Digital Modelling

Vickers Medium Mk.III c.1930
Back in the far distant past, I got pretty good at writing PovRay scene files in a text editor. Then a graphical front-end for PovRay appeared, called MoRay, and it was really good until it no longer worked with the new version of Windows (Vista), and the guy who originally wrote it lost interest in updating it. I believe he passed it on to the PovRay Foundation, but the last time I tried it, things hadn't really got any better.

Anyway, that was some years ago, and although I've dabbled from time to time I haven't really made the effort to come to grips with newer software.

As may have become apparent, I have an interest in the clunky rolling boilers that passed for AFVs in the inter-war period. Unfortunately, in my preferred gaming scales of 15mm (1:100) and 6mm (1:285 - 1:300), that period is very poorly served by manufacturers. However, now that 3d printing is beginning to mature, and reasonably high resolutions are now becoming available from companies like Shapeways, I thought I might see what I could do about the paucity of tanks from between the World Wars by building some digitally.

Machine-gun sub-turret
My software of choice is Blender, which is both very capable and free. I've tried it out before, when I was looking for a replacement for MoRay, but back then its UI was excruciatingly bad — it had clearly been designed by and for severely autistic engineering nerds, with little or no account taken of the needs or limitations of normal people, and with some truly unique assumptions about what was intuitive. Happily, it has been vastly improved since then. It's still not very straightforward to learn, but it's so much better that it might almost be a different program altogether.
Main turret

I decided to teach myself how to use Blender by building a Vickers Medium Mk.III, which (as far as I know) isn't manufactured by anybody anywhere in either 15mm or 6mm scales. So far, all I've got is the main turret and a front machine-gun turret, but it's a start.

I am learning a lot, but there's a lot more still to learn.


Turret with imported OBJ cupola in place
Here's a bit of progress for the morning.

I separated out the commander's cupola to its own file, and added some detailing to it. Then I exported it from Blender as an OBJ file, and imported it back into the turret file.

I don't know why the imported object is so much brighter than the native Blender stuff; I guess they use different default material settings. I haven't yet delved into any of that; it's not really relevant for the purposes of this particular model, which is 3d printing. However, I'll have to take account of it eventually.

I realised that I'd actually created the  main turret and mg turret at about 1:50 scale, not 1:100, so I had to do some resizing so that all the components would be consistent when I come to put them all together.

This will be about as far as I get today, I think. I've got the main shape of the hull complete, now it's just a case of adding all the bits.

Interestingly, the files size for the MG turret is much larger than for the main turret. I'm wondering if that's because I used UVSpheres instead of IcoSpheres for the rivets? I don't really know.

So far, modelling has been pretty straightforward — it's all primitives really, messed about with to one degree or another with Boolean sculpting. The side frames will be a bit trickier, I think; I might have to investigate some more advanced construction methods.

A little bit more fiddling about before I go to sleep. So many rivets.

February 3rd

Very slow progress today — most of my time was spent flailing about just trying to make that little grab-handle on the front of the driver's cupola. It turned out to be ridiculously simple once I found out how to do it, but the Boolean unions I was originally trying were driving me up the wall.

Apart from that, now the driver's cupola is also covered in rivets, and we have some track guards. It's progress, if slow.

February 4th

I've made a start on the rather complicated running gear, which has been an opportunity to try out importing and extruding SVG curves. It's not an entirely straightforward task, but it's really not terribly difficult either.

I created the form for the framework in CorelDraw, exported it to SVG and it went into Blender without a hitch. For some reason, Blender ignores the scale in the SVG file, and it appears in Blender's stage very, very tiny — it would be easy to assume that the import had failed unless you're prepared for that. You have to zoom right in to find it, and resize it a lot to get it up to its proper size. Also, the origin point for the curves is set way off to the side and needs to be reset. I have no idea why either of these things happen, but it does.

Since the finished model is intended for moulding and casting from a 3d printed master, it meant that I could simplify the framework a bit and make it solid, rather than the sandwich construction the original vehicle had.

Next up, wheels and tracks. That should be interesting. Once I've got this whole side finished, I should be able to just duplicate and mirror the whole thing to get the port side.

Running wheels and return rollers added. The drive sprocket and front idler will be ore candidates for an SVG extrusion I think. They could be built up within Blender, but it would be a chore.

Oh yes, and I'll be needing a track tensioning screw as well.

Well, putting the tracks on was a lot easier than I expected. The Array modifier saved a lot of time and fiddling around, though being able to set an offset value for simple duplications would have been almost as quick, and a bit more flexible as regards individual link rotation — it would have been easier to emulate track sag, for example.

The view from the front...

...and from the rear.

These things start getting a bit complex.

February 8th

I've gone back to the hull for the moment, to add all the clutter on the engine deck.

The exhaust pipes are going to be an interesting learning experience. I'm not really sure how to go about them, though I know that bendy pipes is something Blender can do.

Apart from the pipes, pretty much all that's left to do is the storage boxes that run along the track guards amidships. That and trying to work out what's wrong with my running gear file that makes it unimportable, and how to fix it.

As it turned out, the exhaust pipes were easier to build than I had expected, since I could just build them up from a filled, bevelled bezier curve transformed to a mesh.

On to the last leg. This has proven to be rather an enjoyable project.

The storage boxes have been added, and that is about that for the hull. No doubt there are more bits of detail that could go on, but essentially, it's done.

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