[Bf-cycles] Motion Blur Implementation

Gavin Howard gavin.d.howard at gmail.com
Wed Jun 12 06:50:09 CEST 2013

Hello all,

Okay, get ready for a long email because I have a few questions.

First of all, Brecht, you mentioned scene.frame_set(frame, subframe).
Subframe is between 0.0 and 1.0. Does that mean that I have to get the
previous frame and set subframes from there if I want to access
subframes BEFORE the current frame?

Also, I have found the part of the code that I need to modify to add
multi-step export. However, I have run into a snag: an unknown
variable. In the function BlenderSync::sync_motion() on line 473 of
intern/cycles/blender/blender_object.cpp, it has the for loop that
sets the frames. In the for loop, the controlling variable is called
motion. I have noticed that motion is used within functions called by
sync_motion(), like sync_camera_motion() and sync_objects(). I have
taken a look inside those functions, and I can't figure out what
motion is for, but I know that I can't modify its use without breaking
something. I would like to know what motion's purpose is. Maybe that
way I can figure out a way to modify its use safely, or maybe change
things around completely if necessary.

One last question: it is now BCon3, which is fixing only. No new
features. Technically, the patch that I am working on (using shutter
time for motion blur) could be considered a new feature. It will
definitely be a new feature if I add in multi-step export, which looks
like it could be very easy to add once I get this working. Brecht,
Ton, if I get this done before BCon4, could it still be added for
release? If so, should it be only the shutter time patch, or can I
include the multi-step export? (Oh, by the way, I have already
submitted a patch to change the UI for multi-step export.) If it
cannot be added for 2.68, should I submit it after release, or simply
put it into my branch to wait until my GSoC project is finished?

Hopefully that last paragraph made sense. If it didn't, let me know.

God Bless,
Gavin Howard

On Tue, Jun 11, 2013 at 9:32 PM, Gavin Howard <gavin.d.howard at gmail.com> wrote:
> Marco,
> I have the link. Thank you for finding that for me.
> This is very exciting! I have had a great response so far, and the
> official coding time has not even begun. Thank you all for your help!
> God Bless,
> Gavin Howard
> On Tue, Jun 11, 2013 at 3:40 AM, Marco Guzzetti
> <digitalbath86 at hotmail.com> wrote:
>> Hi Gavin,
>> from the BlendeArtist link I provide below, a developer from Appleseed make
>> a list with useful links regarding their Motion Blur implementation. Hope it
>> makes what you're looking for easier since he exactly links their MB source
>> code.
>> link -
>> http://www.blenderartists.org/forum/showthread.php?227830-Blender-2-6x-development-thread&p=2310497&viewfull=1#post2310497
>> _______________________________________________
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