Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

LeoCAD – A CAD program for creating virtual Lego models

github.com

Post reply on HN
Print view View original

61–70 of 86 posts

Re: LeoCAD – A CAD program for creating virtual Lego models

#61

Post by pavel_lishin »

bonzini wrote: post #57
tgb wrote: post #55

Earlier quoted context omitted.

Honest question: why do they need a constraint engine? Can't everything be done in exact integer multiples of the smallest brick size?

You can build sideways whenever pieces have studs on the side, for example (the first brick with studs on the side was created in 1979 for headlights!). And also put sticks into hollow studs, "click" Technic pegs into holes, rotate Technic pegs and gears. And even place bricks and plates at an angle, using Pythagorean triples or careful rotations, and much more---this is what makes Lego fun for adults too! Despite re…

> And even place bricks and plates at an angle, using Pythagorean triples or careful rotations

Can you explain this a bit more? I'm having trouble visualizing what you mean.

Re: LeoCAD – A CAD program for creating virtual Lego models

#63

Post by bonzini »

pavel_lishin wrote: post #61
bonzini wrote: post #57

Earlier quoted context omitted.

You can build sideways whenever pieces have studs on the side, for example (the first brick with studs on the side was created in 1979 for headlights!). And also put sticks into hollow studs, "click" Technic pegs into holes, rotate Technic pegs and gears. And even place bricks and plates at an angle, using Pythagorean triples or careful rotations, and much more---this is what makes Lego fun for adults too! Despite re…

> And even place bricks and plates at an angle, using Pythagorean triples or careful rotations Can you explain this a bit more? I'm having trouble visualizing what you mean.

Pythagorean triples: for example, 3^2+4^2=5^2. For a length-6 plate the distance from the first to the last stud is 5, so you can place it at an angle of approximately 25 degrees, i.e. arctan 4/3, as long as there are no studs in the way (which you can achieve easily using tiles). On LDD you can place it horizontally, choose the rotate tool, and the constraint engine will automatically forbid invalid angles around arctan 4/3, where the plate would overlap with the stud, and "snap" to the right one.

An example of a rotation is to build two rectangles of the same size, and then place the topleft-bottomright diagonal of one rectangle on top of the topright-bottomleft diagonal of the other. The diagonals don't have an integral length, but the lengths are the same so it just works.

Re: LeoCAD – A CAD program for creating virtual Lego models

#64

Post by pavel_lishin »

bonzini wrote: post #63
pavel_lishin wrote: post #61

Earlier quoted context omitted.

> And even place bricks and plates at an angle, using Pythagorean triples or careful rotations Can you explain this a bit more? I'm having trouble visualizing what you mean.

Pythagorean triples: for example, 3^2+4^2=5^2. For a length-6 plate the distance from the first to the last stud is 5, so you can place it at an angle of approximately 25 degrees, i.e. arctan 4/3, as long as there are no studs in the way (which you can achieve easily using tiles). On LDD you can place it horizontally, choose the rotate tool, and the constraint engine will automatically forbid invalid angles around ar…

Ah, I thought you meant arranging them vertically, not diagonally across the horizontal directions. This makes a lot more sense.

Re: LeoCAD – A CAD program for creating virtual Lego models

#65

Post by yodon »

yodon wrote: post #53

I recall that one of the LeoCAD-style brick based editors had an option to remove all the top and bottom connection features for export to .OBJ or similar, simplifying the shapes to boxes but reducing the poly count enormously. Was that something LeoCAD could do or would I need to use a different tool for that? (This wasn't a general purpose hidden surface removal, it was just removing all of the parts of the bricks…

To answer my own question: the program was LdrDat2Obj[0] and it had an option to ignore stud.dat references inside brick definitions when exporting designs to .obj (you'll still be carrying all the weight of the unseen internal connection shapes but it still represents a pretty huge poly savings to exclude the top studs on export)

[0]http://www.pearse.co.uk/lego/links/ldrdat2dxf/

Re: LeoCAD – A CAD program for creating virtual Lego models

#67

Post by yodon »

Raphmedia wrote: post #62

What is the output? Could you build 3D models with "virtual legos" and 3D print them easily?

In principle, yes, in practice, no. The tolerances and surface quality achievable are far below what you require and expect when connecting or even just holding or looking at Legos. As ubiquitous as Legos are, they're among the highest tolerance, highest quality rigid plastic parts you're likely to encounter.

Re: LeoCAD – A CAD program for creating virtual Lego models

#68

Post by Raphmedia »

yodon wrote: post #67
Raphmedia wrote: post #62

What is the output? Could you build 3D models with "virtual legos" and 3D print them easily?

In principle, yes, in practice, no. The tolerances and surface quality achievable are far below what you require and expect when connecting or even just holding or looking at Legos. As ubiquitous as Legos are, they're among the highest tolerance, highest quality rigid plastic parts you're likely to encounter.

What about printing an entire model and not the pieces?

In other words, could I "build" models with that software without any knowledge of 3D modeling and use those models to 3D print?

Re: LeoCAD – A CAD program for creating virtual Lego models

#69

Post by pbhjpbhj »

edraferi wrote: post #48
mschaef wrote: post #46

Earlier quoted context omitted.

Sounds difficult to achieve. I attended University of Texas at Austin, and the campus has a central tower that my psychology professor used as an example of something phallic. The dividing line would have to be rather precise not to exclude too much.

If I remember the original article correctly, it WAS too hard. It proved impossible to prevent offensive shapes from sneaking in. It actually killed the game. When Minecraft came along a few years later, they avoided the problem by making users host the servers. This shifted liability away from the central developer and put the onus on the player community to sort themselves out.

>This shifted liability //

If I user makes a suggestive shape out of lego blocks inside a 3D game, what liability is there? Much less surely than any of the text chat you get on virtually any online game??

Does/had Minecraft ever had a major problem with what one might term "phallo-philes"?

Re: LeoCAD – A CAD program for creating virtual Lego models

#70

Post by pbhjpbhj »

jve wrote: post #23
kuschku wrote: post #19

Earlier quoted context omitted.

LEGO’s patents expired a while ago, and competitors such as KREO have replicated the shapes and some of the models already. That said, no one is going to print LEGO – actual LEGO is a lot more robust and stable than anything you could print yourself.

Oh, I see. But replicating the existing plastic cube was not what I actually thought. I thought: what if I print/manufacture lego mega blocks from whatever material.

You can't make "Lego bricks" as Lego is the trademark giving the origin of specific bricks but you can make near identical (missing the wording "Lego") bricks if you wish. If you do it at home and completely without any commercial aspect [giving them away can be commercial, so you have to take great pains to avoid being commercial] then you can make identical ones AFAICT.

This isn't legal advice of course.

Post reply on HN