolean)? This sounds dangerous.

Any info would be helpful.

Thanks

Lyn Caudle

VFX Supervisor

Janimation

www.janimation.com

lyn@janimation

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Other people here probably know more but from what I recall hearing was that the eroding landscape in the Time Machine was done in VoxelBitch (aka VoxelB aka Storm). So voxels. I wonder how much you can do with .i3d and an IsoSurface SOP with animated density.

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Oohh I like that.

Sounds promising.

I'll keep looking about.

Hopefully someone that worked on these shots will

reply.

Thanks much

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What Edward is talking about is a hero stone arch that got eroded away. At that stage there where not very good tools in Houdini for doing it and the best way we could do it was to voxelize our inital arch geometry and then erode that voxel data down and extract an iso-surface from it frame for frame. The same thing could be done with i3d now quite easily - and hopefully in the future we'll be able to use Volumes (Level Sets) to do it too. Anyhow, the resultant geometry was rendered with an additional animated displacement shader for added detail (by Darren Hendler).

The distant canyons were rendered with Mantra (v4) using animated displacement mapping and incorporating some fancy "bouldering" algorithm (basically samples were projected to Voronoi boundaries to look like rocks; something devised by Johnny Gibson here - there is a SIGGRAPH sketch about it somewhere).

Terragen was only used to conceptualize the terrains in the lookdev stage on Time Machine. However Terragen was used for a Kaufman movie shortly after Time Machine called "Adaptation" for a similar erosion effect and has been responsible for our terrains ever since.

Hope this helps.

Jason

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What about using the new IsoOffset SOP?

24119[/snapback]

For simple erosion this might be ok, yep. When we did ours we wanted some unevenness in the erosion pattern (some types of noise) and to introduce holes through the sheet of rock in a directable way we found we needed to use a voxel set because it is hard to punch holes in geometry like this . We could easily subtract noisy spheres from the voxel buffer with VoxelBitch to cut a hole through, and even mix in a target voxellized shape where we wanted to- and the isosurface behaved surprisingly well.

We wanted to be able to erode the upward facing surface different to the side-facing surfaces and wished for a shading context to do this easily. With i3d you could use the gradient of the volume to determine a "normal" and apply such an effect now quite easily.

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The thing with using .i3d is the resolution requirement though.

24123[/snapback]

Very true - although you can get away with fairly low resolutions if you add detail to the geometry with a displacement shader. I suppose 256x256x256 would be ok for a rock like the one we used in Time Machine. I haven't used i3dgen in some time and I can't remember how slow it is or how big the files get. VoxelBitch can work at resolutions above 1024x1024x1024 without an issue and I don't know if those resolutions are reasonable in i3d.

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Thanks Guys

This is helpful. I'll try the Iso offset,

as well as i3D- Iso Surface solution.

I think the speed and resolution with i3D will become a factor.

The largest I have ever been able to tolerate is 512x512x512,

not that it won't do more, I just havn't needed it...yet.

Thanks

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Yeah, it all really depends on how much erosion you plan to see, and at what range.

A canyon/valley scene kilometers away might be a VEX Sop and shader solution. A nearby hero rock, the isosurface solution.

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You could also do it with raymarching through your geo directly .

Here is a little example :

RockTest.mov

Sven

24144[/snapback]

Ahh very nice Sven

Thats very close to what I will want to do.

What is your workflow for this?

Wouldnt it be cool to see the little leftover pices fall

after everything erodes from around it?

The effect I want to do would be faster for my particular use.

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I supposed I might be a little blind this morning and somehow didn't read it (in my skimming), but I am actually a bit curious as to what kind of custom VEX SOP they built to accomplish the effects.. Any one can shed some light? :)

Thanks!

-Alex

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The workflow is quite simple .

-Model your object

-Assign the Shader

-Setup the shader to your liking

-add an Iso point attribute

-animate the iso attribute the way you want your object to erode ( a iso value of 0 means your surface looks at that point like modeled an iso value of 1 means the object is not visible at all at that point.

post-535-1138297766_thumb.jpg

Sven

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Thanks Sven

Great! This is cool!

I think as this event will be quick I can add small

debris with DOPS which will help enhance it a bit.

Hey Alex I too would like to kmow more about this VEX SOP.

I will look into it and see what I can find. Might poke around in VEX for a bit as well. I dont have any experience with VEX to speak of

but I probably can't hurt myself.

Thanks

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The workflow is quite simple .

-Model your object

-Assign the Shader

-Setup the shader to your liking

-add an Iso point attribute

-animate the iso attribute the way you want your object to erode ( a iso value of 0 means your surface looks at that point like modeled an iso value  of 1 means the object is not visible at all at that point.

Sven

24155[/snapback]

?

This is very interesting, does all this magic happen in surface shader only?

Could you post vop network image?

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Maybe hightfields textures generated here could be used to add the erosion effects.

World Machine

Animate them using blending?

*Edit

Here is a try at it.

The only part that can count is the first second of the animation :unsure: If you scroll back and forth, you can even notice some dirt acumulation on the eroded parts

It is obvious that it needs more steps for the rest of the animation and im not even going to mention how bad I screwed the last mapping <_<

erode.mov

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?

This is very interesting, does all this magic happen in surface shader only?

Could you post vop network image?

24170[/snapback]

Yes all surface shader

post-535-1138351307_thumb.jpg

Sven

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