VSS DHCP Jet Writer Experiences Errors During Backup with WBADMIN

Question

I'm trying to replicate a real-world camera within Three.js, where I have the camera's distortion specified as parameters for a "plumb bob" model. In particular I have P, K, R and D as specified here:

If I understand everything correctly, I want to set up Three to do the translation from "X" on the right, to the "input image" in the top left. One approach I'm considering is making a Three.js Camera of my own, setting the projectionMatrix to ... something involving K and D. Does this make sense? What exactly would I set it to, considering K and D are specified as 1 dimensional arrays, of length 9 and 5 respectively. I'm a bit lost how to combine all the numbers :(

I notice in this answer that there are complicated things necessary to render straight lines as curved, they way they would be with certain camera distortions (like a fish eye lens). I do not need that for my purposes if that is more complicated. Simply rendering each vertex is the correct spot is sufficient.

Solution

I resolved this by moving the start time forward 30 minutes for the weekly backup that was giving me problems. I looked diligently for some process that was running that would conflict with the original 12:00 AM start time but was unable to find one, yet the only conclusion I can draw is that something else was preventing the DHCP VSS writer from functioning when the backup started.

Comments

[BlueCompute]

What does the --% parameter do? Also, do you change the volume ID for the USB drive when you rotate it? Or...?

[I say Reinstate Monica]

@BlueCompute --% tells PowerShell to stop parsing the command so it doesn't return an error when commas appear in the -include or -exclude parameters. The disk GUID is changed when the USB drive is rotated. I didn't include the full script as it's over 100 lines of code.

[BlueCompute]

Ah, no worries, I missed the bit about it being run in powershell...

[Marquizzo]

What's a plumb bob?

[Eric Simonton]

In this case, it's the name of a "distortion model". There is some explanation of it here: calib.io/blogs/knowledge-base/camera-models

[Michele Lambertucci]

Yes, it makes a lot of sense to create your own Camera class, and it's not even a lot of work. One other thing you could consider is to do have the distortion you're talking about using a post-processing effect that performs only the radial distortion part, since it seems to only need image coordinates (as opposed to needing xyz coordinates)

[Eric Simonton]

@MicheleLambertucci Thank you. I am not familiar with post-processing effects, but I did notice them when looking for options. I was starting to think I may need to write some webgl code to achieve the radial distortion, which I think means it would be in such a post-processing effect? Do you know if that's true, or can that be represented in a projection matrix? Or is there some other option?

[Michele Lambertucci]

A post-processing effect is an additional shader pass applied over the rendered image. This is especially useful in this case, since the distortion you want to achieve works in "rendered space" (it doesn't need any information about the depth). Yes, I think you can use a simple GLSL shader to apply the radial distortion over the rendered image

[Eric Simonton]

Great! I have seen that reference, but I do not understand how use that to create a 4x4 projection matrix for a Three.js camera. Can you help answer that? I see the "camera matrix" that they define as KK, but that is 3x3 whereas Three.js uses a 4x4 matrix. Also, none of its values relate to the "distortion coefficients", so I'm not sure how it could be the only thing I need.