[Sidefx-houdini-list] DOPS and scale

Robert Kelly isstuff at gmail.com
Tue Jan 18 17:06:03 EST 2011


you fall at a rate of 9.8 m/s² if your unit scale is  1 unit = 1 meter
then you put in your gravity force 9.8
BUT !
if your unit scale is 1 unit = 1 center meter other wise known as 1
unit = .01 Meters then your gravity force gets a value of 980.

There are other real world values that are unit sensitive.

http://en.wikipedia.org/wiki/Equations_for_a_falling_body

On 18 January 2011 13:50, Alex Czetwertynski <disciple1 at gmail.com> wrote:
> Thanks for the answers...
>
> What nodes are scene unit sensitive?
>
> Thanks
> Alex
>
> On Jan 18, 2011, at 1:46 PM, Robert Kelly wrote:
>
>> if your doing DOPs you want to set your unit scale before putting down
>> any DOP nodes. They change values on the nodes that are scene unit
>> sensitive on creation. So if your not careful you can make a scene
>> with some values made for meters and some set for center meters.
>>
>> On 18 January 2011 09:08, Michael K. O'Brien <mobrien at pixar.com> wrote:
>>> Hola~
>>>
>>> There are several constants in physics simulations that have dependencies on
>>> distance that aren't exposed (like damping factors). If you try to do really
>>> large or small scale simulations, float precisions starts to creep in as
>>> well.
>>>
>>> We usually scale the world down so something that is 1 unit == 1m when
>>> possible. We've had problems with changing the units.
>>>
>>> MO
>>>
>>>> -----Original Message-----
>>>> From: sidefx-houdini-list-bounces at sidefx.com [mailto:sidefx-houdini-
>>>> list-bounces at sidefx.com] On Behalf Of Peter Bowmar
>>>> Sent: Monday, January 17, 2011 8:19 PM
>>>> To: sidefx-houdini-list at sidefx.com
>>>> Subject: Re: [Sidefx-houdini-list] DOPS and scale
>>>>
>>>> I believe 1 unit defaults to 1 metre and 1 weight unit is Kg (forget
>>>> exactly). It's in the Preferences->Miscellaneous section. So the
>>>> "smaller object" would have lower mass and therefor less force
>>>> required to accelerate it.
>>>>
>>>> Unless I've really badly forgotten my highschool physics :) in which
>>>> case I blame the antibiotics...
>>>>
>>>> Cheers,
>>>>
>>>> Peter B
>>>>
>>>> On 17 January 2011 19:00, Alex Czetwertynski <alex at franktheplumber.com>
>>>> wrote:
>>>>> When modeling objects to be used in DOPS, does one have to pay
>>>> attention to scale?  I noticed a wind force had a much stronger
>>>> influence on a smaller object, but I'm not sure what the rule of thumb
>>>> is in terms of getting things to be in a good mid-range?
>>>>> staying within the range of the initial grid maybe?
>>>>>
>>>>> Thanks
>>>>> Alex
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>>>>
>>>>
>>>>
>>>> --
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