[Sidefx-houdini-list] ray sop fetching attribute values thatdont exist.

François Duchesneau sidefx at trinix.ca
Wed Feb 3 19:10:25 EST 2010


I once had issues with it and the reason was because my model was huge. 
You will tell me that's what the bias is made for but I tried many 
different values without luck. I scaled it down, trace properly than 
scale it up to where it was and it worked a lot better.

I didn't know that triangulation will help. Good to know... let's hope I 
won't forgot when I face that kink of issue. Actually if you can send me 
a simple example of that I'd like to add it to the documentation.

Thanks

François

Simon Barrick wrote:
> I've found it's only really reliable on triangulated geometry.
> I believe that is because of the barycentric coordinates used to interpolate the values.
> I even had problems on a regular mesh grid until I triangulated it first.
>
>
> -----Original Message-----
> From: sidefx-houdini-list-bounces at sidefx.com on behalf of Andrew D Lyons
> Sent: Mon 01/02/2010 22:48
> To: sidefx-houdini-list at sidefx.com
> Subject: Re: [Sidefx-houdini-list] ray sop fetching attribute values thatdont exist.
>  
> How many samples are you using? Are you using "average Ray" as the
> combiner?You may be averaging multiple samples to get 0.
>
> If you play with some of those settings you may get more desirable
> results. ie. 5 samples and "longest ray".
>
> Cheers
>
> On 1 February 2010 14:39, Robert Kelly <isstuff at gmail.com> wrote:
>   
>> I am wondering if the ray sop can be trusted....
>>
>> I have a ray sop fetching attributes from some geometry but sometimes
>> it returns values that are not there to be returned.
>>
>> I have an int attribute called curve and it is on 7 tubes the
>> attribute goes from 1 to 7 according to the curve that each tube was
>> made from. The value is never zero. so i take that geometry append a
>> attributeCreate set the curve int value to -1. I put it into the first
>> input of a ray sop and the geometry before the attributeCreate into
>> the second input; I set the bias so it dosen't just get the same point
>> it came from... i set the ray sop to return the curve attribute that
>> it hits and the dist value.
>>
>> So i am getting Zero for some of the curve attributes, there are
>> plenty of -1 values for all the points that miss, and some values from
>> 1-7 for others that hit but some have 0 as the value. What could cause
>> this?
>>
>> Any ideas?
>> Robert Kelly
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>>
>>     
>
>
>
>   
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