[Sidefx-houdini-list] rectangular pbr area light

Robert Magee rmagee at sidefx.com
Tue Dec 11 13:33:47 EST 2007


You can also parent the light to a null object and scale the null object 
non-proportionally.

The reason that Scale is not on lights by default is that scaling lights 
can cause big problems for shadow generation when using depth map 
shadows (the same for cameras). People often scale lights and cameras to 
make them more visible in the scene and then the renderings don't work 
correctly. The scale icon parameter therefore lets you change the icon 
without affecting the shadowing.

If you choose to scale your lights (using null object or edit parameter) 
it should therefore only be used with raytracing and PBR style 
renderings. The null object will do the trick and should be used only 
when you are not using depth map shadows.

We will put an RFE in to offer a rectangle shape in the area light and 
offer two parameters for its size.

Robert

Luc Froehlicher wrote:
> Fred here show me the trick to do it:
> Edit Parameter - > create a new vector parameter called Scale (l_s)
> and in the Channels Tab -> Linked Channels type ./sx ./sy ./sz . it works
>
> another question about environment light :
> I noticed that NoAttenuation and HalfDistanceAttenuation  gives 
> different illumination.(this is without PBR)
> Physically correct is always black.
> is this correct ?
>
> Pablo Giménez a écrit :
>   
>> 2007/12/11, paul simpson <paul at realisestudio.com>:
>>   
>>     
>>> you welcome.  from what i remember mark telling me - you have to create a
>>> new light asset with scaling enabled.  however, it's bit of a hoop to jump
>>> through for such a common need.  i think that new users would find this
>>> unnecessarily complex.  maybe this is a good reason to have scaling
>>> allowable as default (MarkE)?
>>>
>>> i may be missing something obvious here.  i'd be keen to hear from sesi
>>> about "best pratice" on this issue - specifically dealing with area
>>> lights.
>>> i'm hoping that we'll have a nice suite of lighting tools and shaders for
>>> 9.1.  ie, uberlights, magic lights, and some bullet proof uber shaders
>>> (made
>>> out of lots of v useful mini shader assets).
>>>
>>> the quicker the power of mantra is opened up to the masses - the sooner
>>> houdini will receive the attention (and sales) that it deserves...
>>>     
>>>       
>> Complitely agree
>>
>> On 11/12/2007, Luc Froehlicher <lulu at alamaison.fr> wrote:
>>   
>>     
>>>> effectively if i parent the light under a null and scale the null it
>>>> works as expected
>>>> how do you add a scaling properties directly on the light ?
>>>> thanks paul.
>>>>
>>>> Mario Marengo a écrit :
>>>>       
>>>>         
>>>>> On December 11, 2007 06:14 am, paul simpson wrote:
>>>>>
>>>>>         
>>>>>           
>>>>>> ....or, just scale the light in x.
>>>>>>
>>>>>>           
>>>>>>             
>>>>> Heh... goes to show how much I use area lights... didn't even think to
>>>>>         
>>>>>           
>>>> try
>>>>       
>>>>         
>>>>> that! :)
>>>>>
>>>>> Thanks Paul.
>>>>>
>>>>> P.S: hmmm... the H9 lights don't have scaling properties available by
>>>>> default... I wonder why?... anyhoo... back to work
>>>>>
>>>>>
>>>>>         
>>>>>           
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>>>>       
>>>>         
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>>>       
>>
>>   
>>     
>
>
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-- 
Robert Magee
Product Marketing Manager
Side Effects Software Inc.
www.sidefx.com
416 504-9876 x327





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