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Subject: 
Re: MPD format
Newsgroups: 
lugnet.cad.dev
Date: 
Tue, 16 Mar 1999 07:24:08 GMT
Viewed: 
736 times
  
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.

If valid drawing lines are encountered first, well, here's an example
of what might happen:

Let's say I have two MPD files:
MPD1.DAT:
1 1 0 0 0 1 0 0 0 1 0 0 0 1 3001.dat
0 FILE top.dat
1 16 0 -24 0 1 0 0 0 1 0 0 0 1 mpd2.dat

and

MPD2.DAT
1 4 0 0 0 1 0 0 0 1 0 0 0 1 3001.dat
0 FILE five.dat
1 5 0 -24 0 1 0 0 0 1 0 0 0 1 3001.dat

Lars, What gets rendered from "L3P MPD1.DAT"?
(Forgive me for not just trying this, mostly
I want to know what you think should happen,
not what actually does).

LDLite will do the following, just by its nature:
Draw a 3001 in color 1
Load top.dat into cache
clear the screen
draw a 3001 in color 4, offset by -24
load five.dat into cache
clear the screen
draw a 3001 in color 5 offset by -24 (not by -48, since it
starts over at the beginning of five.dat)

IMO, LDLite should do the following:
Draw a 3001 in color 1
Complain, but Load top.dat into cache anyways.

To explain further: if there are valid drawing lines before "0 FILE"
is encountered, drawing should not start over with the first subfile.
Also, in LDLite, those first valid lines cannot refer to the subfiles
since the "0 FILE" statements have not yet been encountered.

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

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.
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.
-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
 
On Tue, 16 Mar 1999 07:24:08 GMT, Paul Gyugyi <paul@gyugyi.com> wrote: [snip] Just a short post, to say "I agree!" Steve (26 years ago, 16-Mar-99, to lugnet.cad.dev)

Message is in Reply To:
  Re: MPD format
 
(...) 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 (...) (26 years ago, 15-Mar-99, to lugnet.cad.dev)

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