SylvainLS

More up-to-date ldraw.xml LDD/LDraw conversion file

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I propose to keep here an up-to-date ldraw.xml, the file used by LDD to convert to and from LDraw files.

Download: latest version

On Windows: download  and replace the one in “C:\Program Files\LEGO Company\LEGO Digital Designer\”

On Mac: download and replace the one in the “Contents\Resources\” folder in the app (open “Applications” in Finder, right click on the “LEGO Digital Designer” package and select the “Show Package Contents” option to explore the pakage folders). (Thanks manglegrat!)

If you have other modifications or additions, post them here or send me a personal message and I’ll include them to the benefit of all.

If you need a part, feel free to ask here and I’ll try to add it (provided it exists in LDraw and LDD).

History and Contents

  • It’s based upon gallaghersart’s latest version (see this thread).
  • It includes the modifications shutterfreak published in his thread.
  • It uses some of the LDraw unofficial parts (mainly for new parts in LDD Brick version 2075).
  • It includes some name corrections (because LDraw renamed or moved some parts, added new variants, etc.).
  • I tried to more accurately convert the colors (now mainly according to Ryan Howerter’s conversion table). It’s not easy because all sources (Swooshable, Mecabricks, Ryan) don’t agree, and there are holes and overlaps. But as these differences, holes, and overlaps occur for rare colors or colors that aren’t available in LDD, it should be okay.
  • In a megalomaniacal way, all the entries I have modified have an “SLS” at the end of their heading comments. New entries have an “SLS” at the front of the comments.
    So it’s easy to know when to blame me.
    As of 2016-09-16 and the big overhaul, I assume all the errors.

Know Limitations

  • As of LDD 4.3.9, flex parts (hoses) are not exported anymore (even unflexed).
  • Minifig arms and hands are not connected in LDraw. I don’t know whose geometry is off (both?) but the shapes differ a lot. At least, hands are correctly connected to whatever they clip and arms are correctly placed in their sockets and somewhat wrap around the hands’s stems.
  • Some variants are not recognized by LDD (e.g. clips, or tiles with/without groove, etc.) In those cases, I prefer to use the most recent variant in LDraw as it generally is easier to find and cheaper.
  • Sometimes, several LDD parts correspond to a unique LDraw part. Sometimes, the transformation is accurate for one variant but not for another. For example, the Flag 2 x 2 is known to LDD as 2335, 11055, and 60779, but LDraw only has the 2335 variant. 2335 and 60779 use the same transformation but 11055 is vertically offset. I preferred to badly convert 11055 to 2335 rather than not convert it at all or badly convert 2335 and 60779.
  • ldraw.xml is used both ways (LDD to/from LDraw). It’s not something I do frequently (too many resulting collisions) so it’s not well tested. One problem I can see is that, when several LDD parts correspond to a unique LDraw part, the conversion that’s listed last is the one that will be used. The reverse (first written is the one used) is true for assemblies that use the same subparts, in the same quantity (like electric cables).
  • A lot of LDraw parts are simply wrong. Almost all the parts that combine System (studs and anti-studs) and Technic (pins and axles, and their holes) are wrong in that they assume the technic holes are at the same height than side studs (on the picture below, the circles are concentric).
    ldr_concentric.png
    LDD assumes the holes are 0.2 mm (0.5 LDU) higher.
    In ABS, the holes are 0.12 mm (0.375 LDU) higher (dixit Jamie Berard in his famous presentation). In order to limit the number and magnitude of errors, LDD is considered to be right.

How to write a new transformation for a part in ldraw.xml

What?

ldraw.xml is an XML file that defines how LDD can export to (or import from) LDraw files.

It does so by defining a match between the part’s IDs and how to rotate and translate the part from one geometry to the other.

Matches are defined by “Brick” XML elements.

For example, this one says to LDD that the Brick 1x1 that it knows as 3005 is also known to LDraw as 3005:

<Brick ldraw="3005.dat" lego="3005" />
 

(Note the “.dat” in the ldraw ID.)

Matches are not needed if the part IDs are the same: the transformation element is sufficient for LDD to know the part exists. (So the example above is useless :grin: )

Rotations and translations are defined by “Transformation” XML elements.

This one says to LDD that the Brick 1x1 just needs to be moved up:

<Transformation ldraw="3005.dat" tx="0" ty="-.96" tz="0" ax="1" ay="0" az="0" angle="0" />
 

The translation (tx, ty, and tz) is in centimeters (0.8 cm is the width of a brick, 0.96 cm its height).

The rotation is given by its axis (the line passing through and ), and its angle in radians.

And all the coordinates are in the direct (“riht-handed”), Y points up, coordinates system of LDD.

The transformation explains what should be done to import from LDraw besides changing the axes (LDD’s Y is up and XYZ is a direct basis, LDraw’s Y is down and XYZ is an indirect basis; so changing the axes only means changing the sign of Y).

So, in an LDD to LDraw point of view, the transformation is reversed: it says what happens to a part if you don’t do anything to its coordinates besides changing the sign of Y. In other words, the opposite transformation has to be applied to the LDD coordinates of the part in order to get the LDraw coordinates (with Y reversed).

Why?

Each part has an orientation (which way up? which way left?) and a center, point of origin, or reference point (we’ll use “reference point” from now on).

But LDD and LDraw don’t always agree.

To know the orientation and reference point in LDD, insert the part without rotating it nor attaching it to any other part. It will be aligned along the scene’s axes (LDD’s axes). The reference point is near the mouse pointer’s head.
To know the orientation and reference point in LDraw, I find LeoCAD the easiest tool: just select the part and its axes are drawn (X red, Y green, Z blue), starting at its reference point. Okay, LeoCAD’s «X, Y, Z» is LDraw’s «X, -Z, Y» but what’s another little change of basis? :grin:

Sometimes, their disagreement is trivial.

For example, for the simple 1x1 brick (3005), both LDD and LDraw agree: the stud is on top and the reference point is on the vertical line going through the center of the stud. But they differ for the height at which the reference point should be: LDD says it’s at the base of the brick, LDraw at its top (but at the base of the stud).

howto_1x1_refs.png

(On every picture, X will be red, Y green, and Z blue.)

So the transformation for that part is straightforward: if the LDraw part is imported as is, with only Y reversed, it will end up 0.96 cm (the height of the brick) higher than it should. So we have to lower it by 0.96 cm:

<Transformation ldraw="3005.dat" tx="0" ty="-.96" tz="0" ax="1" ay="0" az="0" angle="0" />
 

Sometimes, their disagreement is more profound and the transformation is therefore more complicated.

For example, for the musket (Minifig Gun Musket 2561), LDD puts the reference point in the handle and “up” means the handle is vertical but LDraw puts the reference point in the barrel and “up” means the barrel is vertical. Even more, the stock is on the wrong side, so X and Z are different too.

howto_musket_comp.png

With an identity transformation, the part is rotated by an eighth of a turn (X to Y) (π/4) around the Z axis to put the barrel vertical, and then by a quarter turn (X to Z) (-π/2) around the Y axis. After that, it has been translated up and horizontally.

After calculations (see below), we’ll end up with this transformation:

<Transformation ldraw="2561.dat" tx="0" ty="-1.72" tz="0.336" ax="-0.3574067443365933" ay="-0.8628562094610169" az="0.3574067443365933" angle="1.7177715174584016"/>
 

How?

So, how do we find the right values to have the correct transformations?

What’s the ID? Having the right part

Check the ID of the part in LDD.

Check the ID of the part in LDraw.

Beware of variants, LDraw uses a letter suffix (a, b, c…) where LDD totally changes the ID or keeps the same ID for new variants.

Don’t hesitate to look on BrickLink for the part ID: BrickLink keeps a list of alternate IDs (when the same part has several IDs) and links to variants and notes.

If the IDs are the same. Nothing to do.

If the IDs differ. We add a Brick element:

<Brick ldraw="123a.dat" lego="456" />
 

Don’t forget the “.dat”!

That was the easy part.

Which way is up? Finding the rotation axis and angle

We start in LDD.

Up is Y, or Y is up.

X and Z are a bit harder to see on the LDD scene unless you use LDD’s developper mode (which has the LDD axes drawn at «0,0,0» as red X, green Y, and blue Z lines). Or, if you’re sure you didn’t move the camera in a brand new model/file, X is pointing bottom right, and Z bottom left.

We place our part among other parts that we know will be correctly converted (like 1x1 plates, or harpoons :grin:) to have references. Using different colors greatly helps!

We export to LDraw…

… and look at the results:

howto_musket_comp.png

We decompose the transformation in multiple simple rotations, around the X, Y, or Z axis.

  • If it has been turned around X, a quarter turn from Y to Z is a positive π/2 angle.
  • If it has been turned around Z, a quarter turn from X to Y is a positive π/2 angle.
  • If it has been turned around Y, a quarter turn from Z to X is a positive π/2 angle.

To make it short, it’s a direct (right-handed) basis.

If you can’t figure out the problems with an existing transformation, “clear” it by using an identity transformation:
<transformation tx="0" ty="0 tz="0" ax="0" ay="1" az="0 angle="0"/>
 
(All zeroes but one of the a_ which is 1.)

You can try each simple rotation one by one to be sure of their angles (especially their signs :wink:).

Beware, combining rotations change their axes (e.g. turning around first X then Y is equivalent to turning around first Y then Z). So if you check that the Y rotation is okay, then the X rotation, don’t forget to combine them as Y then Z.

For the musket, we need two rotations: an eighth of a turn (π/4, 45°) around the Z (blue) axis that puts the barrel vertical, and then a quarter turn (-π/2, -90°) around the Y (green) axis. Or we can first make the quarter turn (-π/2, -90°) around the Y (green) axis, and then an eighth of a turn (π/4, 45°) around the X (red) axis.

howto_musket_comp.png

Remember, “import”-wise, we’re trying to find what should happen to the part in the LDD scene to be like the LDraw one, with the LDD axes (the harpoons :wink:).

My head is turning. Combining rotations

If more than one simple rotation is needed, we have to combine them.

For that, we’ll use quaternions.

Eh come back! That’s not that difficult!

A quaternion q can be written as q = a + b.i + c.j + d.k, where i² = j² = k² = i.j.k = -1 (so i.j = k = -j.i, j.k = i = -k.j, k.i = j = -i.k).

a is the real part, b.i + c.j + d.k is the imaginary part.

A rotation by the angle angle around the axis «ax, ay, az» is the quaternion q = cos(angle/2) + sin(angle/2).(ax.i + ay.j + az.k)

Do note the 1/2 factor on the angle!

To combine two rotations, we just multiply their quaternions and apply the rules above to end up with a a + b.i + c.j + d.k form (or, more accurately, a C + S.(ax.i + ay.j + az.k) form, where C and S are cosine and sine of the same angle and ax² + ay² + az² = 1 ).

If we rotate first by q and then by p, the result is the rotation by p.q.

Note the order: q then p is p.q. Multiplication is not commutative with quaternions: if you do it the wrong way, you’ll end up with the correct values but the wrong signs.

There’re lots of fun to have with quaternions and rotations as quaternions. But what is said here is sufficient for our purposes.

An example:

Most of the times, we do π/2 rotations (quarter turns, 90°).

angle = π/2 therefore cos(angle/2) = sin(angle/2) = cos(π/4) = sin(π/4) = √2/2;

So, for a “horizontal” quarter turn (yaw, around Y): q = √2/2 + √2/2.j (as j/Y is the “vertical” axis).

Let’s combine it with a half turn (π, 180°) around the X axis (IOW, upside-down):

cos(π/2) = 0, sin(π/2) = 1, so p = 0 + i

p.q = (0 + i) . (√2/2 + √2/2 j) = √2/2 i + √2/2 i.j = 0 + √2/2 ( i + k )

Now, let’s get the resulting angle:

The real part of p.q, 0, is the cosine of angle/2.

0 is also the cosine of ±π/2 (±90°).

Therefore, the resulting angle is π (180°).

Now the axis, «ax, ay, az»:

It’s the √2/2( i + k) imaginary part. That’s the vector «√2/2, 0, √2/2».

We need to remove the sin(angle/2) factor. That’s easy as the sine of π/2 is 1.

So our axis is «ax = √2/2, ay = 0, az = √2/2».

Written in ldraw.xml:

ax="0.707…" ay="0" az="0.707…" angle="3.1415…"
 

Another one, a quarter turn around Y and then around X:

q = √2/2 + √2/2 j = √2/2 (1 + j)

p = √2/2 + √2/2 i = √2/2 (1 + i)

p.q = 1/2 (1 + i) (1 + j) = 1/2 + 1/2 (i + j + k)

We rewrite it as p.q = 1/2 + √3/2 (√⅓ i + √⅓ j + √⅓ k) to have a unit vector (ax² + ay² + az² = 1) in the parenthesis and to clarify the cosine and sine: 1/2 and √3/2.

They are the sine and cosine of π/3 (60°).

Therefore, the resulting angle is 2π/3 (120°).

In ldraw.xml:

ax="0.577…" ay="0.577…" az="0.577…" angle="2.094…"
 

Back to our musket:

An eighth of a turn (π/4, 45°) around the Z axis that puts the barrel vertical: q = cos(π/8) + sin(π/8).i = C + S.k

Then a quarter turn (-π/2, -90°) around the Y axis: p = cos(-π/4) + sin(-π/4).j = √2/2 (1 - j)

p.q = √2/2.(1 - j)(C + S.k) = √2/2.(C - S.j.k - C.j + S.k) = √2/2.C + (-√2/2.S.i - √2/2.C.j + √2/2.S.k)

Wow! Hum, okay. So √2/2.cos(-π/8) is the cosine of half our angle. Get the calculator out…

angle/2 = Acos(√2/2.cos(-π/8)) = 0.8589

Our angle is 1.7178.

We “remove” the sine of angle/2 from our vector, so that p.q = cos(angle/2) + sin(angle/2).(ax.i + ay.j + az.k):

ax = -√2/2.sin(-π/8) / sin(0.8589) = -0.3574

ay = -√2/2.cos(-π/8) / sin(0.8589) = -0.8629

az = √2/2.sin(-π/8) / sin(0.8589) = 0.3574

As an exercise, you can verify that ax² + ay² + az² = 1. So we did it right! :grin:

Et voilà:

ax="-0.3574067443365933" ay="-0.8628562094610169" az="0.3574067443365933" angle="1.7177715174584016"
 

howto_musket_rot.png

One step to the left. Getting the translation right

Now that the part is correctly oriented, it may need to be moved.

The translation is in centimeters (cm). 20 LDU = 0.8 cm.

Values are often multiples of 0.4 (half a stud) for tx and tz and multiples of 0.32 (height of a plate) for ty.

Other, finer, tunings are often in multiples of 0.008.

If the rotation is complex, all bets are off :grin:

In LDD, we try to place the part so that its LDraw up axis ends up up in the scene, and we try to align its LDraw X and Z axes with X and Z of the scene (at least, that it is not rotated by a weird angle).

That way, moving the part along its axes is also moving the part along the scene’s axes. It will be easier for getting the translation right.

For our musket, that means the barrel up. (I didn’t align the X and Z axes here because, yeah, I’m a warrior, I don’t need that. Besides, you’ll see what happens because of that. :wink:)

Again, I find it easier in LeoCAD: the key bindings, the coordinates clearly shown in the status bar, etc. The thing is, LeoCAD uses a direct Z up basis. So if you move «dx, dy, dz» in LeoCAD, you’re moving «dx, -dz, dy» in LDD (and vice versa). Confusing? Noooh. :grin:

Anyway, choose your own poison but beware of its little quirks.

To help fine tuning, using transparent colors greatly helps, especially for clip-bar connections.

howto_musket_trans.png

Now, we note the coordinates of our part in our LDraw editor and move it so that it ends up the way it should. We look how much we moved it. That’s it! Just convert it to cm (= LDU × 0.8 / 20) and we have our translation. Well, mostly, the signs are wrong. Remember: the transformation is what should happen to the LDD part to end up like the LDraw part, we just did the opposite and moved the LDraw part to be like the LDD one.

Besides the signs, if you didn’t correctly align the axes, you’ll have to find which is which :grin:

For our musket, we need to go up and sligthly to the “left” (from bottom right to upper left when your LDraw view is oriented as a new LDD file, as are all the screenshots here). That means negative dy and dx. But as the part is not aligned on X and Z (but still not badly rotated), the negative dx becomes a positive dz.

Et voilà!

howto_musket_okay.png

<Transformation ldraw="2561.dat" tx="0" ty="-1.72" tz="0.336" ax="-0.3574067443365933" ay="-0.8628562094610169" az="0.3574067443365933" angle="1.7177715174584016"/>
 

(So, okay. I had to try first tx then tz, both negative and positive, before I found the right one. But I didn’t want to have to remake the pictures! There: I’m not a warrior, I’m just lazy.)

Edited by SylvainLS
Mac usage

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Update 2016-07-11

Download link in the first post.

Corrected:

  • 4697 / 4697b.dat Technic Pneumatic T-Piece Type 2
  • 30194 / 30194.dat Minifig Circular Blade Saw
  • 33183 / 33183.dat Minifig Food Carrot Top

Edited by SylvainLS

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Somehow Ldraw topics are doing very bad on google search. Pretty much any time I searched for something (for example up-to-date ldraw.xml), everythng pointed to the Ldraw homepage.

Maybe I use wrong keywords or I should just join the ldraw forum.

BTW, how does one earn the LDD builder badge?

Edited by Lipko

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20 tooth double bevel appears to need the following addition:

<!-- Technic Gear 20 Tooth Double Bevel 32269.dat 17 -->

<Brick ldraw="32269.dat" lego="18575" />

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Someone please let me know if I'm doing this correctly or not by posting here.

  • Power Functions Large Motor
  • Power Functions Servo Motor
  • Power Function AAA Battery Box

<!-- Electric Power Functions Large Motor 99499 18 -->

<Brick ldraw="99499.dat" lego="10089" />

<Transformation ldraw="99499.dat" tx="1.2" ty="-0.8" tz="-0.4" ax="0" ay="1" az="0" angle="1.570796"/>

<!-- Electric Power Functions Servo Motor 99498 18 -->

<Brick ldraw="99498.dat" lego="10130" />

<Transformation ldraw="99498.dat" tx="1.2" ty="0" tz="-3.6" ax="0" ay="1" az="0" angle="1.570796"/>

<!-- Electric Power Functions AAA Battery Box [72 Bottom] (Needs Work) 64228 18 -->

<Transformation ldraw="64228.dat" tx="-2.8" ty="-3.835" tz="1.2" ax="0" ay="0" az="0" angle="0"/>

Regards,

David

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Two additions;

<!-- Slope Brick 45 3 x 1 Inverted Double 2341.dat -->

<Brick ldraw="2341.dat" lego="18759" />

<!-- Slope Brick Curved 4 x 1 61678.dat -->

<Brick ldraw="61678.dat" lego="11153" />

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Update 2016-07-13

Added:

  • 18575 / 18575.dat (unoff) Technic Gear 20 Tooth Double Bevel Reinforced
  • 10089 / 99499.dat Electric Power Functions Large Motor
  • 10130 / 99498.dat Electric Power Functions Servo Motor
  • 64228 / 64228.dat Electric Power Functions AAA Battery Box [72 Bottom]
  • 18759 / 2341.dat Slope Brick 45 3 x 1 Inverted Double
  • 11153 / 61678.dat Slope Brick Curved 4 x 1

Thanks David (djm)!

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Update 2016-07-16

Includes some modifications from Mattia Zamboni’s (latest?) version (2015-09-30).

Added

  • 58181 / 58181.dat Slope Brick 33 3 x 6 without Inner Walls
  • 74967 / 30027a.dat Wheel Rim 8 x 8 Notched Hole, Reinforced Back
  • 90393 / 90370.dat Minifig Microphone
  • 30064 / 3957a.dat Antenna 4H with Rounded Top
  • 13731 / 13731.dat Slope Brick Curved 1 x 8 with Plate 1 x 2
  • 16577 / 16577.dat Arch 1 x 2 x 8 Raised
  • 30413 / 30413.dat Panel 1 x 4 x 1 with Rounded Corners, Thin Wall

Corrected

  • 30027 / 30027b.dat Wheel Centre Small Wide for Slick Tyre
  • 30028 / 30028.dat Tyre 14 x 8 Slick Smooth
  • 4624 / 4624.dat Wheel Centre Small
  • 3139 / 3139.dat Tyre 4 80 x 8 Single Smooth Type 1
  • 93609 / 93609.dat Arm Skeleton Bent with Clips Horizontal Grip
  • 92589 / 92589.dat Door 1 x 4 x 6 Lattice
  • 87414 / 87414.dat Tyre 6/ 50 x 8 Offset Tread with Center Band
  • 11299 / 11299.dat Ladder 2.6 x 16 with Handrails

(Re-)Rematched

  • 18579 / 18579.dat Slope Brick 45 3 x 1 Inverted Double

Edited by SylvainLS

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Update 2016-08-04

Added:

  • 23996 / 23996.dat Panel 8 x 8 x 6 Rock Corner

Corrected:

  • 11295 / 11295.dat Plane Bottom 6 x 8 x 1
  • 11301 / 11301.dat Slope Curved 2 x 8 x 2 Inverted Double
  • 30395 / 30395.dat Hook with Towball
  • 30396 / 30396.dat Hinge 1 x 2 Locking with Towball Socket
  • 43122 / 46667.dat Jet Engine Fan with 10 Blades and Technic Pin
  • 90202 / 90202.dat Technic Pin Connector Round with 4 Clips
  • 91347 / 91347.dat Crane Jaw Curved 2 x 7 x 2.5
  • 92402 / 92402.dat Tyre 14/ 50 x 17 with Centre Band
  • 92842 / 92842.dat Propeller 3 Blade 5.5 Diameter with Technic Peghole and Flat End Blades
  • 98282 / 98282.dat Car Mudguard 4 x 2.5 x 1

Rematched:

  • 18041 / 57467.dat Minifig Harpoon
  • 43903 / 43903c01.dat Belt 20 Tooth (Formed for 2 Wheel Rim 14 x 18)

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Update 2016-08-05

Corrected:

  • 92585 / 92585.dat Minifig Tool Crowbar
  • 92107 / 92107.dat Plate 6 x 8 Trap Door Frame with Flat Clips

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The right lines for the lego Batarang:

<!-- Boomerang Wing 55707c.dat-->

<Brick ldraw="55707c.dat" lego="98721" />

<Transformation ldraw="55707c.dat" tx="0" ty="0" tz="0" ax="1" ay="0" az="0" angle="1.570796"/>

instead of:

<!-- Minifig Utensil Batman Bat a Rang two wings with handgrip bar in middle 98721 35a -->

<Transformation ldraw="98721.dat" tx="0" ty="0" tz="0" ax="0" ay="1" az="0" angle="3.141593"/>

Corrected:

<!-- 97782 35a -->

<Transformation ldraw="97782.dat" tx="0" ty="-0.24" tz="0" ax="0" ay="1" az="0" angle="3.141593"/>

<!-- 95054 35a -->

<Transformation ldraw="95054.dat" tx="0" ty="-0.44" tz="0" ax="0" ay="1" az="0" angle="-1.570796"/>

<!-- Minifig Weapon Hand Dagger 88812 35a -->

<Transformation ldraw="88812.dat" tx="0" ty="0" tz="0" ax="0" ay="1" az="0" angle="1.570796"/>

<!-- Minifig, Weapon Bladed Claw 88811 35a -->

<Transformation ldraw="88811.dat" tx="0" ty="0" tz="0" ax="0" ay="1" az="0" angle="1.570796"/>

I also discovered that 2562 and 2561 are really broken, but I can't fix them with my current knowledge. If someone could take a look at that or teach me how to fix them I would be grateful.

Theodor

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Update 2016-08-07

Corrected:

  • 2561 / 2561.dat Minifigure Gun Musket
  • 2562 / 2562.dat Minifigure Gun Flintlock Pistol
  • 88811 / 88811.dat Minifigure Weapon Bladed Claw
  • 88812 / 88812.dat Minifigure Weapon Hand Dagger
  • 97782 / 97782.dat Figure Friends Cutlery Knife
  • 98721 / 55707c.dat Minifig Batarang

Thanks Theodor!

For 2561: I think it only needed a sign change but I started anew and recalculated everything, and ended up with a little different translation :grin:

(And I may not be consistent with what I say below for 2562 but I calculated the translation relatively to the barrel, not the stock, as the barrel is along an axis in LDraw (Y).)

For 2562: There is (again) a difference between LDD and LDraw. The transformation only needed a little vertical push to be correct if the handle is the reference (as I think it should be as, most often, it’s the way it will be attached to a minifig). It’s totally off if you want to attach it by the barrel. See attached picture.

flintlock.png

Edited by SylvainLS

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Thank you for fixing 2561!

The thing that would be interesting, maybe not only to me but also for other users that want to help out, is how you calculate the right translation for complicated pieces like the 2561? I think it would help out a lot with keeping this file up to date if someone could put a short tutorial together and post it here.

As for the 2562: it looks to me as if the LDraw model isn't acurate. Could that be?

With regards,

Theodor

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Thank you for fixing 2561!

Thank you for telling me about it first.

The thing that would be interesting, maybe not only to me but also for other users that want to help out, is how you calculate the right translation for complicated pieces like the 2561? I think it would help out a lot with keeping this file up to date if someone could put a short tutorial together and post it here.

Indeed, I began a howto but it’s not easy to come with the right level of details between boringly obvious and overly complicated.

As for 2561, the trick I used was placing the part in LDD so that its LDraw Y axis (up) would also end up in LDraw (vertical muzzle for 2561) and attaching clips at key points on the barrel. Once in LeoCAD, I could then translate the musket so that it fit in the clips. The Y translation (actually Z in LeoCAD) becomes ty (once converted from LDU to cm). The horizontal translation is somewhat difficult because which is X and which is Z depends on the rotations, but the absolute values are the good ones, so I just try tx then tz then adjust the sign :grin:

(Actually, for 2561, the horizontal translation was to be in Z because the horizontal axis of rotation was X. IOW, the part was pitched (LDD center), so its (LDraw) center moved in the YZ plane. But that’s also because both LDD and LDraw centers are on the YZ plane. So trying tx/-tx/tz/-tz is often quicker than figuring it out :grin: )

As for the 2562: it looks to me as if the LDraw model isn't acurate. Could that be?

Several parts differ between LDD and LDraw.

Look at 2561, the muzzle is slighty different, the stock is a bit longer in LDraw…

We also discussed 92692 the other day http://www.eurobrick...75#entry2623239

Also look at the minifig arms. Totally different.

I tend to think LDraw parts are wrong because parts are measured IRL for LDraw and that’s not easy to measure angles on round pieces (like MF arms) whereas I prefer to think that LEGO provided the correct geometry for LDD.

But, who knows? Maybe both LDD and LDraw are wrong. An audit would be needed :devil::tongue:

Edited by SylvainLS

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Well you sure got me excited for the how to now, (regarding the fact that I only understood half of what you tried to explain there) but until than, very quick question: are you doing the translation inside LeoCAD or how are you using it oder the for previewing the changes you made in the ldraw.xml file?

As for LDraw part accuracy: have you seen this website called http://www.mecabricks.com? All their parts were modeled by measuring the IRL parts.

I did here the same thing you did for comparison:

2561_comparison.png

Edited by TotiGonzales

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Well you sure got me excited for the how to now, (regarding the fact that I only understood half of what you tried to explain there)

See what I said about “overly complicated”? :wink::tongue:

but until than, very quick question: are you doing the translation inside LeoCAD or how are you using it oder the for previewing the changes you made in the ldraw.xml file?

I build a minimal model in LDD, export it, check the results with LeoCAD, edit ldraw.xml, re-export with LDD, re-check the results with LeoCAD, rince, repeat….

As for LDraw part accuracy: have you seen this website called http://www.mecabricks.com? All their parts were modeled by measuring the IRL parts.

I did here the same thing you did for comparison:

Yes, there even is a thread hereabout about it.

If you imported the LDD in Mecabricks and Mecabricks didn’t modify the position of the red clip to attach it to the flintlock (I don’t know if Mecabricks connects the bricks), then that means that, as LDD and Mecabricks models match, it’s the LDraw version that’s flawed.

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The "tx" value for 3711 is currently defined as 0.4. I believe it should be 0 (as below).

<!-- Technic Chain Link 3711 13 -->

<Transformation ldraw="3711.dat" tx="0" ty="0" tz="-.66" ax="0" ay="1" az="0" angle="4.712389"/>

David

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