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"Kenneth" <kdw### [at] gmail com> wrote:
> 2) Try applying a JPEG image instead of a PNG (made in a graphics program with a
> transparent mask in the outer area)...
Sorry, ignore that; I wasn't thinking. (A jpeg image can't have an alpha-channel
mask, AFAIK.) Duh.
INSTEAD...
Try applying a jpeg image to the glass with the 'once' keyword (instead of your
png image), to see if there is any visual change in the transparent areas. I'm
still thinking that the 'darkness' problem might be PNG/gamma related.
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> I thought that I would try this with a transparent texture.
> Unfortunately this is the best I could get. Your method is better.
> I used a png with a RGB=0 set to transparent. You can see the darkened
> area of the transparent part of the image map. Also the copy of the
> image at the back is a question mark. It is not a reflection.
Looks like a reflection to me.
As for the alpha thing, it might be worth trying `use_alpha on` in the
finish block. That'll turn off that texture layer's highlights and
specular reflections wherever the image is transparent.
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On 25/10/2018 23:23, Kenneth wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>
>> 2) Try applying a JPEG image instead of a PNG (made in a graphics program with a
>> transparent mask in the outer area)...
>
> Sorry, ignore that; I wasn't thinking. (A jpeg image can't have an alpha-channel
> mask, AFAIK.) Duh.
>
> INSTEAD...
> Try applying a jpeg image to the glass with the 'once' keyword (instead of your
> png image), to see if there is any visual change in the transparent areas. I'm
> still thinking that the 'darkness' problem might be PNG/gamma related.
>
>
How right you were. I use Paint Shop Pro for image editing. Hidden away
in File Format Preferences, is the setting: Load and save transparency
to / from layer transparency OR Load and save transparency to / from
alpha channel. It was set to layer transparency. Changing it to alpha
solved the problem. I had to reinstall PSP a year or so ago and had
forgotten those settings. So does that mean there is a problem when
using the colour pallet for transparency?
Clipka was right about the reflection. My brain must have been addled
forgotten setting.
--
Regards
Stephen
Post a reply to this message
Attachments:
Download 'label_c_b3_c0000.png' (235 KB)
Preview of image 'label_c_b3_c0000.png'
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On 25/10/2018 23:08, StephenS wrote:
> On 2018-10-25 1:58 p.m., Stephen wrote:
> ....
>> I thought that I would try this with a transparent texture.
>> Unfortunately this is the best I could get. Your method is better.
>> I used a png with a RGB=0 set to transparent. You can see the darkened
>> area of the transparent part of the image map. Also the copy of the
>> image at the back is a question mark. It is not a reflection.
>>
> My texture is:
>
> #declare Nova_Scotia_Crest_ =
> texture {
> pigment {
> image_map{
> png
> "E:/Documents/Bishop3d/Objects/Glass_containers/Nova_Scotia_image.png"
> map_type 0
> once
> }
> scale <1.000,1.250,1.000>
> translate <-0.500,0.750,0.000>
> }
>
> }
>
I'll show you mine.
#declare Glass_Image =
material{
texture {
#declare BISHOP3D_TEMPORARY_IDENTIFIER =
texture {
pigment {
colour rgbft <0.259,0.384,0.200,0.000,0.950>
}
finish {
ambient rgb <0.000,0.000,0.000>
brilliance 1.000
crand 0.000
diffuse 0.190
metallic 0.000
phong 0.000
phong_size 40.000
specular 1.000
roughness 0.001
conserve_energy
reflection {
rgb <0.040,0.040,0.040>, rgb <0.500,0.500,0.500>
fresnel 0
falloff 1.500
exponent 2.000
metallic 0.000
}
irid {
0.275
thickness 0.100
turbulence 0.000
}
}
}
texture {
pigment {
image_map{
png "F:\Graphics\B3D Data\Maps\Odds\Mask_1a.png"
map_type 2
once
}
scale <2.000,2.000,2.000>
translate <-0.500,-0.500,-0.500>
}
finish {
ambient rgb <0.000,0.000,0.000>
brilliance 1.000
crand 0.000
diffuse 0.850
metallic 0.000
phong 0.000
phong_size 40.000
specular 1.000
roughness 0.001
conserve_energy
reflection {
rgb <0.040,0.040,0.040>, rgb <0.040,0.040,0.040>
fresnel 0
falloff 1.500
exponent 2.000
metallic 0.000
}
}
}
;/* the semicolon is necessary or POV-Ray will not figure out that
the declarations has ended /*
BISHOP3D_TEMPORARY_IDENTIFIER
}
interior{
ior 2.010
caustics 0.000
dispersion 1.030
dispersion_samples 7.000
fade_power 0.000
fade_distance 0.000
fade_color rgb <0.000,0.000,0.000>
}
}
> I think all of the magic is in the alpha channel, in a graphics program
> (Gimp) it looks like a black/white mask.
>
I need to do some reading on the png file format, transparency and alpha.
--
Regards
Stephen
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On 26/10/2018 10:06, Stephen wrote:
>
> How right you were. I use Paint Shop Pro for image editing. Hidden away
> in File Format Preferences, is the setting: Load and save transparency
> to / from layer transparency OR Load and save transparency to / from
> alpha channel. It was set to layer transparency. Changing it to alpha
> solved the problem.
Wrong. :(
I'll start a new thread if I find a solution or need help.
--
Regards
Stephen
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clipka <ano### [at] anonymousorg> wrote:
>
> As for the alpha thing, it might be worth trying `use_alpha on` in the
> finish block. That'll turn off that texture layer's highlights and
> specular reflections wherever the image is transparent.
Is that an undocumented feature of use_alpha? (Or perhaps I'm not reading the
docs correctly?) In '3.6.2.6.4 Using the Alpha Channel', the only thing I see
there that might give a clue is this:
"Note: The following mechanism has some limitations with colored highlights:
When generating non-premultiplied alpha output to a classic low-dynamic-range
file format (e.g. PNG), transparency of particularly bright areas will now be
reduced, in order to better preserve highlights on transparent objects."
But that description seems to imply the opposite of 'turning off' the
highlights.
Mea culpa: I've never used the 'use_alpha' keyword, so I don't really know what
visual effect it produces.
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"Kenneth" <kdw### [at] gmailcom> wrote:
> clipka <ano### [at] anonymousorg> wrote:
>
> >
> > As for the alpha thing, it might be worth trying `use_alpha on` in the
> > finish block. That'll turn off that texture layer's highlights and
> > specular reflections wherever the image is transparent.
>
> Is that an undocumented feature of use_alpha?
No...
Imagine use_alpha as being sort of a texture map.
In the areas of the image map that have an alpha-channel "flag" for those
pixels, POV-Ray turns it on, which negates the texture - including the
highlights and specular reflections of the finish so that it's truly invisible -
NOT just clear yet still reflective like glass.
http://wiki.povray.org/content/Reference:Finish
New in version 3.8 you can now specify use_alpha in the finish block. If set to
off, the default and also the old behavior, then pigment filter and transmit
only hide the surface's diffuse, ambient and emission components. If set to on
then pigment filter and transmit also hide the surface's highlights and specular
reflection.
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Am 26.10.2018 um 19:28 schrieb Kenneth:
>> As for the alpha thing, it might be worth trying `use_alpha on` in the
>> finish block. That'll turn off that texture layer's highlights and
>> specular reflections wherever the image is transparent.
>
> Is that an undocumented feature of use_alpha? (Or perhaps I'm not reading the
> docs correctly?) In '3.6.2.6.4 Using the Alpha Channel', the only thing I see
> there that might give a clue is this:
>
> "Note: The following mechanism has some limitations with colored highlights:
That's the documentation on alpha channel /output/. What we're looking
at here is alpha channel /input/, which for the most part is documented
in the section on image_map, including the old `use_alpha` mechanism.
But the additional new use of `use_alpha` keyword in the finish block is
documented in the section on finish (pretty much as a side note). As a
matter of fact it not only applies to image_map, but any pigment that
features transparency.
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[Bald Eagle wrote:]
> > http://wiki.povray.org/content/Reference:Finish
[Clipka wrote:]
>
> That's the documentation on alpha channel /output/. What we're looking
> at here is alpha channel /input/, which for the most part is documented
> in the section on image_map, including the old `use_alpha` mechanism.
>
> But the additional new use of `use_alpha` keyword in the finish block is
> documented in the section on finish (pretty much as a side note)...
Thanks. All clear now.
I see now that my confusion is just documentation-related. The keyword index for
'use_alpha' (in the 'newer' documentation that can be downloaded for v3.7.1 etc)
takes the user to only one docs section, 3.6.2.4.2 Image Pattern --with only a
single link there to "Using the Alpha Channel". Seems that the keyword should
instead have two (or three?) entries in the index, additionally for 'Finish' and
'image_map'.
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On 25/10/2018 23:08, StephenS wrote:
> I think all of the magic is in the alpha channel,
Yes, the alpha channel of the image map is the key. I think that I have
worked out how to make one in the right proportions.
I prefer my medicine in a taller glass.
--
Regards
Stephen
Post a reply to this message
Attachments:
Download 'test_k4b_0000.png' (405 KB)
Preview of image 'test_k4b_0000.png'
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