[Sidefx-houdini-list] units in houdini

Jeff Wagner jeff at sidefx.com
Fri Feb 2 14:03:15 EST 2007


Yeah, I guess your right... :)


-jeff

On Fri, 2007-02-02 at 12:35 -0500, Michael Goldfarb wrote:
> save it for the blog Jeff...sheesh...
> 
> :)
> 
> 
> 
> Jeff Wagner wrote:
> > I would assume that a Houdini unit is whatever you want it to be and
> > build your tools accordingly. Steven refers to the units that are
> > critical to DOPs when he mentions that a unit = 1 metre. Yes it is in
> > the Preferences and was added for DOPs but that's all. A nice guideline
> > but certainly not gospel.
> > 
> > A houdini unit is whatever you want it to be. 
> > 
> > Nothing is guaranteed with universal units. Units are cheated all the
> > time. Many times in many facilities modelling many props with all kinds
> > of different modelling tools, I have observed modellers delivering
> > props, characters and sets in vastly different scales/units on the same
> > job. It's a fact of life. Drives some TD's nuts. Others take it in
> > stride and build the support needed and move on. 
> > Tweaking scales of props, sets and other parts of a scene is an on-going
> > issue. Units are also changed if the scene is too large or too small so
> > you can work with it. Steven also mentioned this.
> > 
> > 
> > You should design your effects tools in such a way that you have a
> > single global scale parameter that properly scales the effect up and
> > down keeping both the behaviour and any shader patterns and other
> > scale-dependent parts properly aligned.
> > 
> > It is doable but requires some management as you build your effects
> > tools. If this is for general consumption, it is worth it.
> > 
> > In shaders that use procedural patterns, you can control globally within
> > the shader how to control the scale up and down. Helps to use "rest"
> > attributes. Same with SOPs.
> > 
> > Particle sims are trickier but you can with trial and error get the same
> > behaviour as you scale the environment that the sim is in.
> > 
> > DOPs isn't so easy. You pretty much have to scale things down then up
> > again going in to DOPs. Then again I haven't tried to build scalable
> > sims in DOPs yet. I would imagine that RBD sims would be easier to work
> > around than Cloth, wires, etc.
> > 
> > 
> > -jeff
> > 
> > On Fri, 2007-02-02 at 06:10 -0800, steven ong wrote:
> > 
> >>Hi Luca,
> >>
> >>A general rule of thumb is 1 m/unit in Houdini. When you read in
> >>geometry from Maya, they will be hundreds of units in Houdini because
> >>Maya is using 1cm/unit.
> >>
> >>Unless the scale is so big that you get into precision errors, no need
> >>to rescale either way, just work with the geometry as it is.
> >>
> >>Cheers!
> >>steven
> >>
> >>
> >>
> >>
> >>>Hello,
> >>>
> >>>I'm planning to create a library of effects all based on the same
> >>>scene
> >>>scale to be used in different shots (wispy snow, snowstorm, rain etc.
> >>>etc.).
> >>>I receive the camera and the geometry cache in worldspace from maya
> >>>for
> >>>collisions emitters etc. etc.
> >>>Is there a rule of thumb on what units use in houdini?
> >>>Also do you rescale the maya assets down to a more convenient houdini
> >>>scale, or do you do the other way around?
> >>>
> >>>thanks
> >>>Luca
> >>>
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> >>
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-- 
Jeff Wagner, jeff at sidefx.com, Senior Technology Consultant
Side Effects Software, www.sidefx.com, Toronto, Ontario, M5V 3E7
tel: (416) 504-9876, fax: (416) 504-6648

OldSchool Blog:
http://www.sidefx.com/index.php?option=com_content&task=blogcategory&id=115&Itemid=216



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