visualising a volumetric image sequence in vray

[super gnu]

playing around with a fractal generator.. one export option is to render out b/w slices through the fractal at a given step size.

i can use Fiji to create an obj from the image sequence, but for any level of detail the mesh size becomes outrageous, and 32 gb of ram is a real limit to mesh detail.

is it possible to somehow render this data directly in vray? i could of course painstakingly opacity map 2500 images onto planes stacked in teh viewport, but i cannot imagine what would happen to rendertimes with 2500 transparency levels, plus the shading would be screwy. not to mention it would take ages.


it would be nice to plug the image stack into vray fog or ideally a volumetric shader, or isosurface generator, but unless vray3 has something in this regard vrayenv fog is the only option.


any suggestions?

[joconnell]

Depends on how the file data comes out, something like krakatoa's prt, fume's fxd or the sony libraries used in houdini would be a better fit. Vray has no direct volume rendering functionality as such. The transparency level thing is a complex enough thing to sort and normally done by a raymarcher (which literally fires a ray through a volume and you tell it how many steps to take along the way - kind of similar to your 2500 images with each being a step) which will cut off once the thickness of the volume builds up to a certain opacity.

[super gnu]

given that the fractal is essentially a solid object and the images are 2 bit b/w on/off affairs, id imagine an isosurface would be a good option... vrayiso... where are you?!?

just to note, im currently trying to generate a mesh using fiji.. 2500 images of 2500x2500, and its been running for 1 hr... ram usage is currently at 29.7 gb and rising... also if i understand correctly fiji is estimating a 14gb mesh file. bah. will also have nowhere near the detail i was hoping to achieve... what would be nice is something like mandelbulb 3d but built into max with a basic viewport representation, and of course, vray compatibility.

[joconnell]

Sure, ideally you'd have an object in max that solves the equation and you could direct raytrace that. Frost would also be a really good option since you can load particle caches and mesh those but again it all depends on Fiji making a file that you can use. Even if you can get it to save out a simple csv text file for the voxel array, then you'd have something you could work with. Plain text is really handy for this stuff!

[super gnu]

would be one hell of a text file.. my obj is 3.9 gb and still growing.. yikes.

[super gnu]

ok so thats a dead end.. obj file was 6.5 gb, and my ram hit the cieling when importing to max.. 485 million polys, and it -unsurprisingly-fell over.

[joconnell]

Sure - you'd have to get the program to write to vrmesh directly like naiad did to have a fighting chance. A mesh though isn't going to be able to keep proper volumetric detail for all the inner details of the surface if there's any subtlety to the opacity levels in each "cell" of it. Back to the drawing board

[super gnu]

is there a particular architectural reason why vray has never had a proper volumetric material? seems like an obvious and powerful addition, and one that has been present in various other renderers for ages..

[joconnell]

I'd say it's just that it's not hugely useful in archviz for one thing. The environment fog serves a certain amount of this purpose too. I could be wrong but I think it's on the development list for vray 3. For this specific case though you're talking about a proper full raymarcher rather than just a volumetric shader and likewise the second issue of actually getting the data in. It'd need something like a smaller afterburn or fume inside of vray.

Really it's krakatoa for this type of stuff.

[super gnu]

i thought krakatoa was just a "render squillions of particles as points" kinda thing..? can it do volumetric solids with gi etc?

[joconnell]

It can do light scattering alright and also renders voxels which is like a big cube made up of many smaller cubes and each of these contain a value for transparency - its as if your cloud is made up of pixels of opacity. They've also got a really good file format for saving millions of tiny things whether particles or voxels.

[t1t4]

Sounds like you should be looking to convert the image stack to a point file rather than geometry. Once you have the data as points you can probably use pflow to easily convert the points to geometry based on their color or other property depending on what data you save to the points when you convert the images to points. Once you have the data as points it should be much easier to manipulate in 3d apps like 3ds max. I think it would also be easy to render with phoenix or any other system that can render geometry based on particles.

Of course I have not done this in 3ds max so I don't really know what the work flow is but it seems like it should not be to hard to covert a stack of images to a point or voxel file that you could easily read into max.

[henning]

I'm also for more volumetric things in V-Ray but for now you might have the more luck with Houdini and its new OpenVDB features which are really fast at meshing.
The free version even can save obj files

[Raven]

I have also been looking into this
Not sure if you have tried this workflow
http://mourelask.weebly.com/3d-fractal-creation.html

Also found this
http://www.fractalforums.com/mandelb...nverse-method/
Wish I could get that VRay shader from Lechoo, but cant find anything more on it.

Also see that Master Bercon has coded them before aswell
http://www.ylilammi.com/2013/09/field-trip/