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Nested, mostly transparent spheres - cylindrical pattern oriented toward camera
- where reflection is coloured and conserve energy is off. Reflection is of a
gray bozo pattern, here via no-image spheres just around the visible spheres.
The look of these I like, but I have found it impossible, so far, to use this
technique as part of a larger scene without artefacts. I am after antique,
frosted Christmas lights like I remember my grandmother having a few of on her
tree when I was a kid.
Post a reply to this message
Attachments:
Download 'bulbtest.jpg' (112 KB)
Preview of image 'bulbtest.jpg'
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"William Pokorny" <pokorny_epix_net> wrote:
> Nested, mostly transparent spheres - cylindrical pattern oriented toward camera
> - where reflection is coloured and conserve energy is off. Reflection is of a
> gray bozo pattern, here via no-image spheres just around the visible spheres.
>
> The look of these I like, but I have found it impossible, so far, to use this
> technique as part of a larger scene without artefacts. I am after antique,
> frosted Christmas lights like I remember my grandmother having a few of on her
> tree when I was a kid.
However they are nice.
And with a bit of turbulence can become nebulae...
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> The look of these I like, but I have found it impossible, so far, to use this
> technique as part of a larger scene without artefacts.
What kind of artefacts?
Often artefacts appear with transparent objects when max_trace_level is too low.
Regards,
Simone
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Hi Simone,
Thank you for the suggestion and in one instance I did try and increase that
setting.
Artefacts is probably not the best term - limitations might be better. For
example, in the coloured bulbs image I put an individual, randomised, bozo
sphere around each so the colour pattern reflected would be different. I started
with the idea of putting the texture on the inside of a hollow sphere, but could
not get the reflection-amplification effect to work at all that way. Eventually
I got there with a transmit filter on the outside of the sphere using
no_reflection, no_shadow for those spheres - but I could not use no_image
because then I lost the transmit filter. Long winded way to say that when I try
to build a scene around these type of "bulbs," the edges of this outer sphere
show up and the illusion is broken.
The attached image instead reflects a bozo pattern from a sky sphere (why this
works and inside texture did not, I do not know). I put a bit of a cage around
this one, but all the shapes in the cage cannot cast shadows or again the
illusion breaks down. The lack of shadows itself causes the illusion to break
down.
Aside: The X-ray effect you are after is by the way similar to the way the
texture needs to be patterned on each sphere. An AOI pattern would make this
trick easier in that I would not have to reorient the spheres individually to
the camera position, but it wouldn't remove the limitations I am hitting. It
would, I think, make the effect complete for rays not coming directly from the
camera position if the AOI pattern would be in effect for all rays.
I am thinking now that I might have to create the texture I want and stick it on
the bulbs with ambient 1, but I have yet to try it. There is also media, but I
have struggled in the past to get the look I want with media for these kinds of
effects. And there is Mr Lipka's new "diffuse-backside illumination" feature in
beta 34 that might be useful here, but I am still on 33 with my linux compile.
Anyway, sorry for thinking aloud. Thanks again for the suggestion.
Regards, Bill
"mone" <mon### [at] alienenterprises de> wrote:
> What kind of artefacts?
> Often artefacts appear with transparent objects when max_trace_level is too low.
>
> Regards,
> Simone
Post a reply to this message
Attachments:
Download 'fireincage.jpg' (207 KB)
Preview of image 'fireincage.jpg'
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William Pokorny schrieb:
> And there is Mr Lipka's new "diffuse-backside illumination" feature in
> beta 34 that might be useful here, but I am still on 33 with my linux compile.
Don't put too high hopes into it. I guess it would work great and easy
if backside illumination also included specular highlights, but it
deliberately doesn't.
You might get acceptable results with this approach though by moving the
interior light source a deal towards the camera.
As for beta.33, double_illuminate will likely do the same trick; the
major difference is that it ignores radiosity and photons (which may
actually be of benefit in this case), and that you cannot control the
intensity of front- vs. backside-illumination, but in this case you can
achieve the same by tweaking the light source intensity.
To control the falloff of the light spot, you can tweak various parameters:
- The light source's offset from the center (zero offset won't do)
- The light source's distance-based falloff
- The brilliance parameter
Yet another, completely different approach would be to use light groups,
placing each bulb in its own light group together with a light source
straight in front of it, to generate a classic highlight.
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"William Pokorny" <pokorny_epix_net> wrote:
> Artefacts is probably not the best term - limitations might be better. For
> example, in the coloured bulbs image I put an individual, randomised, bozo
> sphere around each so the colour pattern reflected would be different. I started
> with the idea of putting the texture on the inside of a hollow sphere, but could
> not get the reflection-amplification effect to work at all that way. Eventually
> I got there with a transmit filter on the outside of the sphere using
> no_reflection, no_shadow for those spheres - but I could not use no_image
> because then I lost the transmit filter. Long winded way to say that when I try
> to build a scene around these type of "bulbs," the edges of this outer sphere
> show up and the illusion is broken.
Oh, that sounds very complicated. I'm not sure whether I've understood it
completely. I once had made an earth globe with a frosted rim like appearance. I
have adapted the code a bit, so that it might look a little like the frosted
bauble you are looking for. But maybe the bozo texture thing is not quite what
you were looking for? Because there's not much bozo in the middle of the sphere.
However, you only need one sphere, at least and not an additional outer one in
this case.
Regards,
Simone
/////////////////////////////////////////
camera {
location <0.0, -1, -23.5>
look_at <0.0, 0.0, 0.0>
right x*image_width/image_height
angle 30
}
light_source { <0, 0, 3.5> color rgb <-.15 ,1, 1>*55 shadowless } //
light behind sphere for frosted rim
light_source { /// light inside sphere
0*x
color rgb <4,1,1>*2
translate <0, 0, 0>
}
light_source { /// normal light (works without too)
0*x
color rgb <1,1,1>*.5
translate <0, 0, -20>
}
sphere
{
<0, 0, 0>
3.0
texture { pigment { color rgbt <.25,.01,0.01,.3> } }
texture {
pigment {
bozo
color_map {
[0.0 color rgbt <.0, .0, .0, .67> ]
[1 color rgbt <.2, .2, .2, 1> ]
}
scale .6
}
}
finish { phong .3 phong_size 5 ambient .4}
hollow on
}
/////////////////////////
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Attachments:
Download 'bauble_test.jpg' (23 KB)
Preview of image 'bauble_test.jpg'
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I have been known to make things more complicated than they need to be... :-)
The look of your light bulb would be fine for the Holiday image I have in mind.
I'll give the technique a go in addition to trying some of the ideas suggested
by Mr Lipka. Hopefully something works out in the larger image. Thanks to both
of you!
Best regards, Bill
"mone" <mon### [at] alienenterprisesde> wrote:
>
> Oh, that sounds very complicated. I'm not sure whether I've understood it
> completely. I once had made an earth globe with a frosted rim like appearance. I
> have adapted the code a bit, so that it might look a little like the frosted
> bauble you are looking for. But maybe the bozo texture thing is not quite what
> you were looking for? Because there's not much bozo in the middle of the sphere.
> However, you only need one sphere, at least and not an additional outer one in
> this case.
>
> Regards,
>
> Simone
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> "William Pokorny" <pokorny_epix_net> wrote:
>
>> Artefacts is probably not the best term - limitations might be better. For
>> example, in the coloured bulbs image I put an individual, randomised, bozo
>> sphere around each so the colour pattern reflected would be different. I started
>> with the idea of putting the texture on the inside of a hollow sphere, but could
>> not get the reflection-amplification effect to work at all that way. Eventually
>> I got there with a transmit filter on the outside of the sphere using
>> no_reflection, no_shadow for those spheres - but I could not use no_image
>> because then I lost the transmit filter. Long winded way to say that when I try
>> to build a scene around these type of "bulbs," the edges of this outer sphere
>> show up and the illusion is broken.
>
> Oh, that sounds very complicated. I'm not sure whether I've understood it
> completely. I once had made an earth globe with a frosted rim like appearance. I
> have adapted the code a bit, so that it might look a little like the frosted
> bauble you are looking for. But maybe the bozo texture thing is not quite what
> you were looking for? Because there's not much bozo in the middle of the sphere.
> However, you only need one sphere, at least and not an additional outer one in
> this case.
>
> Regards,
>
> Simone
>
> /////////////////////////////////////////
> camera {
> location <0.0, -1, -23.5>
> look_at <0.0, 0.0, 0.0>
>
> right x*image_width/image_height
>
> angle 30
>
> }
>
> light_source { <0, 0, 3.5> color rgb <-.15 ,1, 1>*55 shadowless } //
> light behind sphere for frosted rim
>
> light_source { /// light inside sphere
> 0*x
> color rgb <4,1,1>*2
> translate <0, 0, 0>
> }
>
> light_source { /// normal light (works without too)
> 0*x
> color rgb <1,1,1>*.5
> translate <0, 0, -20>
> }
>
> sphere
> {
> <0, 0, 0>
> 3.0
> texture { pigment { color rgbt <.25,.01,0.01,.3> } }
>
> texture {
> pigment {
> bozo
> color_map {
>
> [0.0 color rgbt <.0, .0, .0, .67> ]
> [1 color rgbt <.2, .2, .2, 1> ]
> }
> scale .6
> }
> }
>
> finish { phong .3 phong_size 5 ambient .4}
> hollow on
>
> }
> /////////////////////////
>
>
> ------------------------------------------------------------------------
>
Why the hollow on?
You don't use any media. hollow's one and only use/purpose is to enable
an object to contain a media or be filled with fog. Nothing else!
Alain
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