After testing radiosity with this new scene, I'm rather afraid to modify it
for a hemispherical light source.

I have tried a few variations of motion blur with the system seen here. If,
anyone can tell me how to more realistically represent acceleration in the
blur, I would like to hear it!

Compression was not kind.

render time 23hr 34min. 24sec.

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Attachments:
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Preview of image 'InelNWrench.jpg'

GrimDude wrote:
> 
> After testing radiosity with this new scene, I'm rather afraid to modify it
> for a hemispherical light source.
> 
> I have tried a few variations of motion blur with the system seen here. If,
> anyone can tell me how to more realistically represent acceleration in the
> blur, I would like to hear it!
> 
> Compression was not kind.
> 
> render time 23hr 34min. 24sec.
> 

That looks very good, just a few things:

-The ground seems to be a plane with normal, maybe try an isosurface instead.
(would be more realistic with the shadows)

-The motion blur seems somewhat wrong, because both the right and the left ball
have the same blur, although the right one should move *before* the left one.

-Concerning the reflection i wonder what's above all this.

NTL great work

Christoph

--
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/

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GrimDude <vos### [at] yahoocom> wrote:
: I have tried a few variations of motion blur with the system seen here. If,
: anyone can tell me how to more realistically represent acceleration in the
: blur, I would like to hear it!

  You seem to have the same misconception about motion blur as most other
people have as well. The misconception is that the motion blur leaves a
trace behind the object, but the object itself is more or less sharp.
  I think that this is a consequence of artistic effects used in cartoons
(they draw lines in the path the obect has travelled to indicate that the
object is moving very fast). Although this artistic effect works for cartoons,
it has nothing to do with reality.

  In photography motion blur is caused by an object moving while the shutter
is open so that it leaves an equally weighted trace on the film. The reason
why it looks fainter than the static objects is that the light coming from
the moving object hits each point less time than static objects, thus
imprinting a dimmer "image" at that point. Some parts of the object look
semi-transparent because the object gets out of the way of whatever was
behind it (or the other way around).

  This means that if an object moves with a constant speed it leaves an
equally blurred trace on the film. The object is not sharper in one place
and more blurred in another.
  If the speed is not constant but accelerating, the amount of blur changes
as well, but still there's no sharp version of the object (unless it's most
of the time static and moves only a fraction of the time the shutter is open;
still this fraction of time has to be very small, like 1% to get a sharp
picture of the object).
  Specifically, with constant acceleration you get a constant (linear?) change
in the blur amount. This is the case of a falling object, for example.

  To get a photographically correct motion blur you should just define your
object with its motion path and let megapov do the rest. Don't try to
"correct" the calculations of megapov by adding additional static instances
of the object. If you do, you are just making a physically incorrect image.

  In this case your objects have quite complicated accelerated motions
(it's not even constant acceleration) so you should be precise in your math.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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Warp wrote:

>  You seem to have the same misconception about motion blur as most
>  other 
>people have as well. The misconception is that the motion blur leaves a
>trace behind the object, but the object itself is more or less sharp.
>  I think that this is a consequence of artistic effects used in
>  cartoons 
>(they draw lines in the path the obect has travelled to indicate that
>the object is moving very fast). Although this artistic effect works
>for cartoons, it has nothing to do with reality.
>

Two small notes,
In addition to the cartoon example, a lot of photos are a combination of a 
motion blurred object and a "static" one. In many cases a flash light is 
used in combination with a long slow shutter speed. It gives the sharp 
object with a blurred trail.

Something that sometimes can be seen is a deformation of the moving 
object. It's a result of the kind of shutter used in the camera. It can be 
a slit moving from left to right or top down. A top down moving slit can 
result in a car with oval wheels.

Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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Hey,

I have to say, your brass/gold spheres have one of the best metal textures I
have ever seen applied to them. Maybe it is the harsh lighting, but they
just seem ... so metaly! I'd love to see the code for the texture...

Equiprawn

GrimDude <vos### [at] yahoocom> wrote in message
news:39af6bb1@news.povray.org...
> After testing radiosity with this new scene, I'm rather afraid to modify
it
> for a hemispherical light source.
>
> I have tried a few variations of motion blur with the system seen here.
If,
> anyone can tell me how to more realistically represent acceleration in the
> blur, I would like to hear it!
>
> Compression was not kind.
>
> render time 23hr 34min. 24sec.
>
>
>

Post a reply to this message

"ingo" <ing### [at] homenl> wrote in message
news:8FA2BAA34seed7@204.213.191.228...
|
| In addition to the cartoon example, a lot of photos are a combination of a
| motion blurred object and a "static" one. In many cases a flash light is
| used in combination with a long slow shutter speed. It gives the sharp
| object with a blurred trail.

Leading and trailing flash is the technique I believe you're describing, to
get a either a blur ahead or behind the subject.  Shutter stays open after
the flash goes off or it closes just as it flashes.
In this case the shutter would have been opened before the flash has
occurred then promptly closed.
However, I agree with the observations that there would be more substance in
the blurs at the high points in the swings due to the slower movements there
(that was what was being said before, right?)

Bob

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If the plane uses normals, try isosurface instead. Right now it looks like a
plastic mat...
And ditto Warp yada yada yada

--
David Fontaine   <dav### [at] faricynet>   ICQ 55354965
Please visit my website:  http://davidf.faricy.net/

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On Fri, 1 Sep 2000 04:01:46 -0500, GrimDude wrote:
>After testing radiosity with this new scene, I'm rather afraid to modify it
>for a hemispherical light source.
>
>I have tried a few variations of motion blur with the system seen here. If,
>anyone can tell me how to more realistically represent acceleration in the
>blur, I would like to hear it!
>
>Compression was not kind.
>
>render time 23hr 34min. 24sec.

That looks great, are you sure it wasn't just an excuse to post
your wrinch again?


If you forget it's motion blur and concentrate on the inner balls
and chains it looks confusing, you wonder where the lines are 
coming from as they seem to be at the same angle as the lense flare
type highlights if you know what I mean.

-- 
Cheers
Steve              email mailto:ste### [at] zeroppsuklinuxnet

%HAV-A-NICEDAY Error not enough coffee  0 pps. 

web http://www.zeropps.uklinux.net/

or  http://start.at/zero-pps

 12:50am  up 11 days,  5:08,  2 users,  load average: 1.00, 1.00, 1.00

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Oooohhh.  Nice!

--
- Doug Eichenberg
  http://www.getinfo.net/douge
  dou### [at] nlsnet

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>   If the speed is not constant but accelerating, the amount of blur
changes
> as well, but still there's no sharp version of the object (unless it's
most

Right. What I was alluding to...

Cartoon physics aside... adding the 'frozen' objects was a temporary thing.
I suppose I didn't declare the period properly, or did something else silly,
but the blur that resulted from earlier tests was not what I was looking
for. In this scene I cheated, but for the blur I would expect a more elastic
appearance to the collision/motion (and of course non-conformity in the
extents). I will attempt another test over the next few days. I was really
looking forward to an animation, but this is starting to look like a week
long rendering. Particularly, if I finish the scene out the way I had in
mind. I mean after all! A twenty-four hour render is good enough reason for
a post. heh, (j/k)

I did a single element (gold ball) render at 1000 samples and recursion 3,
very low error, half-spheroid lighting, etc. and the result was amazing. I
can't wait to see the finished scene!

I know you could pull this off easy, Warp. :)

Grim

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