Nieminen Juha wrote:
> 
>   Wouldn't displacement mapping require LOTS of triangles? And I mean _LOTS_.
>   Just think that you want to apply a 640x480 displacement map to each side
> of a cube. If I have understood correctly, you will need at least 2 triangles
> per map pixel (like in a heightfield), which would make a total of at least
> 640x480x2x8 = 4915200 triangles.
>   Since this kind of triangle mesh can not (AFAIK) be optimized like a
> height field can be, it would take rather lot of memory.
> 
>   Perhaps I'm just exaggerating.

Since other programs offer this feature there must be some way to optimize
the process so it is not so memory and parsing intensive. There must be :)

-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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On 29 Feb 2000 08:24:35 -0500, Nieminen Juha wrote:
>  Wouldn't displacement mapping require LOTS of triangles? And I mean _LOTS_.
>  Just think that you want to apply a 640x480 displacement map to each side
>of a cube. If I have understood correctly, you will need at least 2 triangles
>per map pixel (like in a heightfield), which would make a total of at least
>640x480x2x8 = 4915200 triangles.
>  Since this kind of triangle mesh can not (AFAIK) be optimized like a
>height field can be, it would take rather lot of memory.
>
>  Perhaps I'm just exaggerating.

There are ways to make it less memory-intensive.  One is to displacement-map 
adaptively.  This is particularly useful if you have information on the 
footprint of the ray, but if you're not careful it can lead to cracking.  
Another is to displacement-map on demand and cache the results, but 
raytracing can be markedly less coherent than other rendering methods, so a 
cache might not be as good a solution in a raytracer.  There have been a 
number of papers written on the subject.

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

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Chris Huff wrote:
> 
> In article <38B7FCCF.A533B213@merlin.net.au>, PoD <pod### [at] merlinnetau>
> wrote:
> 
> > I didn't mean not to include the z-depth option, just that using planar
> > mapping would make a lot of uses difficult.  Maybe reuse the mapping
> > keyword here, I could see at least spherical, planar and cylindrical
> > being useful.
> 
> Not planar mapping, spherical mapping. Distance would be z, and
> vertical/horizontal angle would be x and y, and the center would be the
> light_source position. It would be like wrapping the pigment around the

Sorry, I read x and y and assumed planar mapping.

> sphere, except the color also varies depending on it's distance from the
> center of the sphere. You would have to tile it in some cases(many times
> the tiling wouldn't be visible), but I don't see any other way of
> mapping 3D space around a point. Maybe also cylinderical mapping.

Planar would be useful for image mapped lights such as slide projectors.

> 
> > Here's something if you had z-depth.  Use a density file as the pattern
> > and project 'solid' holograms into media with shadowing from intervening
> > objects :)
> 
> That is an idea...although I guess it could also be done with scattering
> media using the density file and a plain colored light, at least as long
> as no other lights interact with it.

That's pretty much what I'd do with current POV, but it'd look pretty
cool in an animation with characters walking in front of the projector.

PoD.

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ron### [at] povrayorg (Ron Parker) writes:

> On Tue, 29 Feb 2000 05:06:01 -0800, Ken wrote:
> >
> >
> >Peter Popov wrote:
> >> 
> >> With time I've compiled a list of features I would be happy to see in
> >> POV-Ray. I think it wouldn't hurt if I posted it here.
> >
> >Here is my little wish list - tee hee !
> >
> >1.) displacement mapping
> >
> >2.) export capabilities pov2???
> >
> >3.) programmable shaders ala renderman
> >
> >4.) the ability to internaly tesselate POV-Ray primatives
> >
> >5.) subdivision surfaces
> >
> >6.) extended capabilities for the warp turbulence feature
> >
> >7.) nurbs
> 
> Most of these are perfectly reasonable things to wish for.  (1) and (2) are 
> of course rather dependent on (4), and of course that ability would be 
> limited to the primitives that can be tesselated.

Mmmh, wouldn't it be possible to calculate displacement mappings on the
fly. I mean -- we have isosurface functions now. Something like this:

#version unofficial MegaPov 0.4;
camera { location<15,40,-35>  direction<0,0,5.5> look_at<0,0,0>}

light_source {<-50, 40, -20> color <1,1,1>}
light_source {<  0, 50, -50> color <1,1,1>}
background {color <0.65,0.72,0.72>}

#declare P0=0.2;
#declare P1=0.2;
#declare BOX = function { ( abs(x)^(2/P0) + abs(y)^(2/P0) ) ^ (P0/P1)
  + abs(z)^(2/P1) - 1}

#declare RUSTY_BOX =
    function{ BOX(x,y,z) + 0.2*noise3d(40*x,40*y,40*z) }

isosurface {
  function { RUSTY_BOX }
  contained_by{ box {<-1.1, -1.1, -1.1>, <1.1, 1.1, 1.1>}} 
  eval
  threshold  0.18
  method 2
  pigment {colour <0.65,0.3,0.1>}
  finish {ambient 0.3}
  scale 3
}

Of course, some work has to be done to apply this technique to other
primitives and composed objects.

Thomas

-- 
http://thomas.willhalm.de/ (includes pgp key)

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"Thorsten Froehlich" <tho### [at] trfde> writes:

> In article <qqmd7phhh09.fsf_-_@schlatt.fmi.uni-konstanz.de> , Thomas 
> Willhalm <tho### [at] willhalmde>  wrote:
> 
> > It appears to me, that the time for the complete rewrite in C++
> > (i.e. POV-Ray 4.0) has come. Does somebody know, whether the
> > POV-Team has already started? (I'm looking forward to discuss
> > design and implementation issues.)
> 
> povray.announce.frequently-asked-questions:  "POV-Ray plans for v3.1 and
> beyond..."

I was aware of this article, but it is more than one year old. Furthermore,
it contains the sentence:

"We hope to be able to do some of that work [on POV-Ray 4.0] in parallel
with our work on 3.5 but that may be wishful thinking."

That's why I asked about the current state of POV-Ray 4.0. From your
comment I conclude that Chris' wish hasn't been fulfilled.

Thomas

-- 
http://thomas.willhalm.de/ (includes pgp key)

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Thomas Willhalm wrote:

> I was aware of this article, but it is more than one year old. Furthermore,
> it contains the sentence:
> 
> "We hope to be able to do some of that work [on POV-Ray 4.0] in parallel
> with our work on 3.5 but that may be wishful thinking."
> 
> That's why I asked about the current state of POV-Ray 4.0. From your
> comment I conclude that Chris' wish hasn't been fulfilled.

Let's suffice it to say that the POV-Team is not willing to discuss
specific plans for POV-Ray v4.0 at this time and leave it at that.

-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Ken <tyl### [at] pacbellnet> writes:

> Thomas Willhalm wrote:
> 
> > I was aware of this article, but it is more than one year old. Furthermore,
> > it contains the sentence:
> > 
> > "We hope to be able to do some of that work [on POV-Ray 4.0] in parallel
> > with our work on 3.5 but that may be wishful thinking."
> > 
> > That's why I asked about the current state of POV-Ray 4.0. From your
> > comment I conclude that Chris' wish hasn't been fulfilled.
> 
> Let's suffice it to say that the POV-Team is not willing to discuss
> specific plans for POV-Ray v4.0 at this time and leave it at that.

If so, it's a pity that I cannot throw in my knowledge about expression
templates and design patterns. But perhaps they already know about all
this stuff...

Thomas

-- 
http://thomas.willhalm.de/ (includes pgp key)

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Thomas Willhalm wrote:

> If so, it's a pity that I cannot throw in my knowledge about expression
> templates and design patterns. But perhaps they already know about all
> this stuff...

It is not really so much that they are unwilling to discuss this with
you it's just that your timing is not good. POV-Ray v3.5 isn't even
out the door yet and there is still work to be done on it before it
is ready. Any discussions you may wish to hold now would not be timely
and would only distract them from what they are working on now.

Thorsten's somewhat cryptic reply was his attempt to let you know that
they do not want to discuss it now.

-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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In article <38BBF253.DD031485@pacbell.net> , Ken <tyl### [at] pacbellnet>  
wrote:

> It is not really so much that they are unwilling to discuss this with
> you it's just that your timing is not good. POV-Ray v3.5 isn't even
> out the door yet and there is still work to be done on it before it
> is ready. Any discussions you may wish to hold now would not be timely
> and would only distract them from what they are working on now.
>
> Thorsten's somewhat cryptic reply was his attempt to let you know that
> they do not want to discuss it now.

Exactly.  I wish I could write as short and still understandable in English
as Ken does...


      Thorsten


PS: Ken, are you for hire as a ghostwriter?


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

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

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Thorsten Froehlich wrote:

> Exactly.  I wish I could write as short and still understandable in English
> as Ken does...

A practiced art...

> PS: Ken, are you for hire as a ghostwriter?

Perhaps as long as you don't need long winded political speeches :)

-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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