Hi, I've been playing around with POVRAY tutorials the past day and a half and
really enjoying the program. Today I decided I would try to make a "disco ball"
formed by a spherical shell with holes in it, each hole being filled with a
transparent material of varying color.  However, I'm having trouble getting it
to work with the variable color. Let me show you my code to show you what I
mean:

global_settings {max_trace_level 60}

#declare shell = difference{
sphere{<0,0,0> 6}
sphere{<0,0,0> 5}}

light_source{<100,0,0> color rgb <1,1,1>}

light_source{<0,0,0> color rgb <1,1,1>}

camera{location <10,1,1> look_at<0,0,0>}



// just a bunch of cylinders uniformly distributed on a sphere with 30 degrees
// separation in the theta/phi angular coordinates

#declare bunch_of_cylinders= union{cylinder {<0,0,0>,< 0.0 , 0.0 , 10.0 >0.5 tex
ture { pigment { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 5.0 , 0.0 , 8.66025403784 >0.5 texture { pigment { color rgb
 < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 8.66025403784 , 0.0 , 5.0 >0.5 texture { pigment { color rgb
 < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 10.0 , 0.0 , 6.12303176911e-16 >0.5 texture { pigment { colo
r rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 8.66025403784 , 0.0 , -5.0 >0.5 texture { pigment { color rg
b < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 5.0 , 0.0 , -8.66025403784 >0.5 texture { pigment { color rg
b < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 5.66549845232e-15 , 0.0 , -10.0 >0.5 texture { pigment { col
or rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 0.0 , 0.0 , 10.0 >0.5 texture { pigment { color rgb < 0 , 1
, 0 >}}}
cylinder {<0,0,0>,< 4.33012701892 , 2.5 , 8.66025403784 >0.5 texture { pigment {
 color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 7.5 , 4.33012701892 , 5.0 >0.5 texture { pigment { color rgb
 < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 8.66025403784 , 5.0 , 6.12303176911e-16 >0.5 texture { pigme
nt { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 7.5 , 4.33012701892 , -5.0 >0.5 texture { pigment { color rg
b < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 4.33012701892 , 2.5 , -8.66025403784 >0.5 texture { pigment
{ color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 4.90646558481e-15 , 2.83274922616e-15 , -10.0 >0.5 texture {
 pigment { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 0.0 , 0.0 , 10.0 >0.5 texture { pigment { color rgb < 0 , 0
, 1 >}}}
cylinder {<0,0,0>,< 2.5 , 4.33012701892 , 8.66025403784 >0.5 texture { pigment {
 color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 4.33012701892 , 7.5 , 5.0 >0.5 texture { pigment { color rgb
 < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 5.0 , 8.66025403784 , 6.12303176911e-16 >0.5 texture { pigme
nt { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 4.33012701892 , 7.5 , -5.0 >0.5 texture { pigment { color rg
b < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 2.5 , 4.33012701892 , -8.66025403784 >0.5 texture { pigment
{ color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 2.83274922616e-15 , 4.90646558481e-15 , -10.0 >0.5 texture {
 pigment { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 0.0 , 0.0 , 10.0 >0.5 texture { pigment { color rgb < 1 , 0
, 0 >}}}
cylinder {<0,0,0>,< 3.06151588456e-16 , 5.0 , 8.66025403784 >0.5 texture { pigme
nt { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 5.30270106023e-16 , 8.66025403784 , 5.0 >0.5 texture { pigme
nt { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 6.12303176911e-16 , 10.0 , 6.12303176911e-16 >0.5 texture {
pigment { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 5.30270106023e-16 , 8.66025403784 , -5.0 >0.5 texture { pigm
ent { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 3.06151588456e-16 , 5.0 , -8.66025403784 >0.5 texture { pigm
ent { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 3.46900270114e-31 , 5.66549845232e-15 , -10.0 >0.5 texture {
 pigment { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -0 , 0.0 , 10.0 >0.5 texture { pigment { color rgb < 0 , 1 ,
 0 >}}}
cylinder {<0,0,0>,< -2.5 , 4.33012701892 , 8.66025403784 >0.5 texture { pigment
{ color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -4.33012701892 , 7.5 , 5.0 >0.5 texture { pigment { color rg
b < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -5.0 , 8.66025403784 , 6.12303176911e-16 >0.5 texture { pigm
ent { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -4.33012701892 , 7.5 , -5.0 >0.5 texture { pigment { color r
gb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -2.5 , 4.33012701892 , -8.66025403784 >0.5 texture { pigment
 { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -2.83274922616e-15 , 4.90646558481e-15 , -10.0 >0.5 texture
{ pigment { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -0 , 0.0 , 10.0 >0.5 texture { pigment { color rgb < 0 , 0 ,
 1 >}}}
cylinder {<0,0,0>,< -4.33012701892 , 2.5 , 8.66025403784 >0.5 texture { pigment
{ color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -7.5 , 4.33012701892 , 5.0 >0.5 texture { pigment { color rg
b < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -8.66025403784 , 5.0 , 6.12303176911e-16 >0.5 texture { pigm
ent { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -7.5 , 4.33012701892 , -5.0 >0.5 texture { pigment { color r
gb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -4.33012701892 , 2.5 , -8.66025403784 >0.5 texture { pigment
 { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -4.90646558481e-15 , 2.83274922616e-15 , -10.0 >0.5 texture
{ pigment { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -0 , 0.0 , 10.0 >0.5 texture { pigment { color rgb < 1 , 0 ,
 0 >}}}
cylinder {<0,0,0>,< -5.0 , 2.83274922616e-15 , 8.66025403784 >0.5 texture { pigm
ent { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -8.66025403784 , 4.90646558481e-15 , 5.0 >0.5 texture { pigm
ent { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -10.0 , 5.66549845232e-15 , 6.12303176911e-16 >0.5 texture {
 pigment { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -8.66025403784 , 4.90646558481e-15 , -5.0 >0.5 texture { pig
ment { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -5.0 , 2.83274922616e-15 , -8.66025403784 >0.5 texture { pig
ment { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -5.66549845232e-15 , 3.20978727133e-30 , -10.0 >0.5 texture
{ pigment { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -0 , -0 , 10.0 >0.5 texture { pigment { color rgb < 0 , 1 ,
0 >}}}
cylinder {<0,0,0>,< -4.33012701892 , -2.5 , 8.66025403784 >0.5 texture { pigment
 { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -7.5 , -4.33012701892 , 5.0 >0.5 texture { pigment { color r
gb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -8.66025403784 , -5.0 , 6.12303176911e-16 >0.5 texture { pig
ment { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -7.5 , -4.33012701892 , -5.0 >0.5 texture { pigment { color
rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -4.33012701892 , -2.5 , -8.66025403784 >0.5 texture { pigmen
t { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -4.90646558481e-15 , -2.83274922616e-15 , -10.0 >0.5 texture
 { pigment { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -0 , -0 , 10.0 >0.5 texture { pigment { color rgb < 0 , 0 ,
1 >}}}
cylinder {<0,0,0>,< -2.5 , -4.33012701892 , 8.66025403784 >0.5 texture { pigment
 { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -4.33012701892 , -7.5 , 5.0 >0.5 texture { pigment { color r
gb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -5.0 , -8.66025403784 , 6.12303176911e-16 >0.5 texture { pig
ment { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -4.33012701892 , -7.5 , -5.0 >0.5 texture { pigment { color
rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -2.5 , -4.33012701892 , -8.66025403784 >0.5 texture { pigmen
t { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -2.83274922616e-15 , -4.90646558481e-15 , -10.0 >0.5 texture
 { pigment { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -0 , -0 , 10.0 >0.5 texture { pigment { color rgb < 1 , 0 ,
0 >}}}
cylinder {<0,0,0>,< -9.18454765367e-16 , -5.0 , 8.66025403784 >0.5 texture { pig
ment { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -1.59081031807e-15 , -8.66025403784 , 5.0 >0.5 texture { pig
ment { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -1.83690953073e-15 , -10.0 , 6.12303176911e-16 >0.5 texture
{ pigment { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< -1.59081031807e-15 , -8.66025403784 , -5.0 >0.5 texture { pi
gment { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< -9.18454765367e-16 , -5.0 , -8.66025403784 >0.5 texture { pi
gment { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< -1.04070081034e-30 , -5.66549845232e-15 , -10.0 >0.5 texture
 { pigment { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 0.0 , -0 , 10.0 >0.5 texture { pigment { color rgb < 0 , 1 ,
 0 >}}}
cylinder {<0,0,0>,< 2.5 , -4.33012701892 , 8.66025403784 >0.5 texture { pigment
{ color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 4.33012701892 , -7.5 , 5.0 >0.5 texture { pigment { color rg
b < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 5.0 , -8.66025403784 , 6.12303176911e-16 >0.5 texture { pigm
ent { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 4.33012701892 , -7.5 , -5.0 >0.5 texture { pigment { color r
gb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 2.5 , -4.33012701892 , -8.66025403784 >0.5 texture { pigment
 { color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 2.83274922616e-15 , -4.90646558481e-15 , -10.0 >0.5 texture
{ pigment { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 0.0 , -0 , 10.0 >0.5 texture { pigment { color rgb < 0 , 0 ,
 1 >}}}
cylinder {<0,0,0>,< 4.33012701892 , -2.5 , 8.66025403784 >0.5 texture { pigment
{ color rgb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 7.5 , -4.33012701892 , 5.0 >0.5 texture { pigment { color rg
b < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 8.66025403784 , -5.0 , 6.12303176911e-16 >0.5 texture { pigm
ent { color rgb < 0 , 0 , 1 >}}}
cylinder {<0,0,0>,< 7.5 , -4.33012701892 , -5.0 >0.5 texture { pigment { color r
gb < 1 , 0 , 0 >}}}
cylinder {<0,0,0>,< 4.33012701892 , -2.5 , -8.66025403784 >0.5 texture { pigment
 { color rgb < 0 , 1 , 0 >}}}
cylinder {<0,0,0>,< 4.90646558481e-15 , -2.83274922616e-15 , -10.0 >0.5 texture
{ pigment { color rgb < 0 , 0 , 1 >}}}
}


//object{bunch_of_cylinders}


// this is how I generate the shape of the material that will fill the holes

#declare cutouts =
intersection{
object{shell}
object{bunch_of_cylinders}
}

// this is how i generate a spherical shell with holes in it

#declare shell_with_cylindercutouts = difference{
object{shell}
object{bunch_of_cylinders}
}

// and this is putting the spherical shell with holes in it with the filled
//holes

union{
object{shell_with_cylindercutouts texture {pigment{color rgb<0,0,0>}}}
object{cutouts}}


The problem with the above code is the last line. POVRAY doesn't like that
"cutouts" doesn't have a color. But of course I want cutouts to have the color
of "bunch_of_cylinders" from which it was built. From my definition of cutouts I
don't specify any color, but I imagine there's a way for me to choose which
color from the intersection gets picked up by the defined object?

I hope that I'm making sense. I appreciate any help I can get!

Thanks.
Brad

Post a reply to this message

On 10/03/2010 04:42 AM, Brad wrote:
> #declare shell = difference{
> sphere{<0,0,0> 6}
> sphere{<0,0,0> 5}}

try assigning a pigment to the above and that might better visualize
whats going on here ...

> // and this is putting the spherical shell with holes in it with the filled
> //holes
> 
> union{
> object{shell_with_cylindercutouts texture {pigment{color rgb<0,0,0>}}}
> object{cutouts}}

then comment out the union stuff and look at the "cutouts" only ... I
didn't try it but I think having the "bunch_of_cyclinders" extend beyond
the outer skin of the "shell" is the problem.

Post a reply to this message

Jim Holsenback <jho### [at] povrayorg> wrote:
> On 10/03/2010 04:42 AM, Brad wrote:
> > #declare shell = difference{
> > sphere{<0,0,0> 6}
> > sphere{<0,0,0> 5}}
>
> try assigning a pigment to the above and that might better visualize
> whats going on here ...
>
> > // and this is putting the spherical shell with holes in it with the filled
> > //holes
> >
> > union{
> > object{shell_with_cylindercutouts texture {pigment{color rgb<0,0,0>}}}
> > object{cutouts}}
>
> then comment out the union stuff and look at the "cutouts" only ... I
> didn't try it but I think having the "bunch_of_cyclinders" extend beyond
> the outer skin of the "shell" is the problem.

I don't think there is a problem with this. If I add color to the
bunch_of_cylinders as a whole the image looks correct ( see
http://yfrog.com/nccodelp ).

I mean, I do know a way of fixing the problem, (by defining an intersection with
the shell and each individual cylinder, giving each a color attribute) but I
have to modify the code quite a bit and was hoping to that there was something
else I could do to preserve the color of the cylinders.

I don't think the cylinders extending outside the shell is a problem. I think
that's the way it should be done when taking a "difference". The tutorial that I
read said that if the two objects overlap perfectly on the boundary, then POVRAY
sometimes gets confused and I might not actually get a hole in the cylinder. So
I "difference" the entire cylinder to make sure that I get a hole in the shell.
Then I fill that hole with the correct size "cutout" which is generated via a
'intersection'.


NOTE: In my first code submitted it wouldn't have worked the way I wanted anyway
because I didn't give each color a transparency to it. But POVRAY does
explicitly say

"  0:00:00 Parsing
File: code.pov  Line: 142
Parse Warning: No pigment type given."

so that isn't the issue to my problem. Making each color transparent still gives
this error and doesn't give me what I expect.

Post a reply to this message

> On 10/03/2010 04:42 AM, Brad wrote:
>> #declare shell = difference{
>> sphere{<0,0,0>  6}
>> sphere{<0,0,0>  5}}
>
> try assigning a pigment to the above and that might better visualize
> whats going on here ...
>
>> // and this is putting the spherical shell with holes in it with the filled
>> //holes
>>
>> union{
>> object{shell_with_cylindercutouts texture {pigment{color rgb<0,0,0>}}}
>> object{cutouts}}
>
> then comment out the union stuff and look at the "cutouts" only ... I
> didn't try it but I think having the "bunch_of_cyclinders" extend beyond
> the outer skin of the "shell" is the problem.

There is nothing wrong with the warning, and it don't point to the real 
problem.

The extent of an object relative to another don't have any effect exept 
preventing coincident surfaces artefacts.

Whenever you use a difference or intersections, the various surfaces 
take the texture of the object that define THAT surface. The end of the 
cutouts thake their colouration from the sphere and their sides from the 
cylinders.

Here's the real problem:
You have the shell with the holes. The sides of the holes ARE coloured.
You have the cutouts. The sides of those are also coloured.
Then, you union both, reconstructing the original sphere.
The coloured parts are there but hiden inside the thickhess of the shell.

You need to make your pierced shell, then place coloured and transparent 
pieces into the holes.
You can make some sets of cutouts and give each the desided colouration. 
One red set, one green set and one blue set in your case.

A side note: Why not let POV-Ray compute the end points of your 
cylinders? Just use a cylinder like this one:
cylinder{0, 10*x, 0.5}
Then, you rotate it to where you want it. This gives you a cleaner code.
Also, when you have very small values like 5.66549845232e-15, you can 
replace them with 0 (zero), the difference is absolutely negligeable. In 
fact, usualy, any value smaller than 1e-6 can be changed to zero.



Alain

Post a reply to this message

Hi Alain,


> Whenever you use a difference or intersections, the various surfaces
> take the texture of the object that define THAT surface. The end of the
> cutouts thake their colouration from the sphere and their sides from the
> cylinders.


Ahh, I did not realize this. That fact helps a lot.



> You need to make your pierced shell, then place coloured and transparent
> pieces into the holes.
> You can make some sets of cutouts and give each the desided colouration.
> One red set, one green set and one blue set in your case.

I see that I must go this route now. Thanks.

>
> A side note: Why not let POV-Ray compute the end points of your
> cylinders? Just use a cylinder like this one:
> cylinder{0, 10*x, 0.5}

Does "10*x" simply mean <10,0,0>? I'm guessing so. I don't see how that would
make it all that much cleaner though because then I would have to determine the
rotation to place it where I wanted for each one and each cylinder would then
have more data specifying it than in my original case. Unless I misunderstand...


> Then, you rotate it to where you want it. This gives you a cleaner code.
> Also, when you have very small values like 5.66549845232e-15, you can
> replace them with 0 (zero), the difference is absolutely negligeable. In
> fact, usualy, any value smaller than 1e-6 can be changed to zero.

Yes, that's definitely true. But I generate the cylindrical syntax from a python
script that I wrote, and that is how it's outputted with no formatting. I could
make it cleaner and have it report 0 instead of these really small numbers, but
I wasn't intending to use the bunch_of_cylinders block as something that I
planned to read and change by hand anyway.

Thanks for your help! I'll make the changes after lunch and see how it looks!

Post a reply to this message

On 10/03/2010 03:20 PM, Alain wrote:
> You need to make your pierced shell, then place coloured and transparent
> pieces into the holes.

ha-ha ... I thought making the shell yellow instead of black (without
any sky_sphere) would have led to that discovery ;-)

Post a reply to this message

Jim Holsenback <jho### [at] povrayorg> wrote:
> On 10/03/2010 03:20 PM, Alain wrote:
> > You need to make your pierced shell, then place coloured and transparent
> > pieces into the holes.
>
> ha-ha ... I thought making the shell yellow instead of black (without
> any sky_sphere) would have led to that discovery ;-)

Hmm, good point. Here's what I think you are suggesting:

http://yfrog.com/epcodebp

And you can see the problem from this image. A somewhat unrelated question: I
have a light source in the center of the sphere. Is there a way to make that
light source brighter?

Thanks,
Brad

Post a reply to this message

On 03/10/2010 8:46 PM, Brad wrote:
> And you can see the problem from this image. A somewhat unrelated question: I
> have a light source in the center of the sphere. Is there a way to make that
> light source brighter?

A quick answer is yes. Just multiply the colour like:

colour rgb <1,1,1> * 10

Or

colour rgb <10,10,10>



-- 

Best Regards,
	Stephen

Post a reply to this message

On 10/03/2010 04:46 PM, Brad wrote:
> A somewhat unrelated question: I
> have a light source in the center of the sphere. Is there a way to make that
> light source brighter?

nothing wrong with rgb <2,2,0> for a light color ... fade_distance, and
fade_power are options. Be sure you check out:

http://aries/wiki/index.php/Documentation:Reference_Section_4.3#Light_Sources

depending on the "look" you're going for there might be ways to do this
other than using a light source ... there's more than one way to trace a
ray! ;-)

Post a reply to this message

On 10/03/2010 05:19 PM, Jim Holsenback wrote:
> On 10/03/2010 04:46 PM, Brad wrote:
>> A somewhat unrelated question: I
>> have a light source in the center of the sphere. Is there a way to make that
>> light source brighter?
> 
> nothing wrong with rgb <2,2,0> for a light color ... fade_distance, and
> fade_power are options. Be sure you check out:
> 
> http://aries/wiki/index.php/Documentation:Reference_Section_4.3#Light_Sources

sheesh ... long day ... this addy would probably do better!

http://wiki.povray.org/content/Documentation:Reference_Section_4.3#Light_Sources

Post a reply to this message