[Sidefx-houdini-list] export 2d track to 3d

Ben Schrijvers ben.schrijvers at guerrilla-games.com
Mon Mar 17 13:33:16 EDT 2008


You don't need to creep. Just make your chop range node  -1024 to 1024 
and -778 to 778.
Or actually I would keep between -1 and 1 so that you don't end up with 
a really big geometry.
And attach that (the geo with your sops inside) to the camera like Louis 
says.

So X and Y are then controlled by the channels and when you move Z 
around you should be able to get a fit.
There is indeed a formula to get that fit done automaticly based on the 
camera settings... but I don't have that OTL installed at the moment.

cheers,
benS



jose fernandez wrote:
> Ok, but would you then bring in the grid into chops using a geometry 
> chop? Or what would you suggest to creep the point?
>
> Louis Dunlevy wrote:
>   
>> The short hacky answer is just parent it to the camera, make it the same 
>> aspect ratio as your plate and move it down z 'till it looks right! 
>> Works 99% of the time ;)
>>
>> I always use the same camera frustrum asset so I don't have to think 
>> about it too much.. all those numbers..
>>
>> jose fernandez wrote:
>>   
>>     
>>> How can I automatically fit a grid to camera, regardless of it's 
>>> distance on Z (what expression could I use)?
>>> Louis Dunlevy wrote:
>>>   
>>>     
>>>       
>>>> If you have the channels normalized in CHOPs all you need to do is fit a 
>>>> grid to the camera and creep a point driven by chops onto it. There are 
>>>> lots of ways to approach it but it kinda boils down to that type of thing..
>>>>
>>>> jose fernandez wrote:
>>>>   
>>>>     
>>>>       
>>>>         
>>>>> Well basically have a point in an arbitrary place in 3d space, that 
>>>>> moves proportionally in screen space as the 2d track. no matter where 
>>>>> the camera is...
>>>>>
>>>>> brian goodwin wrote:
>>>>>   
>>>>>     
>>>>>       
>>>>>         
>>>>>           
>>>>>> There many solutions to this,
>>>>>> but to get a better idea of what u are trying to achieve,
>>>>>>
>>>>>> are you trying to use the 2D track in 3 Dimentions or just have a flat plane
>>>>>> with locators that move on that flat place?
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Mon, Mar 17, 2008 at 3:09 PM, jose fernandez <
>>>>>> jose.fernandez at framestore-cfc.com> wrote:
>>>>>>
>>>>>>   
>>>>>>     
>>>>>>       
>>>>>>         
>>>>>>           
>>>>>>             
>>>>>>> Hi I'm trying to export a 2d track into 3d space. I've brought in the
>>>>>>> data through chops and fitted it to uv space (0-1) through a range node
>>>>>>> (1-2048 in x, 1-1556 in y).
>>>>>>> My first try was to use a grid at a certain point to project uv
>>>>>>> cordinates from camera... and transferring attributes between chops and
>>>>>>> the grid with point sops and finally a transfer attribute that copies
>>>>>>> color with the 3d information in it to the tracking point. In short this
>>>>>>> technique worked, but the metaball sampling doesn't seem to be accurate
>>>>>>> enough and while the point is at the expected position I get random
>>>>>>> jumps every few frames as it moves. I've tried playing with the kernel
>>>>>>> values but nothing makes it better.
>>>>>>> Could any ones suggest a more intelligent (and accurate) approach?
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>>>>>>>     
>>>>>>>       
>>>>>>>         
>>>>>>>           
>>>>>>>             
>>>>>>>               
>>>>>>   
>>>>>>     
>>>>>>       
>>>>>>         
>>>>>>           
>>>>>>             
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