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Rendering Corruption Due to PC Time Change

Paul-2

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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Re: Rendering Corruption Due to PC Time Change

Will Schroeder-2
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...

Best,
W

On Mon, May 8, 2017 at 7:25 AM, Paul <[hidden email]> 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
Clifton Park, NY 12065
[hidden email]
http://www.kitware.com
(518) 881-4902

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Re: Rendering Corruption Due to PC Time Change

Ken Martin
In reply to this post by Paul-2
I think Modified time is independent of the clock. I believe it is a 64bit integer that starts at zero and goes up by one each time something is modified by VTK. So maybe something else is going on here...

On Mon, May 8, 2017 at 7:25 AM, Paul <[hidden email]> 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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--
Ken Martin PhD
Distinguished Engineer
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065

This communication, including all attachments, contains confidential and legally privileged information, and it is intended only for the use of the addressee.  Access to this email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken in reliance on it is prohibited and may be unlawful. If you received this communication in error please notify us immediately and destroy the original message.  Thank you.

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Re: Rendering Corruption Due to PC Time Change

Paul-2

Hi,

We will check again and create a standalone test app if it is confirmed.

 

Thanks,

Paul

 

From: Ken Martin [mailto:[hidden email]]
Sent: Monday, 8 May, 2017 22:07
To: Paul <[hidden email]>
Cc: [hidden email]
Subject: Re: [vtk-developers] Rendering Corruption Due to PC Time Change

 

I think Modified time is independent of the clock. I believe it is a 64bit integer that starts at zero and goes up by one each time something is modified by VTK. So maybe something else is going on here...

 

On Mon, May 8, 2017 at 7:25 AM, Paul <[hidden email]> 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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--

Ken Martin PhD

Distinguished Engineer
Kitware Inc.

28 Corporate Drive
Clifton Park NY 12065

 

This communication, including all attachments, contains confidential and legally privileged information, and it is intended only for the use of the addressee.  Access to this email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken in reliance on it is prohibited and may be unlawful. If you received this communication in error please notify us immediately and destroy the original message.  Thank you.


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Re: Rendering Corruption Due to PC Time Change

Elvis Stansvik
In reply to this post by Will Schroeder-2

Den 8 maj 2017 1:45 em skrev "Will Schroeder" <[hidden email]>:
>
> 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 <[hidden email]> 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
>>
>>
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>>
>> Search the list archives at: http://markmail.org/search/?q=vtk-developers
>>
>> Follow this link to subscribe/unsubscribe:
>> http://public.kitware.com/mailman/listinfo/vtk-developers
>>
>>
>
>
>
> --
> William J. Schroeder, PhD
> Kitware, Inc. - Building the World's Technical Computing Software
> 28 Corporate Drive
> Clifton Park, NY 12065
> [hidden email]
> http://www.kitware.com
> (518) 881-4902
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>
> Search the list archives at: http://markmail.org/search/?q=vtk-developers
>
> Follow this link to subscribe/unsubscribe:
> http://public.kitware.com/mailman/listinfo/vtk-developers
>
>


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