[Bf-cycles] Motion Blur Implementation

Gavin Howard gavin.d.howard at gmail.com
Mon Jun 10 16:58:28 CEST 2013


     Does Blender allow exporting at arbitrary subframes? If not, that
might be a problem. If so, then Stuart has me exploring the code, and I
think that I could write the patch while doing so. Does that sound okay?

     God Bless,
     Gavin Howard
On Jun 9, 2013 6:34 AM, "Brecht Van Lommel" <brechtvanlommel at pandora.be>

> We should support exporting at the exact shutter time. At the time I
> implemented motion blur evaluation at subframes was actually broken
> for shape keys and physics systems so I didn't use it, but that has
> been fixed since.
> However, exporting motion from the frame positions may be useful to
> keep as it may give more predictable results in some cases. When
> you're editing animations that's the only thing you actually see in
> animation playback, so the motion between those frames may contain
> some unexpected things that you don't want to render.
> I don't know how common that is, did not look at .blend files yet to
> see how different the results are, if it is an issue we should
> probably have an option (off by default) to only export motion from
> integer frame numbers and no subframes.
> On Sat, Jun 8, 2013 at 7:36 PM, Gavin Howard <gavin.d.howard at gmail.com>
> wrote:
> >      Hello all,
> >
> >      I have a question about implementation. I have been told by
> > Brecht that currently, the Cycles addon exports three steps for motion
> > blur to the renderer: one at the previous frame, one at the current
> > frame, and one at the next frame.
> >
> >      Now, my memory may not be serving me well here, so I may have
> > gotten the details wrong. But if not, shouldn't the addon actually use
> > the shutter time to determine the first and third steps? For example,
> > shouldn't the addon export a step at the start of the shutter time,
> > one at the current frame, and one at the end of the shutter time?
> > Also, I think this type of reasoning should apply even when multi-step
> > (more than 3) motion blur is added. (Multi-step blur is needed for my
> > Deformation Motion Blur GSoC project, so I will add it over the
> > summer.)
> >
> >      In short, I think that the shutter time should be the goto for
> > exporting motion blur steps. If it is, then just ignore this. But if
> > it's not, should we change it? Anyway, that's my two cents.
> >
> >      God Bless,
> >      Gavin Howard
> > _______________________________________________
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> > Bf-cycles at blender.org
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