# panotools to map textures, patterns etc?

Hi!

For me (as I am a student of architecture and not of mathematics) it's
very difficult to understand how to map onto non-planar objects. E.g. if
I want to map onto a cylinder, I know that there is a cal-file, but I
don't really understand this. Now, maybe I should try, but I just found
a set of tools called panotools (www.panotools.org), which is able to
convert bitmap-files from different projections. Would it be possible to
use it to create imagefiles that could be mapped onto e.g. a radiance
cylinder without any further calculations, just like mapping iot onto a
plane? I would really like to have pic-files that don't need any further
calculations.

So, maybe someone tried something like this before? Or am I completely
wrong with this?

Thank You, CU, Lars.

"Lars O. Grobe" wrote:

Hi!

For me (as I am a student of architecture and not of mathematics) it's
very difficult to understand how to map onto non-planar objects. E.g. if
I want to map onto a cylinder, I know that there is a cal-file, but I
don't really understand this. Now, maybe I should try, but I just found
a set of tools called panotools (www.panotools.org), which is able to
convert bitmap-files from different projections. Would it be possible to
use it to create imagefiles that could be mapped onto e.g. a radiance
cylinder without any further calculations, just like mapping iot onto a
plane? I would really like to have pic-files that don't need any further
calculations.

So, maybe someone tried something like this before? Or am I completely
wrong with this?

Thank You, CU, Lars.
_______________________________________________

Hi Lars,

don't know panaotools, but wouldn't think its feasible. The mapping glues
world coordinates
(the xyz-coordinates your cylinder is defined in) to texture coordinates
(the pixel number in your image),
so it's somewhat 'outside' the image itself.

--math-on--

Peter Apian-Bennewitz wrote:

However, it's disappointing for casual users that Radiance
hasn't got default mappings for geometric
primitives (GUI builders- any comments ?).

Automatic mappings on single geometric primitives would be
relatively simple, but also not very useful. In most cases,
mappings will be applied to a group of primitives together,
eg. all the polygon segments of a curved wall. There's no
good way to automatically determine the axis of a cylindrical
mapping without user interaction in such a case.

I can only speak for myself, but enabling casual users to
place mappings without effort is not very high on my list of
priorities. Neither your example file nor the very similar
cyl.cal in the standard library require any deep mathematical
understanding. And of course, Lars isn't really a casual user,
(especially after buying a certain piece of software on Ebay)
so I'm sure he'll eventually figure them out...

-schorsch

···

--
Georg Mischler -- simulations developer -- schorsch at schorsch.com
+schorsch.com+ -- lighting design tools -- http://www.schorsch.com/

Hi!

Georg Mischler wrote:

Automatic mappings on single geometric primitives would be
relatively simple, but also not very useful. In most cases,
mappings will be applied to a group of primitives together,
eg. all the polygon segments of a curved wall. There's no
good way to automatically determine the axis of a cylindrical
mapping without user interaction in such a case.

Ok, I didn't want "automatic mapping" (something like this might be done
in the modeler, as I can find the axis of a cylinder quite easy there -
so this is what makes conrad interesting, as it exports 3ds-mappings).
What I think about is a way to create a static map for the object, so
that I can edit the mapping for this object until it fits and save this
pic-file. So I would not have the calculations in cal-files any more. Of
course this means a loss of flexibility, maybe it's simply better to
hold the complete object as an oct-file.

I can only speak for myself, but enabling casual users to
place mappings without effort is not very high on my list of
priorities.

Mappings are usually not the most important feature in radiance at all.

(especially after buying a certain piece of software on Ebay)

this "piece of software" is happily running on my laptop now!
There's just one reason for my question. I am working on a model of a
church. In fact, mappings are not the most important for our project,
but we have documented most important surfaces. So we have photos of the
domes, what AFAIK means a planar projection of a spherical surface. I
wonder how I would map this easily, if it gets important... ooops....
might it be that I could simply map it as on a planar surface in this
case...?

CU, Lars.

"Lars O. Grobe" wrote:

> I can only speak for myself, but enabling casual users to
> place mappings without effort is not very high on my list of
> priorities.

Mappings are usually not the most important feature in radiance at all.

I've found rshow's semi-automatic mapping for polygons quite useful in
projects, but

> (especially after buying a certain piece of software on Ebay)

this "piece of software" is happily running on my laptop now!

?

There's just one reason for my question. I am working on a model of a
church. In fact, mappings are not the most important for our project,
but we have documented most important surfaces. So we have photos of the
domes, what AFAIK means a planar projection of a spherical surface. I
wonder how I would map this easily, if it gets important... ooops....
might it be that I could simply map it as on a planar surface in this
case...?

Reproducing the 3d->2d transformation of the camera results in the image
being where it was (well, not actually very suprisingly).
For long focal length, a planar mapping approximates the perspective
transformation. That works whether the surface is
actually planar or spherical, as you guessed,

-Peter

···

--
pab-opto, Freiburg, Germany, www.pab-opto.de