[Bf-cycles] Extraction of Motion Information

Michael Ortner fau at michael-ortner.de
Mon Dec 5 13:11:30 CET 2016



I'm a student at Friedrich Alexander University in Erlangen. I was tasked to
extract motion information for both, Perspective Camera and Fisheye Camera.
That can greatly help in the development of Video coders such as HEVC, to
test new algorithms for motion estimation and compensation. The initial
tests showed the great potential that Blender has to offer in that area of

I could use some help on the motion extraction part. For weeks now I'm
trying to understand the relevant parts of the source code. 


I was able to use the Vector Motion Pass to extract the motion vectors for x
and y motion using the Compositor. The relevant file is the
geom_primitive.h. The part I have trouble with, is to extract the z-motion.
Motion of the objects in depth in relation to the camera. 

It seems that tfm = object_fetch_vector_transform(kg, ccl_fetch(sd, object),
OBJECT_VECTOR_MOTION_PRE); does not contain the information I need for the

So consequently motion_pre = transform_point(&tfm, motion_pre); only returns
the previously initialized value form center. Of course, then the z-motion
in the end is zero.


Now, I tried to track down where that relevant information is initialized,
but had no luck so far. At some point I hit a wall, because that entire
split kernel setup confuses me. I'm not that experienced in programming in a
project of that magnitude. So I would greatly appreciate if someone could
point me in the right direction. After weeks of digging through the code I'm
not ashamed to admit that I need help with that.


I'm looking forward to hearing from you




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