Easy lithopanes with Simplify3D

[Toby]

Next stop---mapping onto a sphere (the "lithosphere"---get it?).

Hard to avoid distance distortion (i.e. mathematically impossible). But you could do fun stuff with it, like use google maps to do a litho-earth. That would be beyond cool.

IIRC, someone on this board - Dave?- was looking into doing this a while ago. Good things come in M2s!

[jsc]

I had the smooth side out because I thought it presented better that way. It is actually more work to do it that way as I have to do a two step molding process to get it on the inside. It would be easy to just take the embossed cylinder and cut a hole in it. I'll add that as an option. We're you able to do it in Rhino?

Tim, I'm wrapping around a full half cylinder, a quarter seemed too thin. You should have an option to take a panoramic 360 photo and do a full wrap!

[Tim]

I had a quarter cylinder only because I accidentally divided by two somewhere. . . !

And yes, Toby, the idea is to map an Earth projection onto the inside of a globe. The support structures will probably be a mess, but I'll get there when I get there.

[jimc]

jin, you know i didnt even bother trying in rhino. i know it has a very nice heightfield tool but its all built into s3d and you had the parameters right there so i did it that way. i have seen a video on it being done in rhino and they even put the image on a sphere like tim said. ill have to watch it again.

[jsc]

Oh, you're talking about the flat ones? In that case, I'm not sure what you mean by smooth side/textured side. You can just turn it over.

[jimc]

well yes you have the nice smooth side. the side flat against the bed which looks nicer being face out, like the smooth outer surface of the cyl you did. you get a nicer picture though when the light is shined through the smooth side and your looking at the printed/textured side. just more crisp and detailed. when on display though and light off that side doesnt look so nice.

[jsc]

My Thingiverse script has been modified to allow for the embossed surface on the outside of the cylinder, with two new photos showing how it looks. It does look sharper somehow on the outside.

[jimc]

right! its sharper because its not being diffused by the first 4 layers of solid white material.

[Tim]

I guess I'll have to revise my code now for an option to have an inside-out cylinder with the textured part on the outside.

I am close to having something to post/distribute. I have already made and sliced some models. However, I'm not going to upload this to Thingiverse until I have printed a piece, which I should do tomorrow. It's all in C code and it is very fast. I spent today cleaning it up and making sure that all the parameters can be entered on the command line, and all the values are in sensible units like millimeters. I still have not done the spherical projection but the flat plate and the cylindrical projection work well.

In the process I have discovered that S3D does NOT work well with large files. One of my images resulted in a 100MB (ASCII) STL file. It wasn't too bad until the slicer started working on it. . . then it blew up to over 8GB and nearly hosed my computer. What in the heck can its internal representation be that it runs into the gigabytes? It also has the problem that if you delete an object in S3D, the memory for that object is NOT freed up. So I would import a design to check how it looked, delete, fix the program, import again, and pretty soon I would have to shut down S3D and restart because it had maxed out my computer's memory. S3D definitely has memory issues. Eventually I wrote a routine in the lithophane program to reduce the image size so it would not be so big, and so with that and being careful to watch the computer's memory usage, I've managed to avoid maxing out the memory since then.

[Toby]

I
In the process I have discovered that S3D does NOT work well with large files. One of my images resulted in a 100MB (ASCII) STL file. It wasn't too bad until the slicer started working on it. . . then it blew up to over 8GB and nearly hosed my computer. What in the heck can its internal representation be that it runs into the gigabytes?

It could be plausible. If S3D keeps the geometry calculation for each slice, then with a lithophane type model, each slice might have a lot of vertices and small edges to store. But then I'm guessing it has to find all the vertices that are coincident with each other on each layer, since the STL file just lists each triangle separately and doesn't tell you which triangles share which vertices and edges. To write efficient g-code I imagine is it has to figure all that out for each layer.

Matching points can be done in linear (or near linear) time, but it may require lots of memory depending on the algorithm used. And at the same time, it has to do some layer-to-layer comparisons, which may also add to the memory burden if there's a tradeoff to be made between cpu time and memory useage.

There's no programming magic to it, but given that S3D is known for speed, it seems reasonable that memory usage is the compromise it makes. Plus of course is the likelihood of memory leaks in a program like this.