Jump to content

Subsurface Scattering Using Point Clouds


Recommended Posts

Here's a version of the shader, and a demo hip.

The sss functions support varying scattering attributes (like texture maps), but the shader doesn't make use of it as this info would need to get pre-baked into the point cloud itself (at the sop level) and it just complicates things for this demo.

There are lots of details in there, but instead of going into some long-winded explanation right now, I'll just put it out there and answer questions as they come ;)

The demo hip file produces the following image:

test1.jpg

... which in my system, renders in 2m59s (the more translucent the material, the longer it takes because it has to integrate over a larger volume... and the teapot is pretty translucent).

Again; lots to talk about, but I'll wait until people (Simon ;) ) have had a chance to look at the code; then we can chat.

Here's the bundle

Cheers!

@Marc: Again; I can't see a way to attach images.. is it not enabled in this forum?

Link to comment
Share on other sites

Wow, there's a lot of stuff in there Mario, most of it is over my head. I'm a hack master only, this is real live hard core math. Thanks for giving it away though :D , I think I can figure out enough to use it, even if I don't understand it.

Sure makes pretty pictures, I guess I can retire the old SS otl.

Out of curiousity were you working on this with Sesi before I posted that?

I have another mad idea for the point cloud functions, I bet even you can't guess what though..... :ph34r:

Link to comment
Share on other sites

Out of curiousity were you working on this with Sesi before I posted that?

13153[/snapback]

Nope. At that point I had an in-house solution that involved a *lot* of ray tracing, and was based on the ILM/Hery approach. It took much longer to render, naturally, but it gave me a chance to get cosy with the math... so that when I started working on this version, it was just a matter of learning the point-cloud tools and applying it. This version was written two weeks before the user group meeting, bouncing some stuff off Mark Elendt. (we found a nasty bug with shadows and point clouds in the process, which he fixed literally a couple of days before siggraph... Mark rocks! :) )

I have another mad idea for the point cloud functions, I bet even you can't guess what though.....  :ph34r:

13153[/snapback]

You got me this time. :lol:

Link to comment
Share on other sites

You got me this time.  :lol:

13156[/snapback]

Well i'm not sure if it will work yet, it's a bit off base. I was toying around with texture synthesis over arbitary manifolds, and not being able to use the hdk I hit a bit of a brick wall. Vex sops just couldn't handle the number of points required, but I wondering now if there is a way into this with point clouds directly rendering a solution into a texture map. It might not be possible, maybe hdk is the only way, but I'd like to see something like this in Houdini eventually. You ever done anything with texture synthesis :rolleyes:

Link to comment
Share on other sites

Hey Mario

You are correct, uploads were not enabled in this forum. They are now though... If you notice anymore then feel free to pm me and I'll change them.. Still busy working the kinks out here :)

Also, I'll put your bundle up in the codex.... er... shortly ;)

oh, and by the way : :notworthy:

Link to comment
Share on other sites

Well i'm not sure if it will work yet, it's a bit off base. I was toying around with texture synthesis over arbitary manifolds, and not being able to use the hdk I hit a bit of a brick wall.

You ever done anything with texture synthesis :rolleyes:

13163[/snapback]

I guess you're talking about the Mark Levoy paper (SIG,2001)? -- pretty cool stuff!

I can't say I've looked at it in any detail though. I'd have to read it before I can get a feel for whether point clouds would help in that case... maybe someone else here has tried it (Jens ?)... I'll have a look.

Cheers!

Link to comment
Share on other sites

It's my understanding that the "lifetime" for an unshaded point is the duration of the render. Thus, if the point is pcexported, then it's no longer unshaded for the rest of the render.

I don't know what happens in OP contexts though. If a point is unshaded in a SOP and we export a value to the point, when can we expect that point to be unshaded again? I would expect the next time we run the VEX code, but then again, I could be wrong.

If you render multiple images in a single IFD, I'm not sure what would happen either. Would you be required to re-shade each point for each image?

Link to comment
Share on other sites

Hey Andrew,

Yes; what Crunch said ;)

The lifetime, as per the docs, is "until the texture cache is flushed". In the case of the shading contexts, this can be safely taken to mean "until the frame is done rendering" (and multiple frames are multiple calculations, yes). And in the OP contexts, I would imagine you could take it to mean "until the end of the cooking"... at least that's how I read it, but I'm not 100% on that last one.

Hope that helps.

Link to comment
Share on other sites

Hey all,

I havent yet commented on this, but GREAT job, Mario! B) I may be using this type of this pretty soon, actually.

After speaking very briefly with Mark about pc-textures, he mentioned that the spec does include the potential to be able to write out the pc-textures to disk after calculation. This is more in line with traditional caching and should allow full caching of the resultant illumination (or whatever you're using these for).

Anyhow, we're all back from SIGGRAPH (at least mentally) and excited by the good stuff coming up!

Cheers,

Jason

Link to comment
Share on other sites

  • 1 month later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...