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Chain links 3711 / treads 3873 |
Posted by: Sylvain Sauvage - 2022-07-25, 20:07 - Forum: General LDraw.org Discussion
- Replies (5)
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Hi all,
3711/3873 both have a span (distance between connectors) of 16LDU.
IRL, the distance is slightly bigger. It’s about 2.7% more. (Measured while digital-building 10303: it needs 262 links in digital, while 255 (222+33) are in the set / instructions.)
That would make a span of about 16.4LDU.
So, two questions:
1. Am I the only one bothered with that? I.e. not having the correct number of parts in digital builds.
2. Could it be changed? Or is there a rule (that I didn’t find) somewhere saying that it can’t?
I mean, excluding backward compatibility rules. So to rephrase the question: Could a similar part be built & officialized with a span of 16.4LDU?
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Advanced rotation techniques |
Posted by: N. W. Perry - 2022-07-22, 13:40 - Forum: LDraw Editors and Viewers
- Replies (12)
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I feel like I'm under-using LDCad's advanced rotation capabilities. But instead of a question, I think it's easier to just give an example—and sort of a challenge. 
In the attached test file I have an oddly-shaped piece that I want to rest on the ground, here represented by a nice big tile. This part has four lower extremities, all with different y-values, and to be realistic it would need to rest against the lowest three of them. What's the best way to do this using LDCad?
test.ldr (Size: 173 bytes / Downloads: 2)
Here's how I would approach it:
- Find the lowest point and set it as the rotation center. You could use a helper part or a marker, but how do you find the point itself? Easiest way would be if you could directly select the vertex—LDCad can't do this, but LDPE can.
- Find the next lowest point the same way, then using more helper parts and some trigonometry (or the handy, but unofficial, right angle calc script), rotate the part so this hits the ground.
- For the final rotation, select the third low point, and rotate around a vector formed by the first two points. LDCad does allow custom vector rotation—but how do I find the vector and enter it into the rotation dialog?
Even better would be if you could select all three points at once and use them to define a plane, then set the part's absolute rotation just once so that this plane matches the ground plane. This could probably be scripted, but there's still the problem of selecting the points in the first place.
Is there a better way? How would you approach this problem?
(Can't attach the .lua file for the angle script, but here it is
Code: function onRun()
local sel=ldc.selection()
if sel:getRefCount()<3 then
return
end
local a=sel:getRef(1):getPos()
local b=sel:getRef(2):getPos()
local c=sel:getRef(3):getPos()
local ba=a-b
local bc=c-b
local n=bc:getCross(ba)
n:normalize()
local bb1=n:getSignedAngle(ba, bc)
local bb2=math.deg(math.acos(bc:getLength()/ba:getLength()))
local angle=-(bb1-bb2)
ldc.setClipboardText(angle)
ldc.dialog.runMessage(angle)
end
function register()
local macro=ldc.macro('Right angle rotation calc')
macro:setEvent('run', 'onRun')
end
register()
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