[Sidefx-houdini-list] houdini -> mental ray user datas

Guy Rabiller guy at alamaison.fr
Thu Mar 23 02:03:59 EST 2006


That makes sense, yes, I'll have to check the geo format out, and 
experiment with all the ideas.

Thanks for your help Colin.

Cheers.
--
guy rabiller | 3d technical director @ LaMaison



Colin Doncaster a écrit :
> Hey dude -
>
> No worries, that's what the unix sop is handy for.  You can pipe your 
> current objects data to an external script, check out the help for it 
> and there is a user note from lucas that describes it in better detail.
>
> So you'd have a python script that accepts houdini's geo ascii format 
> as input ( from stdin ) and you can parse and format your data into 
> the .mi file.  If this is in your opnetwork ( I'd say make it your 
> render op ) you could then have it cooked on every frame prior to the 
> .mi file being written.  Because it's in your SOP level it will be on 
> a per object basis, you should be able to get all the custom 
> attributes in the geo file.
>
> To get the format spec for the geo format check out
>
> $HFS/public/GPD
>
> I don't think that the Attribute's you define on a SOP level are 
> passed through to the mi.  You can add some input parameters to you 
> script that handles specific cases for these attributes you know about.
>
> I'm tired, so I'm not to sure if that makes sense.
>
> Cheers - col.
>
> On 23-Mar-06, at 10:41 AM, Guy Rabiller wrote:
>
>>
>> Thanks Colin,
>>
>> that's a start for me, very interresting. I'll investigate.
>>
>> On a scene basis I can surely feed my custom datas through this 
>> inclusion mechanism.
>>
>> Now I have to figure out how to make the link between those datas and 
>> a specific object instance.
>> By any chance, do you know if this mechanism is available on a per 
>> object basis ?
>>
>> Looking at the Shading tab of a model, there is a mental ray sub-tab, 
>> where we can set mental ray shaders.
>>
>> Idealy, I'm looking for the same idea but for the object description 
>> itself, or mental ray 'attributes', may be a SOP node in wich we 
>> could set mental ray attribute for this object ( or light, or camera, 
>> etc.. )
>>
>> For instance a mental ray object Instance has attribute such as 
>> 'hide' (on/off), 'shadow' (mode) and even 'data' ( data name ), the 
>> one I'm interrested in.
>>
>> May be I'm just overcomplicating things ? If I put an Attribute SOP 
>> and use 'hide'/'on' it will be transmitted as this to the mental ray 
>> instance description ?
>> Could it be that simple ?
>>
>> I didnt try real exemple yet, I'm just trying to globaly figure out 
>> the right way(s) to reproduce ( and extend ) the type of workflow we 
>> currently have with XSI / mental ray.
>> ( still very new to Houdini )
>>
>> -- 
>> guy rabiller | 3d technical director @ LaMaison
>>
>>
>> Colin Doncaster a écrit :
>>>
>>> hey guy -
>>>
>>> each model has the pre and post include script which does get 
>>> written out to the .mi file.  You could write a pre-frame script ( 
>>> in the mental ray ROP ) that runs a script to generates an .mi file 
>>> for that frame and then set the pre/post include to that output.
>>>
>>> You can open a command port or stuff all the relevant object 
>>> information onto the command line to get scene data.
>>>
>>> It's ugly ( ish ) but it should work.
>>>
>>> Oh, the other thing that occured to me, if you put a unix sop at the 
>>> end of your sop network you could then pipe all the geometry data to 
>>> a script that formats it into the per frame .mi you want which means 
>>> you won't have to worry about the pre frame script in the output ROP.
>>>
>>> Just some thoughts.
>>>
>>> Cheers - colin.
>>>
>>> On 23-Mar-06, at 1:52 AM, Guy Rabiller wrote:
>>>
>>>> Hi,
>>>>
>>>> regarding mental ray rendering from within Houdini, is there any 
>>>> built-in mechanism to transfert "user-datas" to mental ray 
>>>> scenes/shaders ?
>>>>
>>>> In XSI for instance, there are what so called "UserDataBlobs" at a 
>>>> scene or object level, wich can be 'filled' by ascii datas from 
>>>> script or ascii/binary datas from c++ plugins.
>>>> Then at render time, XSI automatically send those datas as user 
>>>> datas ( miQ_OBJ_DATA.. ) attached to the object containing the 
>>>> UserdataBlob.
>>>>
>>>> Is there such mechanism in Houdini ?
>>>>
>>>> If not, what could be the best way to handle this, to enable user 
>>>> datas communication between Houdini and mental ray ?
>>>>
>>>> Thanks in advance.
>>>>
>>>> --guy rabiller | 3d technical director @ LaMaison
>>>>
>>>>
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>>>
>>> --Colin Doncaster Some Guy -- colin.doncaster at rsp.com.au
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>>
>>
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>
> -- 
> Colin Doncaster Some Guy -- colin.doncaster at rsp.com.au
> ----------------------------------------------------------------
> rising sun pictures -- http://www.rsp.com.au/
> ----------------------------------------------------------------
> direct line +61 (0)2 9338 6432
> mobile ph +61 (0)4 1011 1709
> ----------------------------------------------------------------
> syd ph +61 (0)2 9338 6400 -- fx +61 (0)2 9338 6401
> 15/16 charles street, redfern, sydney, nsw 2016
> ----------------------------------------------------------------
> adl ph +61 (0)8 8400 6400 -- fx +61 (0)8 8400 6401
> level 1, 133 gouger street, adelaide, sa 5000
> ----------------------------------------------------------------
> rising sun research - http://www.risingsunresearch.com/
> ----------------------------------------------------------------
>
>
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