Forums > Jitter

jit.gl.volume

February 7, 2006 | 6:59 pm

Hi,
I searched the archives, but didn’t find anything on this subject.
I’m using jit.gl.volume for visualizing some data right now and
noticed a few inconsistencies.

First, the range of values for intesity according to the help HTML doc
are implied to be [0, 1] when in fact they are [0, 255].

Second, the density and distance parameters do absolutely nothing on my system.

pb 1.67 osx 10.4.4 latest jit/max.

thanks,
wes


February 7, 2006 | 7:04 pm

PS, I was using the help patch.

wes


February 7, 2006 | 7:41 pm

On Feb 7, 2006, at 10:59 AM, Wesley Smith wrote:

> I searched the archives, but didn’t find anything on this subject.
> I’m using jit.gl.volume for visualizing some data right now and
> noticed a few inconsistencies.
>
> First, the range of values for intesity according to the help HTML doc
> are implied to be [0, 1] when in fact they are [0, 255].

Thanks for the mention. Actually it is unbounded for the maximum, and
as far as viewing is concerned depended on the number slices, and
perhaps other attributes. I suppose that the default value implies
the range, but nowehere is the range specified. Perhaps we can post
the formula used, which would be significantly more descriptive than
posting ranges of acceptable values.

> Second, the density and distance parameters do absolutely nothing
> on my system.

Hmmm. Same here. Perhaps these are legacy parameters based on an
earlier implementation. I think the distance is now implicit in the
object transformation, and I’m not sure what the difference between
density and intensity would be.

Thanks for the report.

-Joshua


February 7, 2006 | 9:14 pm

I’m not sure what the difference between
> density and intensity would be.
>

I would say density is a threshold for displaying info and intensity
is kind of like a limunance of the entire dataset. If this were the
case, then I would expect there to de a density mode 0/1 for
displaying everything below/above the given density value. What do
you think?

wes


February 7, 2006 | 9:47 pm

On Feb 7, 2006, at 1:14 PM, Wesley Smith wrote:

> I’m not sure what the difference between
>> density and intensity would be.
>>
> ‘
> I would say density is a threshold for displaying info and intensity
> is kind of like a limunance of the entire dataset. If this were the
> case, then I would expect there to de a density mode 0/1 for
> displaying everything below/above the given density value. What do
> you think?

Sounds appropriate to me, but I’ll need to find sometime to review
what is happening in this object and try to discern the intended
purpose of this feature, as the original developer, Derek, has moved
on to another employer. I’m not sure if I’ll find the time to do this
in the near future, but keep in mind that such a task can also be
accomplished with an object like [jit.op @op >p], jit.lumakey, or
jit.chromakey in the meantime.

Thanks,
Joshua


February 7, 2006 | 9:58 pm

> in the near future, but keep in mind that such a task can also be
> accomplished with an object like [jit.op @op >p], jit.lumakey, or
> jit.chromakey in the meantime.
>

True, but if the ops could be done in opengl via the opengl interface
available within jit.gl.volume which would be preferable. Obviously,
this will require some work, so I don’t expect this to be addressed
immediately. Just want to get it on the record.

wes


February 7, 2006 | 11:10 pm

On Feb 7, 2006, at 1:58 PM, Wesley Smith wrote:

> True, but if the ops could be done in opengl via the opengl interface
> available within jit.gl.volume which would be preferable.

This stuff is all happening on the CPU before the 3D texture is
dispatched to the GPU, so I don’t think it will have significant
performance difference except on really large matrices.

-Joshua


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