LDCad shadow library / parts snapping questions

[LDCad] shadow library / parts snapping questions - Printable Version

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shadow library / parts snapping questions - Basil Bader - 2023-08-05

I have a few questions about the LDCad shadow library and the snap metas:

1. Grid with 6 parameters
I found this line in 71861.dat:

Code:
0 !LDCAD SNAP_CYL [gender=M] [caps=none] [secs=R 2.5 5] [center=true] [ori=0 1 0 0 0 -1 -1 0 0] [grid=1 C 2 1 0 46 0]

According to the docs, Xcnt would be 1 and Zcnt C 2. After that, there are still four numbers left (1 0 46 0), but there should only be two.
In LDCad the cylinders are moved in the Y-direction (along the axis of the cylinders), but I did not find any documentation about this. What does this additional parameter mean exactly? Is there an undocumented alternative [Xcnt Ycnt Zcnt Xstep Ystep Zstep] format?

2. Default of SNAP_FGR.center
According to the docs, SNAP_FGR.center is the same as SNAP_CYL.center. There, the default is false. But in LDCad it seems like the default of SNAP_FGR.center is true. Which is correct?

3. Matching of SNAP_GEN bounding shapes
How are SNAP_GEN bounding shapes matched? do they only match when they are the same type? In which cases does the orientation matter? How the groups work is clear, but the docs are very vague about the rest.

4.SNAP_CYL.mirror.cor
According to the docs, one of the radius axes must be flipped if the transformation matrix contains a mirroring and SNAP_CYL.mirror is set to "cor". How does that work exactly? Flipping a cylinder on any axis doesn't change its shape.

Thanks in advance for answering and have a nice day!

RE: shadow library / parts snapping questions - Roland Melkert - 2023-08-05

(2023-08-05, 0:17)Basil Bader Wrote: 1. Grid with 6 parameters

The sequence is:
C x C z StepX stepZ
or
C x C y C z stepX stepY stepZ

The C's are optional indicating if the grid is centered on the corrisponging axis.
The documentation was written before the longer variant was added,

(2023-08-05, 0:17)Basil Bader Wrote: 2. Default of SNAP_FGR.center

Both are true fgr is centered by default cyl not.

(2023-08-05, 0:17)Basil Bader Wrote: 3. Matching of SNAP_GEN bounding shapes

They are matched on group, shape and size depending the match setting. if it is set to shape (def) it will match on group and shape, if it's on group just the groups needs to match.
The placement option is applied when possible.
Retain means it will snap in the current orientation of the dragged part.

(2023-08-05, 0:17)Basil Bader Wrote: 4.SNAP_CYL.mirror.cor

If the option is set to cor and a mirrored matrix is detected during inheritance it will try to corrected this by flipping x or z.
Like you wrote this is invisible for cylinders but it prevents mirroring parts when they snap to it.

RE: shadow library / parts snapping questions - Basil Bader - 2023-08-07

Hi Roland
Thank you very much for your clear and helpful answer!
The LDCad Shadow Library is very useful and I will submit some PRs if I find time to improve it.