[vtk-developers] Rendering Corruption Due to PC Time Change

Elvis Stansvik elvis.stansvik at orexplore.com
Mon May 8 12:25:06 EDT 2017


Den 8 maj 2017 1:45 em skrev "Will Schroeder" <will.schroeder at kitware.com>:
>
> I love this bug! The more the esoteric bugs we have time to chase, my
obviously biased conclusion is that the better the quality of VTK's core
functionality is :-)
>
> I would enjoy seeing screenshots. I assume they would be public and we
would be able to use them elsewhere? Of course with appropriate credit...

I second that. Would love to see what you're up to. We're using VTK for
visualisation of the result coming from our xray based drill core scanner,
so sort of in the mining field as well. Though obviously our machine is
puny compared to yours :)

Elvis

>
> Best,
> W
>
> On Mon, May 8, 2017 at 7:25 AM, Paul <paul at 3dimageautomation.com.au>
wrote:
>>
>> Hi,
>>
>> We are using VTK in a 3D LiDAR based mining automation application which
operates continuously.
>>
>> VTK in medical application is great but VTK controlling the world’s
largest autonomous machine is interesting for engineering types.
>>
>> If anyone is interested we can post some screenshots.
>>
>>
>>
>> Many of the vtk developers will remember the vtk code impact of our
original issue with overflow of ModifiedTime on a Win64 build.
>>
>> Thanks again for the effort, it was certainly a relief as it was so
critical for our application success.
>>
>>
>>
>> Subsequent to the overflow fix the application has been running without
issues on two system equipped with dual Xeon processors.
>>
>> However one system with a four core i7 was having rendering issues at
intervals of a week or more.
>>
>> Our initial thoughts was that the issue was related to high processor
loading.
>>
>>
>>
>> It turns out that the issue is related to ModifiedTime.
>>
>> Rendering breaks if the PC time is changed in a negative direction.
>>
>>
>>
>> It took us some time to discover this.
>>
>> The i7 system is running Windows 7 and the Windows Time service was in
the Scheduled Tasks to run once a week on Sunday morning.
>>
>> Vtk rendering only breaks if the time synchronisation has a negative
correction.
>>
>> This can be reproduced by manually changing the PC time backwards.
>>
>>
>>
>>
>>
>> Q. Could this be resolved by making ModifiedTime independent of the PC
clock.
>>
>> We run a PLC (real time automation controller) in kernel mode on the
same platform.
>>
>> PLC’s are used in time critical applications such as motion
synchronisation and use a SystemTime that does not jump.
>>
>> I am not sure what mechanism the PLC uses but suspect that the time is
initialised to the PC time on application start and then incremented at
100nS intervals (the timer resolution).
>>
>>
>>
>> Paul
>>
>>
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>
>
>
> --
> William J. Schroeder, PhD
> Kitware, Inc. - Building the World's Technical Computing Software
> 28 Corporate Drive
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>
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