nGene

by Gene Turnbow | Jan 22, 2003 | Code, Lightwave

The nGENE
Here’s the source code and compiled binaries for my little OpenGL engine, which I have named the “nGene” after a suggestion by a coworker.

It’s a little odd as engines go in that it loads Lightwave 6.x (or greater) scene and model files and renders them, and then lets you fly a camera around and look at them. It lights the scene according to whatever lights you put in the scene, but all lights are translated as point lights. I never got spotlights or area lights working. It does respect global ambience settings in the scene, though, as well as maintain the hierarchical relationship between all the scene elements (i.e., parenting of scene elements is preserved at runtime.

To clarify the copyright status of the nGene, it’s open source and licensed under the LGPL, meaning you can use this code for your commercial projects if you wish, without having to worry about having to release the code for it or your own project along with the compiled form. By all means, steal the parts you like and toss them into your project if you think it’ll help. It’s why I wrote it in the first place. Note that I’m not responsible for the results, i.e, if it breaks, you get to keep all the pieces.
If you do download it, note that you’ll be in good company – the nGene has been downloaded over a quarter million times since I originally posted it.

Special thanks to gifted artist and animator Eric Estrada, currently a lighter at Dreamworks, for the 3D scan of his head.

It texture maps, but only UV textures, and there are a few ways to apply the textures in Lightwave that don’t actually work. The best approach seems to be to convert whatever conventional texture mapping you might have on your models into UV maps using the “Make UVs” tool in the “Map” toolset in modeler. Since the loader doesn’t handle DMAP chunks, models using cylindrical or spherical mapping need to have the vertices split at the seam, or you’ll get mapping errors. Also, I never got around to writing the polygon smoothing algorithm, so for now it’s flat shaded only.
The source code will compile under either Windows, using Microsoft Visual C++ 6.x or greater, or under Linux using GCC. Yup, it’s cross-platform code!
Download the source code, binaries and sample data here. It’s about 3 megs because of all the model files and textures and whatnot that you get with it. I wouldn’t get too excited if I were you – once I got the object and scene loaders working, the rest of the engine was done in about five days. It does give some good example code for reading objects in native Lightwave LWO2 format, though. By the way, in the ‘credit where credit is due’ department, I started with the example ‘C’ loader code written by Yoshiaki Tazaki at D-Storm.

UPDATE: I’ve only just now gotten around to fixing a problem with the project files that kept you from using KDevelop 2.1. I know 3.0 is out, that’s next, but at least this version works in Linux now. It’s a tarred, gzipped archive.
Once you’ve gotten it to compile (it shouldn’t be difficult if you know how to use the compiler at all), run it by giving a parameter of either a model file or a scene file. If you give it a scene file as a parameter, it’ll assume all the assets are right there in the same directory with you, even if the scene file says otherwise. If you give it a model file as a parameter, it’ll just load the model file and let you spin it around and look at it from different angles. If you can’t compile the project or don’t want to bother, binary executables are included for both Linux and Windows.
Interestingly, the Linux version runs significantly faster than the Windows version does, even though it’s exactly the same code. I think Linux just works better from the standpoint of interfacing the OpenGL API with the hardware. I know I could do a lot more about optimizing the rendering pipeline, though. Right now the only thing I do is sort the polygons by material; this cuts down on having to use the GL material commands for every single darned polygon, and it sped things up a lot. It’s still not a really quick engine as engines go, but it’s quicker than it first was.
I wrote this engine as an exercise, and I stopped before I finished it. There are leftovers and leavings of various ideas in it that I never implemented. The object and scene loading classes themselves are fairly clean, however, and I did my best to keep that functionality as encapsulated as possible so they could be reused by somebody else if needed. So don’t cringe when you read the code. You’ve been warned.

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It was used by the UCLA Laboratory of Neuro-Imaging – here is the testimonial letter I received from Craig Schwartz:

E-MAIL: craig@nospamplease.loni.ucla.edu

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Dear Gene, a few weeks ago you helped me with nGene – which I’ve been using to debug a small java library which creates LWO files as output. Although the contributed ModelViewer module did not have everything I wanted, and was unable to display the largest of my test data sets, it did enough (supported by nGene) that I was able to use it to keep my coding, thereby contributing significantly to my successful project.
Many thanks!
Craig SchwartzUCLA Laboratory of Neuro-Imaging