POV-Ray : Newsgroups : povray.advanced-users : Skewness (long) : Re: Skewness (long) Server Time
23 Jun 2024 06:03:00 EDT (-0400)
  Re: Skewness (long)  
From: Francois LE COAT
Date: 9 Nov 2018 09:00:10
Message: <5be592ea$1@news.povray.org>
Hi,

Bald Eagle writes:
> Francois LE COAT wrote:
> This is wonderful!   I'm glad you succeeded in working out the details 
for your
> specialized application.   And thanks for reporting back - it's always 
a
> pleasure to see the successes of interesting projects such as yours.  :
)

I've updated video <http://hebergement.u-psud.fr/lecoat/camera_fixe.mp4>
because in POV-Ray transformations, I shouldn't have used arc-tangent:
"
     matrix < 1 , 0, 0,
          atan(Sx*3.141592654/180.0), 1, 0,
           0 , 0, 1,
           0 , 0, 0 >
     matrix < 1,atan(Sy*3.141592654/180.0),  0,
          0,  1,  0,
          0,  0,  1,
          0,  0,  0 >
     rotate <Rx,Ry,Rz>
     translate <Tx,Ty,Tz>
"
but rather tangent:
"
     matrix < 1 , 0, 0,
          tan(Sx*3.141592654/180.0), 1, 0,
           0 , 0, 1,
           0 , 0, 0 >
     matrix < 1,tan(Sy*3.141592654/180.0),  0,
          0,  1,  0,
          0,  0,  1,
          0,  0,  0 >
     rotate <Rx,Ry,Rz>
     translate <Tx,Ty,Tz>
"
for skew along (x,y) axis. That means <Sx,Sy> skew (or shear) angles in
degrees are now better rendered. This is almost the same video, because
tangent and arc-tangent are similar for small skew (or shear) angles.

> If I may ask,  do you think your work is close enough to something like
:
> http://kevinkarsch.com/publications/sa11-lowres.pdf
> https://kevinkarsch.com/?page_id=445
> such that given a 2D photo, 3-dimensional parameters of objects in it c
ould be
> extrapolated from it?
> Perhaps you may find Dr. Karsch's computer vision research projects, an
d his
> source code, helpful in developing your own methods more quickly.  I my
self have
> been keeping an occasional eye on his work for several years now.

I'm trying to model the camera motion, if it's moving, and dominant
motion if the camera is static. This is a static camera in the video, so
I model head's movement. I'm not modelling the contents of the scene,
but rather the dominant motion. I'm modelling the optical-flow, meaning
a speed field of motion vectors between images. I'm not modelling
pixels, what POV-Ray is doing extremely well, indeed.

About the WEB page you're showing, it remembers me results of neural
networks I've seen recently, trying to model scenes, and synthesize ...

> I like your little yellow smiley face - I did a similar animated face a
 few
> years back.  :)

It's a smiley. I like it also because it looks like PacMan character :-)

> I hope to see more of your work - it looks like you are lucky enough to
 work on
> a very fun and enjoyable project.
> 
> All the best.
> 
> Bill Walker

You're welcome. You gave me good help, knowing advanced POV-Ray usage !

>> The interest with the method, is to evaluate large movements. It works
 !

Well, this is preliminary results ...

Thanks for your help,

Best regards,

-- 

<http://eureka.atari.org/>


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