Here are a couple of features that should be included in POV-Ray 4.0

Bi-cubic texture filtering -- looks one hell of a lot better than bilinear,
I can't understand why this hasn't been added yet.

More transparency options for true colour image maps -- eg. set one colour
to transparent, allow loading of a transparency map.

Fixes for the glitches mentioned in the QandT section of the help files.

Fix for the photons glitch I mentioned in an earlier post.


Hopefully the POV-Team should be able to implement these in the next version
(although it would be nice to have a little update for v3.5 adding the
bicubic filtering).

If anyone else gets any ideas, how about posting them in replies to this
post? That would keep all the feature requests together, make things nice
and neat.

Rohan _e_ii

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In article <web.3d7c3fe93a4d0e17d02c7b870@news.povray.org> , "Rohan Bernett"
<rox### [at] yahoocom> wrote:

> Bi-cubic texture filtering -- looks one hell of a lot better than bilinear,
> I can't understand why this hasn't been added yet.

Because nobody implemented it yet?

> More transparency options for true colour image maps -- eg. set one colour
> to transparent, allow loading of a transparency map.

POV-Ray supports alpha channels in most image formats.  Please check the
documentation.

> Fixes for the glitches mentioned in the QandT section of the help files.
>
> Fix for the photons glitch I mentioned in an earlier post.

Why would these two be feature requests?  In the past, has each version of
POV-Ray not included fixes for bugs found in earlier versions or revisions?

Apart from this, you can hardly be less precise the way you formulated the
above...

> Hopefully the POV-Team should be able to implement these in the next version

Why not implement it yourself?  The source code is available, no need to
wait for the POV-Team ;-)

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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Rohan Bernett <rox### [at] yahoocom> wrote:
> Bi-cubic texture filtering -- looks one hell of a lot better than bilinear,
> I can't understand why this hasn't been added yet.

  I don't remember the exact algorithm of bicubic filtering, but I faintly
remember that it does not (necessarily) preserve the original colors of the
pixels at the center of the pixels (as for example bilinear filtering does).
This would mean that for example if you have a black image with one white
pixel in the middle, the white pixel would turn into a gray pixel after the
filtering.
  Of course this does not mean that a better filtering algorithm could not
be used. There are filtering algorithms which preserve the original colors
of the pixels (or at least get very close) while still looking a lot better
than bilinear filtering.

  Here is a set of images zoomed with ImageMagick using different filtering
options (14 in total). You can judge which looks best. (The 'triangle'
filtering is bilinear.)

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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Thorsten Froehlich wrote:
> 
> Why not implement it yourself?  The source code is available, no need to
> wait for the POV-Team ;-)

That raises a question: as the code isn't really open source, what's the 
official policy on blending contributed code back into the official 
source? Is there one? Or is it a strictly "we make the app, you make the 
patch" sort of thing, as the work up to and including MegaPOV suggests?

-Xplo

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"Warp" wrote:
>   Here is a set of images zoomed with ImageMagick using different filtering
> options (14 in total). You can judge which looks best. (The 'triangle'
> filtering is bilinear.)

url?
;-)

--
Jonathan.

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JRG <jrg### [at] hotmailcom> wrote:
> url?
> ;-)

  I must be getting old...

http://www.cs.tut.fi/~warp/filtering/

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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Hmm, that picture *does* show cubic interpolation blurring the pixels
together too much.

I always thought bi-cubic interpolation was really just bi-linear
interpolation with the points interpolated between in a smoother manner.
Like, if you graphed a row of pixels interpolated with bi-linear
interpolation, you'd have a bunch of points connected with straight lines,
but if you graphed it with bi-cubic interpolation, you'd have a bunch of
points connected with curves that match the curve

y = -2*x^3 + 3*x^2 = x^2*(3-2*x)

from x=0 to 1. (the second expression is equivalent but faster to calculate
with a computer, I believe. I took it from the noise generator source code.)

 - Slime
[ http://www.slimeland.com/ ]

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Thorsten Froehlich wrote:

>POV-Ray supports alpha channels in most image formats.  Please check the
>documentation.

I really meant loading the transparency map as a separate file.

>Why not implement it yourself?  The source code is available, no need to
>wait for the POV-Team ;-)

Unfortunatly, I have insufficent programming skills in C++ to be able to do
it. :-(

Rohan _e_ii

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>  I don't remember the exact algorithm of bicubic filtering, but I faintly
>remember that it does not (necessarily) preserve the original colors of the
>pixels at the center of the pixels (as for example bilinear filtering does).

This site has some info on interpolation methods

http://astronomy.swin.edu.au/~pbourke/curves/

Try the interpolation methods link, it has info on linear, cosine, cubic,
and somehthing called Hermite interpolation. This Hermite interpolation
seems to allow you to give bias to the original data points. Take a look at
the page anyway if you're interested.

Rohan _e_ii

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"Rohan Bernett" <rox### [at] yahoocom> wrote in message
news:web.3d7d3ffedc16a7ab18ccf4f70@news.povray.org...
> Thorsten Froehlich wrote:
>
> >POV-Ray supports alpha channels in most image formats.  Please check the
> >documentation.
>
> I really meant loading the transparency map as a separate file.
>

That's possible too. Split the alpha channel out as a grayscale bitmap and use
it as the guiding image in an image_pattern statement.

--
light_source{0,1}#macro c(J,a)sphere{0,1pigment{rgb z}scale a translate J+O}
#end#macro B(R,V,O)c(0,4)intersection{c(V,R)difference{c(-z*4x+10)c(-z*4.1x+
10)c(0<7.5,45,5>)}}#end B(12,0z*25)B(8y*4<0,12,50>)          // Batronyx ^"^

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