Subject:
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Re: [LSC] Colour Definition meta-statement
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Newsgroups:
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lugnet.cad.dev
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Date:
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Fri, 23 Jan 2004 15:14:22 GMT
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Viewed:
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1918 times
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In lugnet.cad.dev, Orion Pobursky wrote:
> In lugnet.cad.dev, Don Heyse wrote:
> > In lugnet.cad.dev, Steve Bliss wrote:
> > > LDraw.org Colour Definition meta-statement
> > > Syntax. The entire statement must appear on one line. It's broken into
> > > two lines in this definition for clarity.
> > > 0 !COLOUR name CODE x VALUE v EDGE e [ALPHA a] [DITHER d]
> > > [LUMINANCE l] [CHROME | METALLIC | RUBBER | MATERIAL <params>]
> > >
> > > Tags. CODE, VALUE, EDGE, ALPHA, DITHER, LUMINANCE, CHROME,
> > > METALLIC, RUBBER and MATERIAL are keyword tags. Some tags are
> > > followed by a single parameter value. Tags are case-insensitive.
> > >
> > > Numeric parameters may be specified in decimal or hexidecimal.
> > > Hexidecimal values must be prefixed with #.
> > >
> > > EDGE e - The contrasting edge color. e may be either a color
> > > code or an RGB value. EDGE is a required element.
> > >
> > > ALPHA a - The alpha channel (transparency) value. a is a byte
> > > value, where 0 is totally colorless and #FF is completely opaque.
> > > LDraw programs that use dither-transparency recognize values 1-127
> > > as transparent, and 128-255 as opaque. A 0 value is totally
> > > colorless (useful for temporarily hiding sections of models). ALPHA
> > > is an optional element.
> >
> > Does the alpha value only apply to the VALUE color, or does it also
> > apply to the EDGE, DITHER colors? I'm not sure what you mean about
> > the dither-transparency. Nobody supports this format yet, so why
> > are we concerned about special meanings for old programs?
>
> ALPHA should apply to the VALUE color and the color provided by any
> DITHER tag.
But what if Lego prints an opaque dithered pattern on a transparent
brick? I think the ALPHA is more versatile if only applied to the
VALUE color. You can still get an alpha dither color by using a
color code for d which points to a color with an alpha setting.
> > > DITHER d - Specifies the color should be dithered, and provides
> > > the second color value. d may be either a color code or an RGB
> > > value. DITHER is optional.
> >
> > Are you thinking about original LDRAW compatibility here
>
> Yes
Why? What program are you thinking of that'll read this new
metacommand and yet still draw dithered colors? Any new program
should be able to figure out how to convert a single RGB to a
pair of dithered colors if it has to. If anyone needs it, Leo
provided the code for this in ldglite a long time ago. It's used
to generate the 256 color BMP file screen shots.
If you're planning on using the DITHER tag to explicitly break up a
single color into two dithered components for some nonexistant program,
how can I tell the difference between that and a DITHER tag used to
describe something real, like a dithered paint job? Look closely at
the print on the front and back of the stormtrooper torso to see what
I mean.
> > or about future needs? I see this as a good way to represent dithered
> > printing like on the 6190 aquashark baseplate, and perhaps to provide
> > a separate color for the embedded bits in the pearly bricks
> > but not much else. I sort of wish the DITHER and EDGE colors had their own
> > ALPHA and LUMINANCE values, but I suppose you can use a color code to
> > pull that in.
I think we're getting close. If we can patch up these last few
issues, it should be workable.
Don
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Message has 1 Reply:
 | | Re: [LSC] Colour Definition meta-statement
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| (...) I've been keeping clear on the dither issue so far, because I didn't have a strong opinion one way or another. However, the more I think about it, the more I think we're not seeing the forest through the trees. Because of this, I vote we (...) (20 years ago, 23-Jan-04, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: [LSC] Colour Definition meta-statement
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| (...) HTML uses # (...) The name should be the characters after the !COLOR keyword and before the next keyword. The only contraint I can think of is that is not be one of the other keywords. (...) ALPHA should apply to the VALUE color and the color (...) (20 years ago, 22-Jan-04, to lugnet.cad.dev)
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