Understanding motion blur subsamples

V-Ray for 3ds Max V-Ray for 3ds Max :: General
1

I’m just wrapping my head around motion blur subsamples, and I was wondering if anybody could help me confirm or refute that this is how this works:

Lets say each black notch here represents a frame, and each red notch represents a subframe that is being sampled for half a frame of motion blur. First black notch is f0.0, second black notch is f1.0 (where the playhead is placed) and the third is f3.0.

no motion blur, f1 is sampled:
|------------|------------|

Using MB with two geometry samples, frames f0.75 and f1.25 are sampled, like so:
|---------|---|---|---------|

For three geometry samples it’s f0.75, f1.0, f1.25
|---------|---|---|---------|

For four geometry samples, f0.75, f0.9166…, f1.166…, f1.25
|---------|--|-|-|--|---------|

…and so on. Does this seem accurate?

2

Yes, this is almost correct. There is a small mistake in the last row - should be f0.75, f0.9166…, f1.0833…, f1.25. This is for duration 0.5, as you said, and interval center 0.

Best regards,
Asen

3

You’re, I was having trouble with the math there. Good to know the rest is accurate, thanks.