VOP's

Joined: 13 Jan 2007 Posts: 5

Hi All

I would really like to learn more about all areas of VOP's, I can see the potential and power it offers. Is there any tutorials out there? I can't find much info about it.

Are you guys at CMIVFX planning to create a tutorial DVD on VOP's. I've just purchased the L-Systems DVD and am learning heaps, a VOP's
DVD would be awesome.

Also does anybody know how to create a simple ramp in VOP's like the one in COP's? Please Help

Thanks
NIck Sullivan, Sydney

Site Admin Joined: 14 Nov 2006 Posts: 247

VOP's of course we are. We wont quit until everyone is a houdini expert. Wink

stand by for more by david.

Joined: 13 Jan 2007 Posts: 5

Unreal! I can't wait, any idea when it might become avaliable?
The L-Systems DVD is awesome, I didn't realise the power that the L-System SOP offered.
My thoughts exactly everyone should learn Houdini, It's not that scary!

Thanks again
Nick Sullivan, Sydney

Joined: 15 Nov 2006 Posts: 29

About the L-systems DVD. Thanks very much!
And remember this is only the first of 4 DVDs devoted to L-systems.
In the following: you will learn how to animate a tree ( with DOPs, reacting to wind of course, but also using branches as tentacles), how to create realistic fully contollable crack patterns , how to grow and paint plants on any surface, with much more options than Maya PaintFX ,how to create more elaborate tree geomtry and corals, how to shade and render them how to create a city pattern growing ( with some extended fully-scriptable l-systems) and more (Lsystems in Lsytems, snowflakes, recursive modeling at the very end...).

About VOPS. ( after l-systems.. sorry).

Sure we will release DVD(s) about VOPs! DVDs released for now assume that the user has already a basic expertise with VEX. But there is a HUGE AMOUNT of things to say and to do with VOPs.
Vops can achieve some very different tasks.

In shading contexts it is nothing less than a shading language which is as powerful and often more than renderman RSL ( more options, such as all the raytracing features that were here before renderman, the Point Clouds, the i3d prior to raymarching...).
When we teach VOPs in rendering, we will actually teach rendering from A to Z ( Z being what a real TD must know!)

In SOP context, it is nothing less than a tool to create any kind of deformation that you want, it's an entire field.
One of the limitations though is that it works on points, and you may want to make it work on primitives. It is possible with one or two simple tricks as long the operation you want to do with primitives is possible.. ( primitives are dependent upon points).

In particle context, they replace all the tedious expressions and open Houdini to the immense field of behavioural animation.

Of course CHOP context is an "abstract" context because channels can be anything you want.

COP context is similar to surface shading context in shading context: it allows to create any procedurally generated texture that you want, but since it can work with multiple inputs, it can create all the scripted compositing filters that you want and that you usually use in Shake/Nuke/Fusion, any transition that you want by animating the parameters.

Yep, Vops are incredibly powerful. they are a visual programming environment for VEX: which means if you know how to read a VOP network as a replacement for code, you don't make syntax errors ( no debugging!) How great is that?!!

All this topics will be covered in the further DVDs with a special mention for shader writing and rendering

About a Vex Ramp you can use the Ramps VOP. It depends on how is you ramp ( vertical/radial)...
Cheers.
David

FEEL FREE TO LIST ANY PARTICULAR TOPIC YOU WOULD WANT TO BE COVERED, SPECIAL QUESTIONS TO HELP US MAKE DVDs EVEN CLOSER TO YOUR NEEDS. THIS INFO IS REALLY PRECIOUS TO US!

Joined: 13 Jan 2007 Posts: 5

What a reply!! I can't wait for the other L-System DVD's, They sound great. Also the much anticipated VOPS DVD's, I'll have a think about the topics I'd like covered.

Is it going to be possible to recieve a cheaper price if buying all of the DVD's on a particular topic.

Cheers
Nick Sullivan, Sydney

Joined: 21 Nov 2006 Posts: 63

Well the fusion dvd pack comes out cheaper then buying all the dvds individually. So probably, but that's to the discretion of cmivfx, although Chris rarely forgets a customer.

But back to vops:

David, you mentioned point clouds and I3D. If you don't mind, you must be busy as hell, could you maybe answer these questions:

1- Point clouds.....what are they? How do they affect/interact with my 3D applications (Cinema 4D / Apprentice version of Houdini). Do I need them?

2- On the sidefx forums, there has been some talk about afterburn (raymarching) versus I3D. Many say results are similar, except I3D requires much more work to achieve AB results. Can you shed some light on it?

3- Please Please Please tell me there will be discussion on how to create a good I3D shader on an upcoming dvd... The reason I say this is because when ever I create something using I3D, it sucks. Granted I'm horrible at houdini and I'm still learning the basics of what's under the hood, alot of people on the forum (sidefx once again) say that Houdini 9 should ship out with a better I3D shader and such. Any info on this?

Merci beaucoup... et la France ne gagnera jamais la coupe du monde. Vive l'Italie. (sorry, had to kick in some french once I learned David was from France)

Joined: 15 Nov 2006 Posts: 29

Hi Steve! Very busy indeed..

1. Point clouds are just... sets of points with some attributes associated stored in a good way for lookup/access. They're used to fake GI ( to instance multiple lights) but also to fake SSS ( the trick is a little bit more complicated)...

2. Well, yes. A i3d is a three dimensional texture which is not procedural...
So this is something very very heavy ( to have equivalent quality as 2d 2000*2000 texture you will need to have 2000 ! textures for the third dimension), both at CREATION ( the file is big) and when it's used in shaders: render times are very long.
It actually stores a unique value which is the density and which is "integrated" along a ray .
We will teach it because if we teach rendering, we will teach everything. But clearly having a good understanding on how raymarching works ( which is not that difficult when you've already put your hands into shaders) is much much better and much much quicker since you will then compute the density procedurally which doesn't use any texture ( much lighter and faster ), and which is much more precise.

3- I have no special info about this. i3d is inherently something very big to handle: SESI can make them better with faster texture access, but i think that's the maximum they can do.

So, you know some french, Smile

then i will answer:
Je considère que nous n'avons pas véritablement perdu la coupe du monde , je trouve que nous étions vraiment meilleurs et plus solides. Et sans l'exclusion de Zidane, nous aurions bien évidemment gagné. About next world cups... that's another story! Smile

Joined: 21 Nov 2006 Posts: 63

That's just what I needed to hear. Thanks alot David, but to continue this just a little bit more (just a little bit, I promise haha):

If I3D is heavy and long on the pc, why is it used? Why not just bother adapt some form of raymarcher for Houdini (and is this possible by the way?)?

Ne commence surtout pas a propos de Zidane Exclamation

Joined: 21 Jan 2007 Posts: 4

Hi David

Just wanted to chime in as someone else who's very keen to see more material for vops. No preferences per se... just all of it really Very Happy

. After vops, my next weakest area is in chops (if you're looking for a direction to go in...).

Hopefully if sesi can nail the new workflow changes announced for H9, more non-houdini types may give it a shot. Having lots of video training for them to lap-up might prove to be the deciding factor.

Oh and great work on the l-sys dvd - cant wait for the next one!

Smile

Joined: 15 Nov 2006 Posts: 29

Hi, Steve ( the answer to Moose follows in page 2)

About i3d.
Several explanations about how it's still used ( these explanations are mine, i don't say they're the exact ones)
First thing is that i3d can also be used in modeling with the IsoSurface SOP ( which creates implicit surfaces). It's much more interesting in this context because it doesn't require the same amount of detail. I guess SESI wanted to have a unified 3dimensional-array-of-data file format.
Why is it also kept in rendering? Maybe it's beacuse people are afraid of writing a "ray marching" piece of code.
About raymarching. I should say ray marching ( in two words). I didn't explain what it is. It just consists in iterating a loop along a ray ( this has not to be implemented in Houdini, it's just the name of a technique and it was already used in Renderman when it didn't support raytracing). What is implemented in Houdini is integrate3d which performs ray marching through a texture. But you can implement it creating a virtual
ray ( just a point and a direction).

Ton français est bon.. But, to be honest, i'm not a big football fan, so we won't go long on this topic Smile