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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Thu, 22 Jan 2004 22:02:08 GMT
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Viewed:
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4287 times
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In lugnet.cad.dev, Don Heyse wrote:
> In lugnet.cad.dev, Steve Bliss wrote:
> > LDraw.org Colour Definition meta-statement
> > ------------------------------------------
> >
> > This meta-statement will specify the properties of a single LDraw
> > colour code. This statement may appear at any time in an LDR file,
> > but will probably be most useful in the file header.
> >
> > Scope. A color definition will affect colors from the point it
> > first appears, continuing through the end of the file. Commands
> > preceding a colour definition will not be affected by the
> > definition. Color definitions will expire at the end of the file in
> > which they appear, effectively going out of scope. Color
> > definitions will be passed to subfiles.
> >
> > The configuration file, ldconfig.ldr, is not affected by the scoping
> > rules, in the sense that the definitions in ldconfig.ldr remain in
> > effect after the renderer is finished processing ldconfig.ldr.
> >
> > 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 #.
>
> I prefer the currently used 0x prefix, but I guess if you picked #
> to match other file formats in use by ldraw users then I can live
> with it. I forget, does POV or HTML use # for the hex prefix?
HTML uses #
> > Byte values are integers in the range 0-255.
> > Identifiers are alphanumeric strings, case-insensitive.
> >
> > Definitions of parameters.
> > name - A short name for the color. Name may be any identifier. This
> > item is provided mainly for human recognition. Name is a required element.
>
> No spaces in the name? Alpha-numeric only? Other constraints?
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.
> > CODE x - The LDraw color code. For LDraw compatibility, x is an
> > integer 0-511. If strict LDraw compatibility is not required, x is
> > any identifier recognized by a rendering program as a color code.
> > Code is a required element.
> >
> > VALUE v - The color value. v is a 24-bit RGB value. VALUE is a
> > required element.
> >
> > 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.
> > 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
> 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
See below
> 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.
>
> > LUMINANCE l - Brightness for colors that glow. l is a byte
> > value. Luminance is not used by LDraw renderers, but may be used
> > for translation to other rendering systems. LUMINANCE is optional.
>
> > Only one of CHROME, METALLIC, RUBBER, and MATERIAL may be
> > specified for a single color. They all specify the finish/texture
> > to be applied to an object being rendered. Other finish-tags may be
> > defined over time.
>
> > CHROME - A flag indicating that surfaces should have a
> > mirror-like finish. Not currently used by LDraw-compatible
> > programs, but may be implemented in the future. CHROME is optional,
> > and may not appear with METALLIC, RUBBER or MATERIAL.
>
> > METALLIC - A flag indicating that surfaces should have a finish
> > like Lego's 'metallic' colors. These colors are commonly called
> > 'pearlescent' by fans. Not currently implemented in
> > LDraw-compatible programs. METALLIC is optional, and may not appear
> > with the CHROME, RUBBER or MATERIAL.
>
> Shouldn't this have an optional color for the embedded bits, or is
> that going to be handled by the DITHER color? I agree with Travis.
> METALLIC is confusing. What's wrong with PEARLY or SPARKLY? Is
> metallic what Lego calls it?
I agree with you, I like PEARLY. When I read metallic, I think smooth metal
finish not the "pearly" finish the spec states. Yes TLC calls the color with
embedded bits Metallis but that doesn't mean we should call it that.
> I'd like to see a predefined METAL tag for rails and electrical
> contacts.
Already in discussion. I brought this up just before Steve posted so it didn't
make it into this draft of the spec
> > RUBBER - A flag indicating that surfaces should have a finish
> > like rubber (typically rubber tubing or rubber tyres). RUBBER is
> > optional, and may not appear with CHROME, METALLIC or MATERIAL.
>
> > MATERIAL [name <params> ...] - Some other surface finish
> > requiring customized parameter(s). Name is an identifier. MATERIAL
> > is not used for official LDraw.org color definitions, it has been
> > made available for use by programs. MATERIAL is optional, and may
> > not appear with CHROME, RUBBER or METALLIC. MATERIAL should be the
> > last tag on the !COLOUR statement.
>
> Do we really want the MATERIAL params on the same line as the color?
> I think we just want the name there. Define the params somewhere
> else. Think about the predefined materials we have now (ABS, RUBBER,
> CHROME...). They come in multiple colors. Define the material once
> and select it by name on the !COLOUR line. Or maybe we want to be
> able to override the params of a previously defined material on the
> !COLOUR line?
Since the official LDraw.org color def don't use this tag, we haven't really
discussed it will be used. Steve?
-Orion
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Message has 2 Replies:
 | | Re: [LSC] Colour Definition meta-statement
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| (...) I won't make any guarantees, but there's a reasonably high probability that I won't even try to support the above, even if it's what the spec says in the end. It's too much of a pain. Additionally, it disallows further expansion of the colour (...) (23 years ago, 22-Jan-04, to lugnet.cad.dev)
| | | Re: [LSC] Colour Definition meta-statement
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| (...) 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 (...) (23 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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| (...) I prefer the currently used 0x prefix, but I guess if you picked # to match other file formats in use by ldraw users then I can live with it. I forget, does POV or HTML use # for the hex prefix? (...) No spaces in the name? Alpha-numeric only? (...) (23 years ago, 22-Jan-04, to lugnet.cad.dev)
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