Alain <kua### [at] videotronca> wrote:

> > Hm, I'm not quite sure, if this alone solves the issue of having motion blur
> > with POV 3.7. Should this wonderful superman not having decreasing transparency
> > during the flight? If you only average pictures of the flight, you will probably
> > get more blur than expected, since POV doesn't know the sequence of the
> > pictures. May be, proper weights in the average map will help. But you are still
> > limited to 256 entries. An other approach is to have copies of the blurred
> > object with decreasing transparency in the scene. But to find the correct
> > positions and transparencies is the hard job. Christian Froeschlin gave an
> > example with his entry "glocken" at the IRTC april 2006, which shows the idea
> > but the difficulties likewise (rendered at a higher resolution then the original
> > entry).
> >
> > Best regards,
> > Michael
> >
> >
>
> For the comicks like decreased transparency.
> In this sample scene, all frames have the same weight, but it can be
> changed:
>     #for(V, 1, n_frames)
>      [V // the weight goes from 1 to n_frames.
>       #declare image_name = concat(image_name_, str(V,
> -(log(n_frames)/log(10) +
> 1), 0))
>       image_map{image_type_() image_name}
>       translate -(x+y)/2
>      ]
>     #end
>
> By replacing the [1 by [V, the first image have a weight of 1, the
> second a weight of 2,...
> You can also use V/n_frames if you want to keep the weight parameter no
> larger than 1.
> You can increase the last image further in a few ways:
> Add some number to the last image's weight.
> Use pow(V,2) or pow(V/n_frames,2) for the weight. You can use a power of
> 3, 4 or some intermediate value if you want.
> This assume that each frame is created in the direction of the movement
> and that you want the last frame to dominate.
>
> The limit of 256 entries is not a problem unless you have a very long
> motion blur trail. If you use decreasing transparency, it's even less of
> a problem, even with rather long trails.
>
>
>
> Alain

Yes, your proposal is much more detailed than mine. In fact I only mentioned the
general idea that simply averaging pictures of a flight will not yield a motion
blurred picture and proper weights are needed. But I think you have to play
around a lot with the weights and the number of images to find a proper image.

Best regards,
Michael

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