"Thomas de Groot" <t.d### [at] internlDOTnet> wrote:
> I have returned to last year's 'Eavesdropping', with the new figures I have
> been working on for the last couple of months. This is a fast,
> non-radiosity, render.
>
> The title could now be: "Iskander learns something to his advantage".
>
> Besides Iskander, the other figures are the Rais Abdul ibn Abdullah (of
> course), and a newcomer: captain Adamastor. The place is the city of
> Gancaloon, gate to the world of dreams.
>
> Thomas

Oh, that's a very nice image! Congratulations!
I don't know if there's something wrong with my screen, but the shadow of
the column falling in the middle of the screen has strange fuzzy edges as
if it were painted with an irregural brush in a 2d program (which I don't
doubt for a second that it isn't ;-) ).
The ropes are great, and I can't imagine a pier without them, but the ropes
seemingly dangling from the columns strike me as peculiar.

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Thomas de Groot wrote:
> I fully agree. A distinction should be made indeed and these kind of 
> images/scenes, in my view, are not intended to be hanging on a wall.

I hope you didn't miss my point that I believe this scene to be an
exception to that rule - perhaps because it's not as full a scene as it
appears to be. The focus of the image is narrow and obvious. The simple
surroundings frame rather than distract from the subject. Realist
stylizations don't allow for much editorialization, but I think you've
used what tools are available within that stylization very effectively.

 -Shay

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Hey Thomas, it has come about that I am trying to model fluted columns. 
  Forgive me if you have talked about it before, but I am wondering how 
you are modeling your columns?

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"Shay" <shay@s.s> schreef in bericht news:46bda93a$1@news.povray.org...
> Thomas de Groot wrote:
>> I fully agree. A distinction should be made indeed and these kind of
>> images/scenes, in my view, are not intended to be hanging on a wall.
>
> I hope you didn't miss my point that I believe this scene to be an
> exception to that rule - perhaps because it's not as full a scene as it
> appears to be. The focus of the image is narrow and obvious. The simple
> surroundings frame rather than distract from the subject. Realist
> stylizations don't allow for much editorialization, but I think you've
> used what tools are available within that stylization very effectively.
>

No, no! I got your point, Shay, and thanks indeed for it. It is what I want 
to achieve, beyond the strictly anecdotal. Still, I have to say that it is a 
difficult balancing act. In a sense, I want the beholder to become an 
accomplice in the scene he/she is watching, turning him/her into a peeping 
tom as it were.
I want to add one more element to this scene and I am aware that it may 
destroy the effect, making it too explicit. If that is so, I shall leave it 
out.

Thomas

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"Grassblade" <nomail@nomail> schreef in bericht 
news:web.46bd944716060248364ceeb90@news.povray.org...
> Oh, that's a very nice image! Congratulations!
Thank you!

> I don't know if there's something wrong with my screen, but the shadow of
> the column falling in the middle of the screen has strange fuzzy edges as
> if it were painted with an irregural brush in a 2d program (which I don't
> doubt for a second that it isn't ;-) ).

What you see is the area_light effect. I may squeeze it a bit more indeed...

> The ropes are great, and I can't imagine a pier without them, but the 
> ropes
> seemingly dangling from the columns strike me as peculiar.

Well, I can only say that this is a peculiar place. ;-)
As far as I know, it is an ancient temple turned into a storehouse because 
of its convenient location alongside the harbour. So, all kinds of pullies 
and ropes have been attached to the ceiling etc...

Thomas

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"Jim Charter" <jrc### [at] msncom> schreef in bericht 
news:46bdd4f2$1@news.povray.org...
>
> Hey Thomas, it has come about that I am trying to model fluted columns.
>  Forgive me if you have talked about it before, but I am wondering how
> you are modeling your columns?

It has been a couple of years since I modelled these, so let me ponder...
(The first version I made in Wings3D, before switching everything over to 
Silo)

I followed the Greek guideline that says that a column, to be appealing to 
the eye, should not be a simple cone shape but bulge a tiny bit out at the 
middle. I acchieved this by using a vertically very elongated sphere, cut at 
the middle (i.e. the base of the column) and at the place where the top 
should be. You have to experiment with the vertical elongation until you 
have both bottom and top diameters correctly. An easy way to do this is to 
first make a proxy model in Moray to get the measurements needed.

Once the shaft of the column is thus obtained, I used (again) vertically 
very elongated toruses so that the curvature matched the curvature of the 
shaft. Again, a proxy in Moray can help but is not strictly necessary. The 
toruses have to be cut to the correct length of the flutes, provided with a 
top end (a sphere) and a bottom end (an inclined section). Then, by boolean 
substraction from the shaft, the flutes are successively modelled into the 
column shaft.

If you want to follow the classical rules, number and form of the flutes are 
fixed, but that is another discussion entirely.

Once you have the shaft modelled to your satisfaction, you can model 
separately the different elements that form the base of the column, and the 
top. The top part is particularly challenging because of the distinctive 
capitals. I have not attempted the Corynthian order!! The Ionian order is 
already difficult enough. I used a background image as a proxy for modelling 
that particular spiral shape.

I won't speak now about corner columns!!! They have their own challenges in 
the way to model the capitals.

The result is shown in this low resolution image when I finished building 
the complete temple.

Any doubts or questions? Just ask  :-)

Thomas

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Attachments:
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Preview of image 'ApolloTemple_11.jpg'

Thomas de Groot wrote:

> 
> I followed the Greek guideline that says that a column, to be appealing to 
> the eye, should not be a simple cone shape but bulge a tiny bit out at the 
> middle. I acchieved this by using a vertically very elongated sphere, cut at 
> the middle (i.e. the base of the column) and at the place where the top 
> should be. You have to experiment with the vertical elongation until you 
> have both bottom and top diameters correctly. An easy way to do this is to 
> first make a proxy model in Moray to get the measurements needed.

Yes, my approach too.  I saw somewhere on the web that Roman columns 
have more of a middle bulge but Greek have a curved taper but the base 
is the thickest.  No idea if they knew what they were talking about.
http://www.uen.org/Centennial/08BuildingsA.html



> 
> Once the shaft of the column is thus obtained, I used (again) vertically 
> very elongated toruses so that the curvature matched the curvature of the 
> shaft. Again, a proxy in Moray can help but is not strictly necessary. The 
> toruses have to be cut to the correct length of the flutes, provided with a 
> top end (a sphere) and a bottom end (an inclined section). Then, by boolean 
> substraction from the shaft, the flutes are successively modelled into the 
> column shaft.

Interestting.  So even though you are using mesh you used boolean 
subtraction of torii?  Again I have been trying exactly the same 
approach but with POV CSG.  The problem I had was getting the 
circumference of the torus to decrease at an rate appropriate to the 
diminishing circumference of the tapering shaft.

The other problem was how to position the spheres to difference out at 
the top of the flutes.  The solution I thought for the second issue was 
to begin with a sphere of radius square root two.  Then if I made the 
cap of the column at height one unit before scaling, the radius there 
would always be one unit no matter how I scaled it vertically, and using 
the supposed Greek model, the bottom radius would remain root two. So 
differencing spheres at both the top and bottoms of the column would be 
a known quantity.  (Actually with a little more calculation a narrower 
base could also be scaled down in the negative direction and have the 
radius remain known)

But what screwed this method up was the fact that the vertically scaled 
torii do not have a diminishing footprint on the diminishing 
circumference of the shaft.  By overscaling by 5/4 vertically, (ie if I 
wanted the top of the shaft to be at 20 units, I would scale the sphere 
and torii by 25 times vertically), I managed to get the relationship 
between the torii and the shaft circumference to look okay to the eye, 
at least, though the flutes are still narrower at the base than at the 
top.  But as soon as I did that I lost my ability to exactly position 
the spheres at the top.  If there is a mathematical relationship 
describing what the radius would be at the 4/5 point I couldn't find it. 
  I finally managed an 'eyeballed' solution for positioning the spheres 
but this feels as unsatisfying in so far as I doubt it would hold up for 
different ratios of height to radius.

The obvious advantage of mesh it is that the polys match the contour of 
the surface so that a vertical line of polys could be used to shape a 
flute which would diminish in size appropriately. So now I an curious as 
to why you used the boolean approach.


> 
> If you want to follow the classical rules, number and form of the flutes are 
> fixed, but that is another discussion entirely.

I would be intereseted if you have any references.  Right now I am using 
18 flutes, so a 20 degree rotation.


> 
> Once you have the shaft modelled to your satisfaction, you can model 
> separately the different elements that form the base of the column, and the 
> top. The top part is particularly challenging because of the distinctive 
> capitals. I have not attempted the Corynthian order!! The Ionian order is 
> already difficult enough. I used a background image as a proxy for modelling 
> that particular spiral shape.

Yeah, I'll give that a wait.  Actually for my purposes I can diverge 
from the strictly classical and indulge myself with my own caprices as 
well as any 19th century neoclassical architect


> 
> I won't speak now about corner columns!!! They have their own challenges in 
> the way to model the capitals.

Hasn't come since it is a circular collonade but will remember that when 
tempted to do the other.

> 
> The result is shown in this low resolution image when I finished building 
> the complete temple.

Very nice.  I am also impresses with the texture in 'Eavesdropping', 
which, if you are using mesh, must be a perturbed normal?

-Jim

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"Jim Charter" <jrc### [at] msncom> schreef in bericht 
news:46bf60d1$1@news.povray.org...
[...]
> The obvious advantage of mesh it is that the polys match the contour of 
> the surface so that a vertical line of polys could be used to shape a 
> flute which would diminish in size appropriately. So now I an curious as 
> to why you used the boolean approach.
>
I woke up this night with the sudden thought that I only used the boolean 
approach with the Moray proxy. I remember now (It has been about 4 years ago 
and I should have taken notes) that I modelled the flutes by moving the 
appropriate faces inwards from the surface of the mesh shaft and 
handcrafting the top and bottom. As you say, there are serious problems with 
the boolean approach where the size of the flutes is concerned.
I think now that an easier workflow would be to slice a pie section from a 
featureless shaft, exactly covering one flute width and twice the half rib 
widths; to craft the flute and finally to apply a rotational sweep to 
restore the complete shaft.

>
>>
>> If you want to follow the classical rules, number and form of the flutes 
>> are fixed, but that is another discussion entirely.
>
> I would be intereseted if you have any references.  Right now I am using 
> 18 flutes, so a 20 degree rotation.
24 seems to have been the general use in antiquity, at least in the 
classical period. However, older columns could have up to 48 flutes. Ribs 
were sharp during the Doric Order period, but flat (with deeper flutes) 
later.
>
>
>>
>> Once you have the shaft modelled to your satisfaction, you can model 
>> separately the different elements that form the base of the column, and 
>> the top. The top part is particularly challenging because of the 
>> distinctive capitals. I have not attempted the Corynthian order!! The 
>> Ionian order is already difficult enough. I used a background image as a 
>> proxy for modelling that particular spiral shape.
>
> Yeah, I'll give that a wait.  Actually for my purposes I can diverge from 
> the strictly classical and indulge myself with my own caprices as well as 
> any 19th century neoclassical architect
Great! :-)
That makes it a bit easier. My (calculated) handicap was that I wanted to 
reconstruct the real thing. I had to make concessions of course.

>
>>
>> I won't speak now about corner columns!!! They have their own challenges 
>> in the way to model the capitals.
>
> Hasn't come since it is a circular collonade but will remember that when 
> tempted to do the other.
No problem then indeed.

>>
>> The result is shown in this low resolution image when I finished building 
>> the complete temple.
>
> Very nice.  I am also impresses with the texture in 'Eavesdropping', 
> which, if you are using mesh, must be a perturbed normal?
Yes, that is right.

Thomas

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"Jim Charter" <jrc### [at] msncom> schreef in bericht 
news:46bf60d1$1@news.povray.org...
> Thomas de Groot wrote:
>
>>
>> I followed the Greek guideline that says that a column, to be appealing 
>> to the eye, should not be a simple cone shape but bulge a tiny bit out at 
>> the middle. I acchieved this by using a vertically very elongated sphere, 
>> cut at the middle (i.e. the base of the column) and at the place where 
>> the top should be. You have to experiment with the vertical elongation 
>> until you have both bottom and top diameters correctly. An easy way to do 
>> this is to first make a proxy model in Moray to get the measurements 
>> needed.
>
> Yes, my approach too.  I saw somewhere on the web that Roman columns have 
> more of a middle bulge but Greek have a curved taper but the base is the 
> thickest.  No idea if they knew what they were talking about.
> http://www.uen.org/Centennial/08BuildingsA.html
Yes, the entasis (I forgot the name). I followed the Greek method. 
Interestingly, I have a paper describing the 'blueprints' used by the Greek 
in constructing the Apollo temple at Didyma in Turkey. They scratched the 
plans on the walls or the floor under construction and took their 
measurements from there. After completion, walls and floors were polished 
and the scratchings removed. Thanks to the fact that the Apollo temple was 
never finished, the blueprints survived.
In the same temple can be seen that they first built the columns and only 
afterwards carved the flutes. The following French site gives some fair 
examples of the ruins.
http://jfbradu.free.fr/GRECEANTIQUE/turquie/didymes/didymes-bas.htm

Thomas

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Jim Charter wrote:

> ... you used boolean subtraction of torii?  Again I have been
> trying exactly the same approach but with POV CSG.  The problem
> I had was getting the circumference of the torus to decrease at
> an rate appropriate to the diminishing circumference of the tapering
> shaft.

How about sphere_sweeps for column and flutes? Evaluating the spline
functions would give any circumference you need.

 -Shay

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