<div dir="ltr">For Virtual Reality and 4K/5K displays I believe ImageSampleDistance (or similar adjustable X,Y sample rate) has to be supported. Not sure when it will get implemented but I personally think it is necessary.<div><br></div><div>Thanks</div><div>Ken</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Feb 14, 2017 at 1:52 AM, Elvis Stansvik <span dir="ltr"><<a href="mailto:elvis.stansvik@orexplore.com" target="_blank">elvis.stansvik@orexplore.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">2017-02-13 17:10 GMT+01:00 Sankhesh Jhaveri <<a href="mailto:sankhesh.jhaveri@kitware.com">sankhesh.jhaveri@kitware.com</a>><wbr>:<br>
> Hi Elvis,<br>
><br>
> The ImageSampleDistance property was left out when coming up with the new<br>
> OpenGL2 volume mapper to avoid an additional step of rendering the volume to<br>
> an FBO and then using the texture to compute the scaling. This simplifies<br>
> the code path and reduces the extra performance overhead. The documentation<br>
> could have been better on this. We'll update it.<br>
<br>
Ah, that explains it.<br>
<br>
><br>
> That being said, do you have a specific use case for ImageSampleDistance? We<br>
> could explore options for adding the feature back in.<br>
<br>
I don't have a specific use case for it really. The reason I started<br>
looking into how the auto-adjustment works is that I've found it to be<br>
a little too aggressive in reducing the quality. I found that if I<br>
turned off auto-adjustment and hardcode the sample distance, I could<br>
get acceptable interactive frame rate at reasonable zoom level with a<br>
quality that looked better than what happens when the auto-adjustment<br>
kicks in. So I started looking at how the auto-adjustment works, and<br>
if perhaps I could make my own heuristic for degrading the quality. I<br>
was thus interested in what knobs for quality were available to me.<br>
<br>
I think what I'm really looking for is some way of setting a lower<br>
bound on the actual sample distance along the ray<br>
(ActualSampleDistance internally), similar to<br>
MinimumImageSampleDistance but for the sample distance.<br>
<br>
Has anyone else found that the auto-adjustment is seemingly a bit too<br>
aggressive? I'm keeping the desired frame rate of the render window at<br>
the default (15 fps I think), but the quality during interaction<br>
degrades to an unnecessary extent I think..<br>
<br>
Elvis<br>
<br>
><br>
> Thanks,<br>
> Sankhesh<br>
><br>
><br>
> On Mon, Feb 13, 2017 at 6:55 AM Elvis Stansvik<br>
> <<a href="mailto:elvis.stansvik@orexplore.com">elvis.stansvik@orexplore.com</a>> wrote:<br>
>><br>
>> 2017-02-13 12:54 GMT+01:00 Elvis Stansvik <<a href="mailto:elvis.stansvik@orexplore.com">elvis.stansvik@orexplore.com</a>><wbr>:<br>
>> > I was digging through the code trying to understand how the<br>
>> > auto-adjustment of sample distance and image sample distance takes<br>
>> > place in the GPU volume ray cast mapper. From the looks of it, the<br>
>> > ImageSampleDistance is not respected by this mapper, even in the<br>
>> > non-automatic case, or am I missing something?<br>
>><br>
>> Sorry, with "non-automatic case" I mean when AutoAdjustSampleDistance is<br>
>> Off.<br>
>><br>
>> Elvis<br>
>><br>
>> ><br>
>> > The only role ImageSampleDistance seems to play for this mapper is<br>
>> > when the reduction factor is calculated (when auto-adjustment is<br>
>> > turned off):<br>
>> ><br>
>> > if ( !this-><wbr>AutoAdjustSampleDistances )<br>
>> > {<br>
>> > this->ReductionFactor = 1.0 / this->ImageSampleDistance;<br>
>> > return;<br>
>> > }<br>
>> ><br>
>> > Elvis<br>
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><br>
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><br>
> Sr. Research & Development Engineer | Kitware | <a href="tel:%28518%29%20881-4417" value="+15188814417">(518) 881-4417</a><br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature">Ken Martin PhD<div>Chairman & CFO<br>Kitware Inc.<br>28 Corporate Drive<br>Clifton Park NY 12065<br>518 371 3971<div><br></div><div><span style="font-size:10pt;font-family:Tahoma,sans-serif">This communication,
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