methods to render volume

[MENOZ]

hello.

i'm trying to understand how to render volumes in houdini.

i found that there are 2 methods.

one is to take an object and append a iso volume offset SOP. then use a shader on it, like billowy_smoke

the other is to use i3d file. export my i3d file or sequence, and than read it back, and again apply a shader on it.

if i don't write on disk the i3d files, houdini use something similar to render my volemetric effect?

wich solution is better? is one faster than the other? i guess that with i3d i can make a sort of cache of my effect, writing i3d image on disk.

it's correct?

thank you

[MENOZ]

do i missed something?

[Jason]

do i missed something?

You can also save to and render from .bgeo files if you like, using the Mantra: Delayed Load procedural - which is similar to rendering .i3ds, except...

i3d's use less RAM to render and should be filtered better than rendering Volume primitives directly. The only issues are that you have to generate and maintain them - and there are a couple of subtleties to be aware of, such as you have ensure yourself that you are writing out your i3ds at the exact resolution you generated them at or you'll suffer a small quality loss. I think, though, if you are getting good results from i3d, it should ultimately be more efficient.

[MENOZ]

let me see if i understood.

i can: export my geometry to i3d file. and recall it with a isoSurface.

this give me the "same" result of

append a isoOffset to my geometry.

for "the same" i mean the same result when rendering. it's right?

[Tamis]

Mantra uses the same way of rendering volumes for both your descriped methods.

The advantege of one method over the other is that if you have a realy heavy volume object that is being calculated by a fluid solver you can first solve the simulation and write the volumes to disk.

then you can bring em in when you wan't to render them, this saves you from having to recalculate the fluid solver for everytime you want to render.

[MENOZ]

thank you!