View Single Post
Old May 2 2009, 04:34 PM   #60
Cary L. Brown
Rear Admiral
Location: Austin, Texas
Re: Another take on the Original Enterprise...

Psion wrote: View Post
Is every window double-glazed like the ones in the lounge?
Well, they're not "double-glazed" at all... but I can see why you'd be thinking in those terms.

CAD packages like Pro/ENGINEER are different than "rendering packages" like Lightwave or Maya or 3DS or Blender or whatever. Those are surface-based... they model surfaces without "really" modeling the material between surfaces.

CAD packages model solids, however. So a single pane of glass... one solid... has two surfaces, a front and a back.

That's what you're looking at here - a thick plate of glass (or glass-like material... and NOT "transparent aluminum"... AAAAGGGHHH!)

Here's a section from within Pro/E showing the vertical row of windows in the dorsal.

And a bit more detail.

Note that the hull thickness is a parameter I set up for the model, and this is uniform throughout the ship. Though I'm not required to use a parameter to assign a value to any feature (basically, when I create a feature, I either type in a value, or assign a variable to that value), I've done so uniformly through this ship so far for hull thickness, with the sole exception being the nacelle pylons.

When creating windows (not the round sensor portholes, which I'm doing differently), what I do is create a sketch (or multiple sketches in some cases) representing the window in a 2D state.

For instance, for the dorsal, I sketched them on the "side" datum plane (the one which, if sectioned through, gives the "side-view cross section" I've shown you a few times). For the primary-hull edge windows, I'll do the radial - that is, vertical - lines from the underside view, and the elevation from the side view.

Several people have asked me about how I'm doing this, so I thought I'd give a step-by-step example of how this is done. Realize everything you've seen so far has been geometry... no texture-work whatsoever. Obviously, for rendering work, it's still desireable to have as much of this done as texture, rather than geometry, as possible... but that's not the approach I'm taking here. I'm trying to model the "real" ship," not for rendering purposes but for engineering purposes. If what I come up with eventually becomes used for rendering purposes, I'd hope that the people doing that (probably not me... there are other people who are far better at that than I am!) would "optimize" things for rendering, and probably much of what I'm doing as geometry would be texture-based. My approach is far more precise, but but far too inefficient for rendering use.

First, I've got a fair number of what Pro/E calls "Style" features... including a subset called "trace sketches" which allow me to import bitmaps onto datum planes, scale and rotate and so forth, and use them as references. This technique is central to what I've been doing here. In this case, I have the underside view (reversed, obviously) on my "top" datum plane. I'll do my sketch on the top datum plane as well. (Note that virtually everything starts out as some form of 2D element, and is transformed into 3D. While it's possible to do "freeform 3D surfaces" in CAD, it's not really the main function, and that's not used terribly often.)

From there, I create a dimensioned sketch. I create real, mathematically-precise details which are intended to represent, as closely as possible, what I see in my "trace sketch" feature. Note that there is no real connection between the trace sketch and the dimensioned sketch here, other than I'm "eyeballing" my "real" sketch to be as close to the "trace sketch" as possible.

That (2D) sketch looks like this when completed.

I then "project" that sketch onto the appropriate 3D surface(s)... in this case, several surfaces on the exterior of the primary hull underside. Once this is done, I can hide (not "delete"... in CAD you can't remove parenting like you do in rendering packages) the 2D sketch.

Okay, so I've got a series of 3D curves on a 3D surface, but that's not really useful yet... it doesn't represent solid geometry, which is the language this software really speaks. So, how to convert it into that?

Here's the step-by-step:

1) Select the appropriate geometry - in this case, a surface. (It's possible to do this with multiple surfaces at once, but I did that on the "Vega" and it caused me some problems, so I try to avoid that now if possible.)

2) "Copy" and "Paste" that surface... this creates what is called a "quilt"... a simple surface feature (again, not useful unto itself, but used to create other forms of geometry). Note that, initially, the new "quilt" consists of the entire region originally chosen.

However, it's possible to only copy the portion of the surface within a boundary. This boundary can be determined through any geometry (edges, datum curves, etc), but in this case I'm doing it with my sketched-and-projected datum curves.

3) Note that I did the outside... and I want that to be a "raised edge region" surrounding the triangular detail. This means I need to "trim" the inside region out, to only have that outer strip.

4) At this point, I've got a new "quilt" which is coincident with the solid surface but only consists of the region bounded by the inside and outside "loops" of that shape. I then "thicken" (one of a number of potential solidification techniques available to me in this package) that. I'm choosing to thicken that by 0.060m for most "outline" surface details like this. Note that a surface really needs to be offset to have a different appearance... but also that in a "real" ship, these markings probably aren't "markings" but rather "frames" around hatches or panels or whatever, so they really should be offset anyway.

5) Okay, so now I've got a raised outline. I also want the interior region to be separate from the "normal" hull surface, so I'll copy and offset that as well. Note that when I select the surface, it is now in two regions... this is because the new feature I just created subdivides the surface.

6) I copy this surface then paste it, but I now need to use a different option... which I think is self-explanatory from the below:

7) So now I've got that inner surface copied as a new quilt. I can thicken that, now. Note that I can adjust the "thickening" by direction, I can add or subtract material, etc. To illustrate how this really works, I'll exaggerate the thickening here. Since this "triangle" is my "transporter emitter antenna," I want it to be an applied exterior antenna, so I'm offsetting it by 0.030m. But this shows how the tool really works.

Now, once that's done, I've got solid geometry which matches the information from my "trace sketch." In cases where there are multiple views, and those views don't actually match up (often the case when drawings are done in 2D tools, but never the case if the drawing is done using a 3D tool for what I hope are obvious reasons!) you sometimes have to make "compromise" decisions. In this case, I've shown you the "Sinclair drawing" (which is my primary reference in this project) but I also have been comparing the Casimiro and a few other sets of plans as well, in much the same fashion.

8) However, it's not really visible... it's "too subtle" in this case to even be recognizable. So, I set the color of the surfaces to something different... something "eyeballed" to look like the real models' coloration. I'm not trying to be very precise, here, in that regard... remember, I'm concerned more with geometry than I am with appearance for this project. So I've got a fairly limited pallet of colors I'm using. I can create more, but since (once the design is completed) I'd be creating new "materials" within whatever rendering package I eventually export it to, I don't see much reason to spend a lot of time stressing out over matching colors exactly.

Once all the details are done, the "projected sketch" needs to be hidden, of course.

Anyway... here's the final result.

Obviously, this isn't the ONLY technique I've been using, but it's what I'm using for most of the "surface details" (like my windows). In the case of rectangular windows, I'm creating the surface "quilts" at the window locations, creating offset copies (at 1/3 and 1/2 of the hull thickness) and then thickening them in opposing directions (removing material rather than adding it).
Cary L. Brown is offline