I've had a couple of requests from people wanting to know how I built the Grandeur's
impulse engines, so I've decided to do something I very rarely do and post a tutorial. There's really nothing fancy about it and it's probably not going to rock anyone's world in terms of technique, but some of you might find it useful.
I'm going to build this up in layers, starting with the illuminated back plane, the part that actually glows.
Next, I created a set of grills through a combination of spline extrusion and poly editing. Note the two columns of wider segments in each grill piece; when viewed from a moderate distance, these create a variation of that subtle banded effect that was first introduced on the Enterprise
Then we have the actual engine housing, created through standard subdivision modeling techniques.
And for some added detail, I broke out the inner surface polys, edited them into short, even segments and then extruded them slightly.
It should be noted that the actual modeling work for all of this was mostly done in reverse, starting with the engine housing and extruded details, then the grill, then the back plane.
The final step was the addition of a standard spotlight, its beam spread asymmetrically scaled to fit the rough proportions of the engine aperture. This spotlight was set to include only the back plane for illumination and does not cast shadows. The hotspot and falloff were adjusted to make the glow a little brighter in the center.
Using the Mental Ray renderer, the back plane catches the light from the spotllight and glows appropriately, reflecting some of it back onto the grill and the engine housing in a realistic fashion. If you use the scanline renderer, the back plane will glow but you won't get any reflected light.
Here's the end result:
In my example, I'm using a darkish gray hull texture on the back plane because it makes the glow a little less even, but you really can't see it at normal viewing distances so it's probably better to just use a flat color tone. You'll have to experiment with the back plane color and the spotlight color to get the exact hue of impulse glow that you want. You can, of course, vary the glow intensity by simply changing the intensity of the spotlight.
You can also apply texture map "filters" to the spotlight if you want to match the shape of your engine aperture more precisely or don't want to mess with asymmetric scaling of the spotlight. Map filters can also let you do other things like invert the brightness levels so the engine aperture glows more brightly around the edges rather than in the center, which is something I'm thinking of trying myself.
If you want to get fancier, you could probably bake some self-illuminated textures into the engine assembly and eliminate the spotlight altogether. Calculating the reflected light among all those grill and engine housing surfaces does slow down render time a bit, even with minimal bounces and no shadows being cast. In fact, the impulse engines and the warp grills (which are lit with identical techniques) are the slowest rendering parts of this entire model by far.
Anyway, I hope that answers the questions of those of you who have asked how they were done.