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Part reviewing tutorial and checklist - Jim DeVona - 2011-08-05

Discussion here has encouraged me to [re]start reviewing parts in the tracker. If you're interested in doing the same, you may not be sure how to start, so I thought I'd share some helpful links and ideas.

Neils Bugge has written a pretty nice comprehensive tutorial about reviewing LDraw parts. He describes what to look for and some good tools to use.

I find it helpful to have a list of specific things to check every time I go through a process like this. Following Neils' example, I think there are two basic types of tests: using various programs to help check for technical errors, and inspecting the part visually to look for more subtle or subjective issues. Here's my checklist:

- Does it look like the physical part? Right type of studs, clips, etc.? Are the dimensions right? (Bricksmith will report real-world dimensions. Other programs will give the bounding box in LDraw units, too.)

- Is the origin and orientation of the part sensible and consistent with similar parts? (Using the "Show Axes" option in LDView or L3Lab is useful for this comparison.)

- Does LDView report any errors or warnings?

- Does L3P report any errors? ("l3p -check PARTFILENAME.dat" )

- Does Planarcheck report any problems? ("planarcheck PARTFILENAME.dat" )

- Inspect with BFC color coding in LDView or L3Lab - are any back (red) surfaces visible?

- Check for proper stud orientation by rendering with L3P or enabling stud logos in LDView.

- Check for appropriate coordinate precision and number format (leading/trailing zeros, etc. See spec.)

- Does the part make use of relevant primitives (stud groups, boxes, clips, pins, etc.)? (Note my opinion that if everything else listed above checks out, it should be OK to certify a part even if could still be refactored for better efficiency or performance. As Willy points out in reply, this is what the "needs work" label is for. I think it's important to utilize this option to get new parts out to users promptly.)

I encourage more experienced part reviewers to chime in with additional advice. Note that I've only included Mac-compatible software in my list - as Neils' tutorial mentions, Windows users will want to employ MLCad and LDDP.

Last but not least, to review parts you need to get reviewer privileges for your LDraw.org account. Hopefully someone can explain that process as well - it seems a bit like a "you need to know somebody who knows somebody" process, if I recall correctly.


some remarks - Steffen - 2011-08-06

I'd like to just add some remarks which have sped up my reviewing process and might also be wanted be others.

(a)
As I'm on Windows, I have added an entry to the registry which allows
me to invoke l3p for *.dat and *.ldr files with its -check option
via right mouse click context menu.

(b)
LDView can be customized, so that the button for turning on and off the origin display
is in the main window toolbar. In fact, the origin display is on for me by default.
Once you have looked at it some times, you miss it when it is turned off.

©
Another thing I do when checking is:
I have added the "set random colors" button to LDView's main toolbar.
I switch to that mode and then move the file in 3D view a little.
This reveals overlapping quads, which normally should be avoided.
If they are of the same color, this can be given as a hint to a user.
However, that flaw is small and IMHO not worth holding a part up.
Different is the situation when the quads are of different color.
Then that is a HOLD.

(d)
Checking for correct logo orientation can be done much quicker if you add these lines:

to stud.dat:
1 16 0 -4 0 0 0 -1 0 1 0 1 0 0 logo.dat

to stud2.dat:
1 16 0 0 0 0 0 -.6 0 1 0 .6 0 0 logo.dat

and then add this file into your P folder:

0 LEGO Logo for Studs
0 Name: logo.dat
0 Author: Paul Easter
0 !LDRAW_ORG Unofficial_Primitive

0 BFC CERTIFY CCW

0 !HISTORY 2000-11-05 [Paul Easter] corrected "E"
0 !HISTORY 2011-01-24 [Steffen] polished header

2 24 -4 0 2 -5 0 -2
2 24 -5 0 -2 -3.5 0 -2
2 24 0 0 2 -2 0 2
2 24 -2 0 2 -3 0 -2
2 24 -3 0 -2 -1 0 -2
2 24 -1 0 0 -2.5 0 0
2 24 2.25 0 1.5 2 0 2
2 24 2 0 2 1 0 2
2 24 1 0 2 .5 0 1.5
2 24 .5 0 1.5 -.25 0 -1.5
2 24 -.25 0 -1.5 0 0 -2
2 24 0 0 -2 1 0 -2
2 24 1 0 -2 1.5 0 -1.5
2 24 1.5 0 -1.5 2 0 0
2 24 2 0 0 1 0 0
2 24 4.75 0 1.5 4.5 0 2
2 24 4.5 0 2 3.5 0 2
2 24 3.5 0 2 3 0 1.5
2 24 3 0 1.5 2.25 0 -1.5
2 24 2.25 0 -1.5 2.5 0 -2
2 24 2.5 0 -2 3.5 0 -2
2 24 3.5 0 -2 4 0 -1.5
2 24 4 0 -1.5 4.75 0 1.5

After you have done that, the logo will be visible in all programs, like MLCad, L3Lab, LDView (without primitives substitution).
Here it is the same: once you've looked at this several times, you miss the logo in MLCad
when it is not there ;-)


don't forget to also check correct color usage - Steffen - 2011-08-06

don't forget to check proper color usage:

- in files which are not physical color shortcuts: is color 16 used correctly?
- do edges have color 24 where required? (is also checked by L3P, LDView)

more difficult is:

- there are special colors for rubber. people sometimes use the wrong ones for that, i.e., the normal plastic material colors (e.g. "black" vs. "rubber black" )

- a very difficult question is the proper use of silver color, see this thread: http://forums.ldraw.org/showthread.php?tid=214&pid=214#pid214


Re: Part reviewing tutorial and checklist - Orion Pobursky - 2011-08-06

You might also run the part through DATHeader. This is the modern day L3P -check. It definitely checks more things than L3P or LDDP. Unfortunately, according to Michael, it may not be Mono compatible any more so Windows only, no Mac/Linux.