In article <3ee6c543@news.povray.org> , gk <g_k### [at] mail333com>  wrote:

>Date: Wed, 11 Jun 2003 12:59:06 -0600
>From: gk <g_k### [at] mail333com>

Hi,

Please correct your system clock and/or timezone.  It is ahead of the rest
of the world.

    Thorsten

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Lutz-Peter Hooge wrote:
> 1) It is enabled with "interpolation 3"
> In image.h this is/was mapped to CUBIC_SPLINE, but wasn't implemented
>
What about introducing string names as alternatives to the numeric 
values? Then one could prevent ambiguities and make the scene file more 
readable. The numeric values can still be accepted, too. 

Wolfgang

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ABX <abx### [at] abxartpl> wrote:
> Isn't this already available in
> http://staff.aist.go.jp/r-suzuki/e/povray/iso/df_body.htm

  No, that's df3 interpolation. I talk about image map interpolation.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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>  Mipmapping is a technique to avoid these moire artifacts.

NO NO NO! Not mip mapping in POVRay! Mip mapping ruins the image. Whenever I
play any of the Quake-based games, I turn it off. I think things look a lot
better without it. I'd rather have the shimmering, than the blurriness.

Now, how about including Trilinear/Tricubic interpolation for use with voxel
objects?

Rohan _e_ii

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Christopher James Huff <cja### [at] earthlinknet> wrote:

> But a direct implementation would be faster, right?

Of course.

> > But I think it is also possible to modify the matrix to get a sharper
> > image (with the tradeoff of getting more grid artifacts)

I experimented a bit with it. At least blur and sharpen is possible.

Lutz-Peter

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Rohan Bernett <rox### [at] yahoocom> wrote:
> NO NO NO! Not mip mapping in POVRay! Mip mapping ruins the image.

  Strange claim.
  Trilinear filtering is closer to the photographic phenomenon than the
plain bilinear filtering. In other words, it's more photorealistic.

  In the real world, when you scan a photograph (or take a photo with a
high-quality digital camera), one pixel will be the average of all the
colors inside the pyramid which goes through that pixel towards the scene.
This is exactly what trilinear filtering simulates: It averages all the
texture pixels which fall into this pyramid to get the pixel color.
  That is, if 40 of the texture pixels are inside that singe image pixel,
the average of all those 40 pixels is calculated there (as would happen
with a photograph).

  In regular bilinear filtering this does not happen. Instead of taking
into account all the 40 texture pixels, it takes 4. All the other 36
texture pixels are simply ignored.
  You can imagine that if the texture has very fine details, this causes
really bad moire effects.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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In article <3ee7479b$1@news.povray.org>,
 Lutz-Peter Hooge <lpv### [at] gmxde> wrote:

> I don't think so. It would be correct for a reflection on a plane, but 
> totally wrong for a reflection on a small sphere.
> To make it correct the 'width' of the ray would be needed, and to 
> calculate (an approximation of) this, the curvature of the reflective/
> refractive surface at the intersection point would be needed.

You need to track the ray footprint, it's called differential ray 
tracing. If I remember right, Ron Parker was talking about this a few 
years ago, but never got it added to POV.

http://graphics.stanford.edu/papers/trd/

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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In article <web.3ee7f5f8d02fbf4518ccf4f70@news.povray.org>,
 "Rohan Bernett" <rox### [at] yahoocom> wrote:

> >  Mipmapping is a technique to avoid these moire artifacts.
> 
> NO NO NO! Not mip mapping in POVRay! Mip mapping ruins the image. Whenever I
> play any of the Quake-based games, I turn it off. I think things look a lot
> better without it. I'd rather have the shimmering, than the blurriness.

Mip-mapping is simply a way to more cheaply do supersampling. Small 
details can not be represented by the pixels, so the details in each 
pixel are blended together. The final image has more information, not 
less, and is a more realistic representation of what the eye or a camera 
would see. You might as well be ranting against the use of antialiasing.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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Christopher James Huff wrote:

> Mip-mapping is simply a way to more cheaply do supersampling. Small
> details can not be represented by the pixels, so the details in each
> pixel are blended together. The final image has more information, not
> less, and is a more realistic representation of what the eye or a camera
> would see. You might as well be ranting against the use of antialiasing.

Both AA and MM have their advantages and drawbacks. Many a time I have
lamented the severe AA settings I had to use to get rid of strait edge
stair stepping only to see my textures and other geometry related details
suffer as a result.

-- 
Ken Tyler

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>Both AA and MM have their advantages and drawbacks. Many a time I have
>lamented the severe AA settings I had to use to get rid of strait edge
>stair stepping only to see my textures and other geometry related details
>suffer as a result.

Hear Hear!

Rohan _e_ii

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