In article <3eab03ee@news.povray.org> , Wolfgang Wieser <wwi### [at] gmxde>  
wrote:

> Either smart "intelligent" mixed-resolution meshes with (at least
> primitive) viewport culling or a very fine mesh is required.
> OR, subdivision at render time.
> Anything else?

Culling is of little use for ray-tracing, it is a typical scanline render
acceleration technique.

However, I recall a paper (in ACM TOG iirc) about an optimized level of
detail algorithm for terrain modeling that was suitable for ray-tracing.
And I am sure somebody has already invented a method for fitting huge meshes
such that they can be used by ray-tracing - RAM to store meshes of whole
planets has _not_ been affordable or available for a long time after all.
And the need to store those meshes has existed for a much longer time!

    Thorsten

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e-mail: tho### [at] trfde

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> Culling is of little use for ray-tracing, it is a typical scanline render
> acceleration technique.
> 
I was talking about culling as a technique to keep the mesh include file 
small. Because if you have a 100 million triangle mesh of a planet but 
only see 5% of them, you can try and do viewport culling -- otherwise 
the mesh will not fit into memory. 

>And I am sure somebody has already invented a method for fitting huge
>meshes such that they can be used by ray-tracing 
>
What about 1 byte per triangle? 

It only works for planets with 2 byte height info with the height 
info being the height difference to a sphere surface. 

If I have time, maybe I'll implement that. 

The general problem is that each vertex uses up at least 3*4 bytes. 
The only way I could imagine saving space is a better triangle-to-vertex 
mapping. 

Or, in-memory compression...

Yes, one could do in-memory compression when using a hierarchy. 
It will probably even be faster than using swap memory for the mesh. 

Wolfgang

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In article <3eabfca7@news.povray.org>, Wolfgang Wieser <wwi### [at] gmxde> 
wrote:

> > Culling is of little use for ray-tracing, it is a typical scanline render
> > acceleration technique.
> > 
> I was talking about culling as a technique to keep the mesh include file 
> small. Because if you have a 100 million triangle mesh of a planet but 
> only see 5% of them, you can try and do viewport culling -- otherwise 
> the mesh will not fit into memory. 

That's still holding 5 million triangles, and breaking things like 
reflections. You don't seem to get it...that is an example of setting up 
the scene wrong. You are using a much higher resolution mesh than you 
need.

-- 
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:

>> I was talking about culling as a technique to keep the mesh include file
>> small. Because if you have a 100 million triangle mesh of a planet but
>> only see 5% of them, you can try and do viewport culling -- otherwise
>> the mesh will not fit into memory.
> 
> That's still holding 5 million triangles, and breaking things like
> reflections. You don't seem to get it...that is an example of setting up
> the scene wrong. You are using a much higher resolution mesh than you
> need.
> 
Okay, then please give me your advice: How should I set up the scene 
correctly? I'll do just that and we'll see if it looks nice. 

I want to animate a space ship which flies to a planet, along a valley 
in the topography and back up into space. 

Wolfgang

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In article <3eac0502@news.povray.org>, Wolfgang Wieser <wwi### [at] gmxde> 
wrote:

> Okay, then please give me your advice: How should I set up the scene 
> correctly? I'll do just that and we'll see if it looks nice. 
> 
> I want to animate a space ship which flies to a planet, along a valley 
> in the topography and back up into space. 

A sphere primitive for the planet. As you get closer, a mesh of the area 
visible from the ship...a few hundred thousand triangles, maybe a 
million. Once you get close to the canyon, switch to a high level of 
detail mesh, the detail will probably require a million or so. Then back 
through a medium LOD mesh (maybe the same as the one on incoming, maybe 
different) and then switch to the sphere again. 2 or 3 meshes, none 
having anything near 100 million triangles. You could set things up so 
you have one bigger mesh with variable amounts of detail, highest in the 
canyon...simpler but less efficient, but nowhere near as bad as your 
idea of using a full-resolution mesh of an entire freaking planet. 
*That* is just wasteful on current systems, even if you have the RAM for 
it.

-- 
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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Wolfgang Wieser wrote:
> 
> [...]
> Okay, then please give me your advice: How should I set up the scene
> correctly? I'll do just that and we'll see if it looks nice.
> 
> I want to animate a space ship which flies to a planet, along a valley
> in the topography and back up into space.

I recently showed some samples of high detail rendering of the earth with
variable level of detail.  See:

Subject: rendering the earth (71k+68k)
Date: Tue, 01 Apr 2003 22:57:55 +0200
From: Christoph Hormann <chr### [at] gmxde>
Newsgroups: povray.binaries.images

The data the renders are based on would result in ~3.5 billion triangles
when rendered as a whole with a mesh.  

You can apply the same method (i.e. rendering a planetary body with an
isosurface defined by image maps, using higher resolution data for the
foreground part and blending with the lower resolution basis using
functions) to any other planet.

Christoph

-- 
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Christopher James Huff wrote:

> none having anything near 100 million triangles. You could set things up so
> you have one bigger mesh with variable amounts of detail, highest in the
> canyon...simpler but less efficient, but nowhere near as bad as your
> idea of using a full-resolution mesh of an entire freaking planet.
> *That* is just wasteful on current systems, even if you have the RAM for
> it.

I'm rendering a scene right now that has over 130 million triangles and
the parse time for just the mesh include files is about 8 minutes on my
1 ghz machine. Add in texture computations, radiosity, area lighting,
the trace function and few other things, the total parse time is around
12 min. I would hate to do that for every frame of an animation...!

-- 
Ken Tyler

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In article <3eabfca7@news.povray.org> , Wolfgang Wieser <wwi### [at] gmxde>  
wrote:

> What about 1 byte per triangle?
>
> It only works for planets with 2 byte height info with the height
> info being the height difference to a sphere surface.

Why do you use a mesh if you want a height field???  You can already do what
you suggest easily with POV-Ray 3.5 using an isosurface and an image map
pattern!

    Thorsten

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

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

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Wolfgang Wieser <wwi### [at] gmxde> wrote:
> I was talking about culling as a technique to keep the mesh include file 
> small. Because if you have a 100 million triangle mesh of a planet but 
> only see 5% of them, you can try and do viewport culling -- otherwise 
> the mesh will not fit into memory. 

  There's no way of knowing which parts of the mesh will not be visible
in the final image other than raytracing the image.
  Raytracing is more versatile than scanline-rendering: In scanline rendering
when a triangle is facing away or if it's located outside the viewing port,
you know that it will not be visible. However, raytracing is not that simple.
A triangle can be far behind the camera, yet be visible in the final image.


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[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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Ken wrote:

> I'm rendering a scene right now that has over 130 million triangles and
> the parse time for just the mesh include files is about 8 minutes on my
> 1 ghz machine. 
>
I cannot imagine that. 
I have to wait >4 minutes to get 1 million triangles parsed 
on a 1.4 GHz box. 

Furthermore, you must have more than 4Gb of virtual memory. 

Wolfgang

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