Motion blur and hair

Tue May 23, 2017 8:37 am

I can't really figure out how hair and motion blur works, wondering if any other users are sharing this problem.

I have a fast moving mesh (butterfly) which is point cached, the hair on the mesh isn't dynamic, it's vertices don't move independently of each other. If I set motion blur to transform in the octane object tag- it doesn't blur correctly, and shows the mesh underneath and just looks really odd. Only way to get it looking right is using transform/vertex motion blur on the hair which increases my render times by about 5-10 times a 8 min frame turns into a 1hr30 min frame - this seems unnecessary seeing as the hairs move but the hair vertices don't. Also, unless I check "Force updates in picture viewer" the hair lags behind the mesh by several frames.

Can't really make sense of this.

Tue May 23, 2017 8:59 am

What's that you didn't get?

If you have "transform", we just export transform key frames for generating motion blur.
With "transform/vertex", we export transform+vertex keyframes.

If it lags a lot, check where it happens. After updating text appeared or before? If it's after then it's about heavy calculations for generating ray accelerators.

Also if you need to use "force updated ...." option this means that meshes/hairs are not triggered for changes and plugin cannot detect any updates to re-generate meshes for next frames. This is the mechanism of plugin to work.

Tue May 23, 2017 9:02 am

So why do I need vertex motion blur for correct looking motion blur of hair, when the hair vertices don't move, only the individual hairs in world space?

Hair is not dynamic and applied to a pointcached mesh...

Tue May 23, 2017 9:05 am

renderingz wrote:So why do I need vertex motion blur for correct looking motion blur of hair, when the hair vertices don't move, only the individual hairs in world space?

Hair is not dynamic and applied to a pointcached mesh...

Propably. I don't know how you produced but if it's like not having transform animation but just vertex animations.

Tue May 23, 2017 9:07 am

I'm just trying to figure out if there is a way around it, the mesh deforms, but again the hair isn't dynamic, so the hairs only change position/rotation. Is this the behaviour you would expect?

Could it be that individual hairs aren't treated as separate objects by Octane's motion blur engine? Hence not recognising transforms, that would explain this not working as expected...

Tue May 23, 2017 9:09 am

renderingz wrote:I'm just trying to figure out if there is a way around it, the mesh deforms, but again the hair isn't dynamic, so the hairs only change position/rotation. Is this the behaviour you would expect?

It may not be as your expectations in background process. If it's only working fine with "transform/vertex" that's the way to go. Also see/read this picture for a hint.

Tue May 23, 2017 9:13 am

Ok I will try this - additionally would I be better off using subframe motion blur to reduce render times? The hairs really don't move much.

Tue May 23, 2017 9:32 am

renderingz wrote:Ok I will try this - additionally would I be better off using subframe motion blur to reduce render times? The hairs really don't move much.

Can i get this scene to investigate?

Tue May 23, 2017 10:06 am

Yes, I'll send you the scene, is it helpful for you have with or without textures? scene comes in at 0.98GB compressed with textures. Also do you have an email so I can wetransfer?

Tue May 23, 2017 10:09 am

renderingz wrote:Yes, I'll send you the scene, is it helpful for you have with or without textures? scene comes in at 0.98GB compressed with textures. Also do you have an email so I can wetransfer?

I don't think that's a matter of textures. Just send me without those if you're agree.