Mo Blur Not Working

[pali_rao]

Thanks for investigating!

I rolled back to a previous version, and mo blur works fine with a VRay Physical Camera, BUT if I add a VRay ObjectProperties to ANY object in the scene, it stops working (even if I don't change any values at all).

If I go back to a standard camera, and turn on Motion blur in the overrides, it works, but if I increase the motion blur samples, it stops mo blur again.

I need to be able to increase the mo blur samples somehow - please could someone advise?

Thanks

[pali_rao]

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[pali_rao]

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[pali_rao]

Im not convinced that VRay Motion Blur is working properly at all. Please see attached image of a spinning cube with VRay Physical camera and motion blur enabled. No matter what shutter speed, there is no blur at all on the production render.

[pali_rao]

Is there a workaround for getting the motion blur samples on my original file working? Is there a previous version of VRay where this works?

[pali_rao]

This may help illustrate the issue - just adding a VRay Object Properties tag (and not changing anything) k ills motion blur - a bug?

[aleksandar.kasabov]

Hello pali_rao,

Would you mind also sharing the scene with me so I can have a look? Thank you.

[sirio76]

Hello pali_rao,

Would you mind also sharing the scene with me so I can have a look? Thank you.

Hi Aleksandar,
I tested the scene and I've created a new one as well, there is definitely something wrong with the motion blur sample system.
Increasing the number from 2 to a larger number create progressively wrong results. It looks like the effect become increasingly more transparent and in same case became almost invisible.
I can reproduce this on both Vray6 and 5 and C4D R25/26, works like that in every scene, here is a simple setup:
cube mb.c4d

A couple test render with relative velocity channel.
Motion blur sample = 2:



Motion blur sample = 16:

[pali_rao]

Hello pali_rao,

Would you mind also sharing the scene with me so I can have a look? Thank you.

Thanks Aleksandar - I have emailed you the scene file. Im using VRay 6 on C4D 2023, but was getting the same results with C4D R26 and VRay 5.

Thanks sirio76 for investigating!

[pali_rao]

I can get the scene to render with mo blur successfully, but if I add a VRayObjectProperties tag to anything, without changing a thing, the mo blur goes away.

[boyan]

Hey, Sirio, Pali,

Thank you for your excellent, fantastic support. I am almost 98.0% sure this is the correct behavior when using 16+ geometry samples. This is how it has worked since V-Ray Next.

Cheers,

[pali_rao]

Thanks to you too Boyan - but this issue happens without changing ANYTHING in the VRayObjectsProperties, so even with 0 geo samples - just adding the tag stop mo blur from working. Please check out the attached image from above.

[sirio76]

Hey, Sirio, Pali,

Thank you for your excellent, fantastic support. I am almost 98.0% sure this is the correct behavior when using 16+ geometry samples. This is how it has worked since V-Ray Next.

Cheers,

Hi Boyan, this can not be right, for example in the car scene the motion blur became almost invisible with more samples. Since more samples may be needed for spinning parts like the wheels the mb is not usable. I will check also with an older scene with a propeller that worked for sure to see if something has changed.

[pali_rao]

Hi Boyan, this can not be right, for example in the car scene the motion blur became almost invisible with more samples. Since more samples may be needed for spinning parts like the wheels the mb is not usable. I will check also with an older scene with a propeller that worked for sure to see if something has changed.

I agree totally - I can get mo blur to work, but it does not seem possible to get more samples, as when you add a VRayObjectProperties tag, mo blur stops. Also this is whilst using a VRay Physical Camera with mo blur enabled.

[sirio76]

boyan aleksandar.kasabov shaio

This is the final result obtained with a movie camera for reference: https://www.youtube.com/shorts/hh16F_Xfqhs

Here is a test on a single frame, this is what I get using a movie and a still camera with no motion blur samples.

Movie camera no samples:



Still camera no samples:



As you would expect the motion blur is fine but the propeller do not have a correct "circular" motion blur because you do not have enough samples.
So you increase the samples, I've used 16 here and this is what I get.

Movie camera 16 samples:



Still camera 16 samples:



Without the additional samples both movie and still camera produced very close results that feels correct beside the propeller issue, once you add more samples with the object properties tag the movie camera works great and you get a correct motion blur on the propeller, while on the still camera the result is much different and in my opinion simply wrong.

pali_rao the good news here is that the movie camera worked perfectly so yo can use that and you will get perfect results.