The Future Is Now – Part 2

In Part 1 I created the first draft of my texture stamp for customized Convergence bases.  First up was to export the model as an STL file (more on that later) for upload to Shapeways.  I used Shapweays mostly because they have an online 3D view of what the model looks like to them.  It’s a sanity check to make sure what you think you’re printing is what they’re going to actually produce.

 Step22 Step23

“Sloppy work as usual. Lisa’s casting spells at an eighth-grade level; you’ve sinned against nature.”

Obviously that’s not right.  It took a little trial and error, but here are the things I did wrong in creating the initial model.

 Blue Blocks

First up, I had some blocks that were blue while most were white.  The blue ones had the added problem of not having a bottom surface somehow.

Step20 Step21

I created a surface to cover the hole, but as it turns out the colour of the blocks mattered too.  After a little googling, I found that the blue signified an internal surface ie. one you weren’t supposed to see, like the inside of a block.  So, while to me the blocks looked fine, as far as the model was concerned they were a weird half inside out shape.  This is correctable by right clicking on each surface and selecting “reverse faces”, but since this is a recursive design, there were a lot blocks that needed correcting and each face needed to be reversed individually without missing any.

Too Edgy

Turns out that too many edges leave a sloppy model.  This can be a problem sometimes, so it’s best practice to remove any extra edges from the model to keep it clean.  Here’s a view from below my original model:

Step24

 

As you can see, that’s a lot of extra edges (about 1300).  Knowing what I know now, I would be able to delete these with clever area selection, but at the time my only option was to delete each of them manually, which was more tedious than I was willing to tolerate.

There are even hidden, internal edges that are left over from the copy/paste rotation.  These are edges that used to be part of an external face, but that face was lost when a rotated shape came into contact.  This still left an edge bounding nothing, which as I understand can be a problem too.

Step25

 

The red-marked edges used to be external, but became redundant when those surfaces became hidden.  Unfortunately they made their Tough roll and you need to make of point of removing them explicitly.

Format Wars

By default, SketchUp uses the .skp file format/extension which works fine until you need to get something printed.  It has a handful of other common formats you can export to, but not the (apparent) #1 format: *.stl (STereoLithography).  This can be downloaded as a plugin for SketchUp from the Windows | Extension Warehouse menu item; it’s called SketchUp STL and it’s by the SketchUp Team.  I have no idea why it wasn’t simply included from the get-go.

In any case, be aware that you need to export your model into a format the printer likes.  It’s probably best to use the printer’s preferred format to minimize and surprises.

Reconstruction

So, now that I discovered where I went wrong the last time, it was pretty simple (and quick) to avoid these pitfalls when re-making the object.  As I created each new shape, I used the Right-Click | Hide function to hide the surface to remove any internal, extraneous edges.

Step28

The red edges were removed

I also kept an eye out for blue surfaces.  I’m not exactly sure what causes SketchUp to determine what is the outside surface when I use the Push/Pull control.  However, if you use the Crtl key when you move the surface, you get a copy (just like Rotate from Part 1) and this seemed to help with keeping the blocks inside-right.  It’s also easier to maintain this if you can do it before you start duplicating things.

Finale

So, now that the object has been rebuilt, I exported it and sent it up to Shapeways for another sanity test.

Success!

Success!

Now that I have a correct model, I’m ready to source a printer!  Which I will discuss next time!

Author: CG

I am a software developer by trade with an interest in mathematics and wargaming. I love it when I can bring all my interests together at the same time.

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