I have been thinking about a new way of specifying transparence, rgbft
seems too limiting.
The new way would look like this:

New pattern: solid OFFSET//where OFFSET is the point on the color map(or
whatever map)

transparence {//this would either go under texture or pigment, probably
the latter
    multiplicative PATTERN
    additive PATTERN
    subractive PATTERN
    filter PATTERN
    transmit PATTERN

    pigment {}//an optional pigment, if present, this is used for
transparence calculations
}

It would allow a separate pigment for the transparence calculations, and
would allow one to have an object of one color filter light like an
object of another color(I believe there are some real-world substances
which actually do this).
It would be very useful in layered textures, and would make some very
interesting surrealistic scenes possible. Also, it might make good
clouds when used with the layered objects approach.

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Chris Huff wrote in message <378### [at] compuservecom>...
>I have been thinking about a new way of specifying transparence, rgbft
>seems too limiting.

[snip]

>It would allow a separate pigment for the transparence calculations,
and
>would allow one to have an object of one color filter light like an
>object of another color(I believe there are some real-world substances
>which actually do this).

Fluorescent/phosphorescent substances you mean?
e.g. Fluoroscene-sodium.
When this (orange-appearing, but that may be because of light) powder is
dissolved in water the water is green when viewed in shadow, orange if
viewed in the light. Used in high-school physics to demonstrate internal
reflection (fishtank full of green water, except for the orange path
that light took...)

That the sort of thing you were referring to?

Have Fun
Martin
--
<Spa### [at] tesseractcomau> is a valid address
If you prefer mnemonic addresses you can use:
<Martin 'at' tesseract.com.au> or <Martin.Crisp 'at' Tourism.tas.gov.au>

My opinions should not be taken as indicative of Tourism Tasmania's
opinions

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I kind of like this idea.  How exactly would the pattern specity the
trnasparency?  Would you use a transparency_map (or would a color_map or
pigment_map be sufficient)?  This might be adding overkill to the system
and may just confuse people, but I still think it might be a good idea.

One thing to note: You can already create the filter/transmit versions of
this by using a pigment_map.

-Nathan

Chris Huff wrote:
> 
> I have been thinking about a new way of specifying transparence, rgbft
> seems too limiting.
> The new way would look like this:
> 
> New pattern: solid OFFSET//where OFFSET is the point on the color map(or
> whatever map)
> 
> transparence {//this would either go under texture or pigment, probably
> the latter
>     multiplicative PATTERN
>     additive PATTERN
>     subractive PATTERN
>     filter PATTERN
>     transmit PATTERN
> 
>     pigment {}//an optional pigment, if present, this is used for
> transparence calculations
> }
> 
> It would allow a separate pigment for the transparence calculations, and
> would allow one to have an object of one color filter light like an
> object of another color(I believe there are some real-world substances
> which actually do this).
> It would be very useful in layered textures, and would make some very
> interesting surrealistic scenes possible. Also, it might make good
> clouds when used with the layered objects approach.

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The pattern for the transparence attributes(multiplicative, etc)
specifies the amount of transparence at each point(0-1). The pigment is
optional, and if present, will replace the texture pigment in
transparence calculations: give the texture a green pigment, and the
transparence a red one, and you will have red filtering on a green
object.

I don't know if a transparency_map would be necessary. I think
everything could be done without it...maybe it would be a good idea. I
am still not sure where it should go, maybe fade_power and fade_distance
should be moved to transparency, which would go into interior.

An alternative way of doing this would be to allow each transparence
attribute to have it's own pigment. So you could have a transmit from
one pigment, filter from another...Overkill? Probably.

And yes, some uses of the filter/transmit portion could be done with a
pigment_map, but it will only work correctly with layered textures in
your UVPov with layer filtering turned on.

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Yes, I think those may be the substances I was thinking of. I didn't
remember anything about them being phosphorescent or flourescent, but I
seem to now...it has been a long time. Time to go read the encyclopedia.

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Chris Huff wrote:
> 
>     additive PATTERN
>     subractive PATTERN
>     filter PATTERN
>     transmit PATTERN

AFAIK, filter=subtractive and transmit=additive. But there are many other
methods and I'll take them all, thank you :)

Margus

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Not far removed from this topic is something I spoke of a while ago. How
hard would it be to introduce something like color_bleed, so that a specific
colour could be made to bleed onto it's surroundings to give a glow effect.
This and other 'post-processing' type effects would be extremely welcome IMO

Andy

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Yes, I think that is right, and my original idea didn't have filter or
transmit, but I think it would probably be a good idea to have them as
well(for the people converting from older textures, and those who like
the words filter and transmit). They would mean the same thing, and they
could be taken out with no problems. Also, this is nowhere near a
complete list of the kinds of transparency possible.

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Discussion moved to povray.programming

Chris Huff wrote:
> 
> The pattern for the transparence attributes(multiplicative, etc)
> specifies the amount of transparence at each point(0-1). The pigment is
> optional, and if present, will replace the texture pigment in
> transparence calculations: give the texture a green pigment, and the
> transparence a red one, and you will have red filtering on a green
> object.

[etc]

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Andrew Cocker opined:
> Not far removed from this topic is something I spoke of a while ago. How
> hard would it be to introduce something like color_bleed, so that a
specific
> colour could be made to bleed onto it's surroundings to give a glow
effect.
> This and other 'post-processing' type effects would be extremely welcome
IMO

    Well, not to flame, but - if you want post-processing effects, get/use a
post-processing program!  Anything with color-based masking and layers will
give you far, far better bleeds than hanging a bag on the side of POV-Ray
will ever do.

    You know you've been raytracing too long when - you want your entire OS
and all your apps to be part of your raytracer <grin>.

    Seriously, what *would* be nice is a way to get POV-Ray to put out an
additional image with each major object represented by a big flat area of a
distinctive color, to alow precision masking in a post-processing program.
Something in the spirit of those black and white keys they put besides
photographs, with each person/building/animal in outline & numbered.  And -
it's there already! Use quick-color and a very low quality setting :-)

    Also, it would be nice if people didn't feel (as some do) that they had
to apologise for postprocessing. Art is art, and if you have to put the
paint on with your nose to get the right effect, then you do that.

    -Robert Dawson

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