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Subject: 
Re: MPD format
Newsgroups: 
lugnet.cad.dev
Date: 
Tue, 16 Mar 1999 09:50:47 GMT
Viewed: 
724 times
  
Paul Gyugyi wrote:
I think valid drawing lines before the first "0 FILE" of an MPD file
should not be allowed (comments and garbage lines are OK).  Either
it is an MPD file, or it is not.

Yes, I agree.
But MPD is not very parser-friendly. You read the file and half-way
down it says: "Oh, by the way, I'm an MPD!"

How are you supposed to avoid complaining about garbage lines before
the first "0 FILE" without parsing each file twice?

Lars, What gets rendered from "L3P MPD1.DAT"?

Since there are errors in the MPD files, I think that the result
should be undefined :-)

I think MPD file can be useful when included in Type 1 lines.
If the files were instead defined as:
MPD3.DAT:
1 3 0 0 0 1 0 0 0 1 0 0 0 1 3001.dat
1 16 0 -24 0 1 0 0 0 1 0 0 0 1 mpd4.dat

MPD4.DAT:
0 FILE four.dat
1 4 0 0 0 1 0 0 0 1 0 0 0 1 3001.dat
1 16 0 -24 0 1 0 0 0 1 0 0 0 1 five.dat
0 FILE five.dat
1 5 0 -24 0 1 0 0 0 1 0 0 0 1 3001.dat

Then I think LDLite should:
Draw a 3001 in color 3 at offset 0
Draw a 3001 in color 4 at offset -24
Draw a 3001 in color 5 at offset -48

Yes.

To further clarify, a Type-1 include of an MPD file (with no valid
drawing lines before the "0 FILE") should be translated into a
Type-1 include of the first subfile of the MPD file.  This would
avoid the need for a sub-parts directory, since sub-parts could be
included in the MPD file.

Yes, this is a very good thing. It keeps all related files of a part
in a single file.

If things work that way, we would also need your meta command
"0 LOADCACHE parts.dat" to load part libraries in without drawing the
first subfile.

Go ahead, if you feel the need for loading part libraries. In my L3
project I just retain parts in memory once loaded. I wouldn't waste
time on preloading parts no-one needs.
/Lars

-gyug

"Lars C. Hassing" wrote:

Paul Gyugyi wrote:
By convention, tools like L3P and LDLite, when given an mpd
file, will render the first subfile.  The subfiles can reference
each other.

If you use an MPD file in a Type 1 line, your results will vary.
LDLite will (I think) finish drawing the top-level file, and then
start over drawing the first subfile of the last MPD file
encountered.

L3P will treat an MPD file in a Type 1 line exactly as it treats
an MPD file as the main file (top-level file). L3P's nature is
recursive.
An MPD file is just another way of storing sub-files.
In stead of loading sub-files from the usual directories, some
sub-files are simply taken from the MPD file.

I will be changing this.  In version 1.7, having a type-1 • line that
specifies an MPD file will not draw anything, but just • load all the
parts into memory so they can be used later in the file.  This
would allow you to convert the PARTS directory to a • single MPD file,
and then specify "1 16 0 0 0 1 0 0 0 1 0 0 0 1 parts.dat" in your
start-up file.

In stead of changing the well-known semantics of
"1 16 0 0 0 1 0 0 0 1 0 0 0 1 parts.dat"
to depend on the contents of parts.dat, wouldn't it be better to
use a META command? Like "0 LOADCACHE parts.dat"
/Lars




Message has 1 Reply:
  Re: MPD format
 
(...) I'm thinking of the case where foo.dat only appears in the MPD file fooarchive.dat, such as would happen if someone replaced the whole P directory with a single MPD file to save disk space, or if I chose to distribute my unofficial Throwbot (...) (26 years ago, 17-Mar-99, to lugnet.cad.dev)

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