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Christoph Hormann <chr### [at] gmx de> wrote:
> - normal perspective camera
Why would the camera type make trilinear interpolation difficult?
The program would just have to estimate the distance between pixels
projected on the surface of the object.
Besides, I think that people would find it useful even if it would
be limited to the perspective camera. 99.9% of the images rendered
with povray use the perspective camera.
> - No warps etc. being applied to the image map.
Even if trilinear interpolation was limited to triangle meshes without
texture modifiers I still think people would find it useful.
> To sum it up - in all cases where you probably are faster using hardware
> accelerated scanline rendering anyway.
I don't think speed is the issue here. The issue is that you can't
achieve trilinear interpolation of image maps with povray at all.
Besides, how would you render povray scenes with hardware acceleration?
> Again - if you implement something along these lines that is surely
> interesting from the technical standpoint but the practical use will be
> very limited.
Somehow people using scanline renderers manage to survive with
using only triangle meshes and image maps. Even if POV-Ray only
supported as much as scanline renderers it would be exactly as useful.
It's not at all asimilar to uv-mapping.
--
- Warp
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I am not interested in theoretically discussing this - if you like to
implement this either by reducing POV-Ray to the features of a scanline
renderer or by applying estimations everywhere do so and show the
results but don't try to argument on a theoretical basis how useful this
would be and that it won't cause problems anywhere.
Christoph
--
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 03 May. 2005 _____./\/^>_*_<^\/\.______
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tahoma wrote:
>> In the end i doubt this will lead to better results in shorter time
>> (but i will be happy to be proven wrong).
>
> That's why mipmapping or trilinear filtering is common practice in realtime
> graphics.
Do you think the reason for why it is commonly used is that it won't
lead to better results in shorter time or that i will be proven wrong?
And it is not 'mipmapping or trilinear filtering' - mip-mapping can be
used with trilinear filtering or with other filtering techniques.
> Beside the fact that is decreases cache misses for gpu's to fetch
> texels it gives better results without FSAA.
> Nevertheless you can do fancy things with different textures. If you
> don't use
> just downsampled textures you can achieve some nice texturing effect
> depended
> on the fragment distance. I don't know if there exists a pattern in
> povray for
> this.
The distance of the surface from the camera is only one out of many
factors that influence the size an image map appears in in POV-Ray. You
will only be able to estimate the size and this will only be accurate if
you add some rather expensive calculations (like tracing additional rays).
Christoph
--
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 03 May. 2005 _____./\/^>_*_<^\/\.______
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Christoph Hormann <chr### [at] gmxde> wrote:
> I am not interested in theoretically discussing this - if you like to
> implement this either by reducing POV-Ray to the features of a scanline
> renderer or by applying estimations everywhere do so and show the
> results but don't try to argument on a theoretical basis how useful this
> would be and that it won't cause problems anywhere.
I don't understand your attitude. First you are extremely rude and
impolite to the original poster, who made a perfectly valid and legit
question and now you are nitpicking about the "usefulness" of a limited
trilinear interpolation which is rather odd given that there's at least
one other scanline-rendering feature in povray which is equally limited,
namely uv-mapping, and you are not complaining about its "usefulness".
Why is trilinear interpolation so much different from uv-mapping
(in the context of limitations and how useful it can be)?
--
- Warp
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Warp wrote:
>
> I don't understand your attitude. First you are extremely rude and
> impolite to the original poster, who made a perfectly valid and legit
> question
The original statement i replied to was:
"Is there a way to specify mipmaps in povray or can povray do it by
itself? The only interpolation schemes i found are 'bilinear' and
'normalized distance'."
And if you think this is a perfectly valid and legit question i can only
note we have a different view here.
The correct way to ask the question Tim gave the answer for would have
been "rendering a scene with image maps gives unexpectedly bad results
for me - what can be done about this?". Instead wrong assumptions were
made how the solution for the problem should look like. My reply was
clearly referring to the way the question was asked and not personally
rude against the poster.
Note for a moment i considered an ironic reply - that next MegaPOV will
support bicubic interpolation for image maps - but i refrained from
doing so since it would have most likely been misunderstood.
> and now you are nitpicking about the "usefulness" of a limited
> trilinear interpolation which is rather odd given that there's at least
> one other scanline-rendering feature in povray which is equally limited,
> namely uv-mapping, and you are not complaining about its "usefulness".
I don't see anything that relates uv-mapping to scanline rendering
except that uv-mapping is very common for meshes and meshes are at the
same time the only geometry you can render with a scanline renderer.
The only thing that is required to use uv-mapping in POV-Ray is a shape
that defines uv-coordinates which has nothing to do with scanline
rendering either. It would not even need to be possible to describe the
surface parametrically - you could even uv-map an isosurface (although
this would be rather pointless).
I really don't understand why you want to force a controversy here. I
did not reject an implementation of the feature you are proposing nor
did i say it won't be added to official POV-Ray when you implement it.
I just stated by doubts about it.
Christoph
--
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 03 May. 2005 _____./\/^>_*_<^\/\.______
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> "Is there a way to specify mipmaps in povray or can povray do it by
> itself? The only interpolation schemes i found are 'bilinear' and
> 'normalized distance'."
>
> And if you think this is a perfectly valid and legit question i can only
> note we have a different view here.
>
> The correct way to ask the question Tim gave the answer for would have
> been "rendering a scene with image maps gives unexpectedly bad results
> for me - what can be done about this?". Instead wrong assumptions were
> made how the solution for the problem should look like.
It is not possible to formulate a question regarding to the answer. Thats
paradox. As i said, i did not want to tell anyone, how the solution should
look like. I wanted to know whether povray support a technique or not. My
experiences (in realtime graphics) showed that trilinear filtering
improves the image quality with respect to rendering speed more that FSAA.
Maybe it was dumb or even respectless to the povray community to ask such
question, but it came to quite a huge discussion about mipmapping and
derived image filter techniques. Maybe you should listen to others and
merge their ideas with yours instead of just saying: no. When time comes
you will be lucky that someone will listen to you.
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tahoma wrote:
>
> It is not possible to formulate a question regarding to the answer. Thats
> paradox. As i said, i did not want to tell anyone, how the solution should
> look like. I wanted to know whether povray support a technique or not.
But you said "When using image_maps i could not manage to get really
nice visual results because of high sampling frequencies."
And this led Tim to mention antialiasing. Was his reply useful to
achieve 'nice visual results'? Would it have helped you more to get a
simple 'No' as the answer?
> Maybe it was dumb or even respectless to the povray community to ask such
> question,
If the purpose of your question was to solve an actual problem in using
POV-Ray (namely to get visually pleasing results) - which usually can be
assumed of a posting in this newsgroup - your question was not
formulated well. This is what i tried to point out in my original reply.
Christoph
--
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 03 May. 2005 _____./\/^>_*_<^\/\.______
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Christoph Hormann <chr### [at] gmxde> wrote:
> The original statement i replied to was:
> "Is there a way to specify mipmaps in povray or can povray do it by
> itself? The only interpolation schemes i found are 'bilinear' and
> 'normalized distance'."
> And if you think this is a perfectly valid and legit question i can only
> note we have a different view here.
That question is basically the same thing as "does povray support
mipmapping?". What's so terribly wrong about that question that it deserves
such a heated reply as yours?
> The correct way to ask the question Tim gave the answer for would have
> been "rendering a scene with image maps gives unexpectedly bad results
> for me - what can be done about this?". Instead wrong assumptions were
> made how the solution for the problem should look like. My reply was
> clearly referring to the way the question was asked and not personally
> rude against the poster.
I think it was. You told him directly that he doesn't know what he is
talking about and that he should study some raytracing theory before
asking stupid questions.
Perhaps you didn't *intend* it to be rude, but it was nevertheless.
> > and now you are nitpicking about the "usefulness" of a limited
> > trilinear interpolation which is rather odd given that there's at least
> > one other scanline-rendering feature in povray which is equally limited,
> > namely uv-mapping, and you are not complaining about its "usefulness".
> I don't see anything that relates uv-mapping to scanline rendering
You are concentrating way too much on one term in my text which was
in no way the point I wanted to express. Add the word "typical" before
"scanline-rendering" if you want.
My point was not about whether uv-mapping is a scanline-rendering
technique or not, but that uv-mapping is similar to the would-be
trilinear interpolation in that it would be possibly limited to
only certain objects or whatever. However, no-one is complaining about
the limitations of uv-mapping; thus why would limitations in
trilinear interpolation be any different? You are talking as if it
would be useless if it can't be used *everywhere* in all cases.
> I really don't understand why you want to force a controversy here.
The controversy is that you quite clearly expressed that implementing
a trilinear interpolation of image maps which would work everywhere is
too difficult to be feasible and that a trilinear interpolation which
is limited to only certain cases would be mostly useless.
I disagree with the latter opinion.
--
- Warp
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>> It is not possible to formulate a question regarding to the answer.
>> Thats
>> paradox. As i said, i did not want to tell anyone, how the solution
>> should
>> look like. I wanted to know whether povray support a technique or not.
>
> But you said "When using image_maps i could not manage to get really
> nice visual results because of high sampling frequencies."
>
> And this led Tim to mention antialiasing. Was his reply useful to
> achieve 'nice visual results'? Would it have helped you more to get a
> simple 'No' as the answer?
I presented my problem. I had a solution in my mind, but couldn't
find a way to do it with povray. So i was asking for that way.
The reason for posting the problem is to get other optinion about
reaching the goal.
Tim's answer was very helpful, yours wasn't. After reading your post
i was none the wiser.
>> Maybe it was dumb or even respectless to the povray community to ask
>> such
>> question,
>
> If the purpose of your question was to solve an actual problem in using
> POV-Ray (namely to get visually pleasing results) - which usually can be
> assumed of a posting in this newsgroup - your question was not
> formulated well. This is what i tried to point out in my original reply.
You said: "Sorry but the fact you write this shows that you have
absolutely no idea how
raytracing works and what mip-mapping is. I don't want to appear brusk but
you should
think about things and inform yourself a bit better before posting
something like this."
If that means, my question was not well formulated, i still have to learn
a lot :)
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"Christoph Hormann" <chr### [at] gmxde> wrote in message
news:d5vd6f$p2c$1@chho.imagico.de...
> Warp wrote:
> >
> > I don't understand your attitude. First you are extremely rude and
> > impolite to the original poster, who made a perfectly valid and legit
> > question
>
> The original statement i replied to was:
>
> "Is there a way to specify mipmaps in povray or can povray do it by
> itself? The only interpolation schemes i found are 'bilinear' and
> 'normalized distance'."
>
> And if you think this is a perfectly valid and legit question i can only
> note we have a different view here.
>
i just want to say that this is the newusers group. there is almost no
invalid question here as far as i'm concerned, if the topic is somehow
povray related.
-r
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