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[Manta] Re: Re: Re: RayPacketData::minT


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  • From: "James Bigler" < >
  • To:
  • Subject: [Manta] Re: Re: Re: RayPacketData::minT
  • Date: Wed, 10 Sep 2008 07:06:53 -0600
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What Abe is mentioning, is that the minT value is based on the length
of the direction vector.  When someone requests that the direction
vector be normalized, then minT is rescaled to keep it consistent.  In
addition this means that minT could have different "units" based on
the length of the direction vector.

If you want to compare minT with different rays, you should normalize
the ray directions with a call to RayPacket::normalizeDirections().

James

On Tue, Sep 9, 2008 at 5:49 PM, Abe Stephens 
< >
 wrote:
> Check the ray packet flag NormalizedDirections
>
> Abe
>
> On Sep 9, 2008, at 5:47 PM, Li-Ta Lo wrote:
>
>> On Tue, 2008-09-09 at 17:20 -0600, Thiago Ize wrote:
>>>
>>> Looking at Raypacket.cc we see:
>>>
>>> void RayPacket::actualComputeHitPositions()
>>> {
>>> <snip>
>>>       for(int i = rayBegin; i < rayEnd; i++){
>>>               for(int j=0;j<3;j++)
>>>                       data->hitPosition[j][i] = data->origin[j][i] +
>>> data->direction[j][i] * data->minT[i];
>>>       }
>>> <snip>
>>> }
>>>
>>> So, minT is what goes in the ray equation.
>>
>> Is data->direction normalized? Can I compare minT between rays with
>> different directions and still say T1 > T2 so point 1 is further to
>> the eye than point 2?
>>
>> Ollie
>>
>>
>
>

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