Motion blur cheat mode for static objects

[JD3D_CGI]

So I always have certain objects that are static - people, cars, water fountains etc. and I would love a simple option to fake some motion blur - like some kind of render time vertex cache magic that allows Vray to treat them as if they are moving and generate a bit of blur.


I don't want to have to manually keyframe things and then render them this way, and thus I am wondering if there is a Vray trick that can be done?

Might be a time saver?

[^Lele^]

Well, in which direction should it blur them, and by how much?
I'd rather think that animating the previous and next frame to the actual view *is* the way to do it (and how i have always done it).
Or have i missed some obvious point?

[JD3D_CGI]

Well, some things like - I have a scene with water fountains made in Phoenix that I collapsed down to one object. So it would be good if they could have some kind of rudimentary blur applied.

[Ihno]

Well, some things like - I have a scene with water fountains made in Phoenix that I collapsed down to one object. So it would be good if they could have some kind of rudimentary blur applied.

Why do you collapse the sim? You'd get MB if you export the velocity channel and not collapse it. The mesh will be better than the (preview) mesh and give you more options for smoothing and stuff.

[Vizioen]

I also dread having to animate cars everytime to get the motion blur, but I wouldn't know how to cheat or I would've done it already. Some kind of modifier for very basic motion blur in the direction of some local object axis would be cool. Would be nice if you could specify the speed of the object in m/s or something with the moblur duration accessible through this modifier.

[Ihno]

And in the end you'd need 4-5 test renders to get the axis right and you'd still have no spinning wheels... I think It would be best to simply make an animated version and save it as an extra file so you only do it once per car.

[fixeighted]

Hmm...well for things like cars why not use a directional blur in P'shop or for more advanced motions a path blur? This can work well in many circumstances, even with guessing it.
More speed accuracy could be achieved by using AE to animate it I guess.
For a fountain I would personally play with a variation on that approach, if using the simmed geometry isn't an option.

[Vizioen]

And in the end you'd need 4-5 test renders to get the axis right and you'd still have no spinning wheels... I think It would be best to simply make an animated version and save it as an extra file so you only do it once per car.

Good idea actually, I could make a template even with a helper so I can just attach different cars.

[Buck]

you can use a motion vector / velocity channel and do motionblur in post. If that's what you're asking.

[^Lele^]

you can use a motion vector / velocity channel and do motionblur in post. If that's what you're asking.

I think that's what's *roughly* being asked.
I still do not understand how the motion vector data are being generated, from a static mesh that must not be animated across frames.

[Buck]

oh, uh.... nevermind. strange request.

[JD3D_CGI]

I think that's what's *roughly* being asked.
I still do not understand how the motion vector data are being generated, from a static mesh that must not be animated across frames.

Well, I';m not here to explain to you how to do it am I? - I'm here asking for it as a request.

Perhaps some kind of render-time movement calculation like a displacement map? - you right click an object or put on a modifier and at render-time is calculates as if the object has moved x amount of frames forward and backwards.

[JD3D_CGI]

Why do you collapse the sim? You'd get MB if you export the velocity channel and not collapse it. The mesh will be better than the (preview) mesh and give you more options for smoothing and stuff.

Because I'm working ona project where the client needs to use my files but also wont pay for Phoenix and even if they did it would be a mission to get it installed etc.

[^Lele^]

Well, I';m not here to explain to you how to do it am I? - I'm here asking for it as a request.

Indeed. Which is why i was asking for elucidations.

The modifier suggestion is unfortunately just the same, recursive question: where should the motion data come from?
Where was that mesh the frame before, and where should it be on the next one?

In the case of your water fountain, in the next frame, if the water was somehow correctly "moved" forward by the modifier, what would happen to the mesh at the emission points?
How would V-Ray fill in the gap formed there, given it'll influence the look of the motion blur at the current frame?

My experience at 2.5d motion blurring tells me that these kinds are unanswerable questions, ones which often end up leading to the hand painting of (many...) pixels.

I think it's truly a lot more efficient, and of course automatically accurate, to save your assets with a few frames per proxy, f.e., so to be able to both add variations to scenes, and motion blur those which need that treatment.

[Ihno]

Because I'm working ona project where the client needs to use my files but also wont pay for Phoenix and even if they did it would be a mission to get it installed etc.

Then you should be able to use the Vray Volume grid for that if I'm not mistaking. You can load the aur files there.
But rendering is free for phoenix anyways, you might be able to get away with a trail version for rendering.