In preparation for my BIMx entry, I spent some time reading up on BIMx Optimization on the ArchiCADwiki. One of the suggestions is to download the PolyCount Add-On. You can download it here. When you’re building a file for export to BIMx, paying attention to polygons is important.

Here’s the polygon count of the original model.

Here’s the polygon count of the model once I deleted hidden geometry and created all the jagged burned out areas.

Two interesting things to note here. Delete everything you can’t see. For this model I deleted footings, some bathroom fixtures and trusses that were hidden in attic spaces. The BIMx optimization page recommends that you also turn off things like door knobs. Maybe for a 13 story apartment complex, but it’s unnecessary for a 6,000 sq. ft. home.

Now when I created the burned out areas of the house, I was expecting the polygon count to soar. I was nervous that my whole plan would fall apart because I couldn’t make my building look like a ruin. Turns out that I should have been worried about Objects…

The M1 Abrams Tank isn’t so big. I could add dozens!

I must really love that Airship. And it turns out all zombies are not created equal…

To create my BIMx zombie attack, I needed tanks, jet fighters, soldiers, and of course zombies. But at the moment there are not a lot of those available in native .gsm format. So I needed to explore Google SketchUp warehouse and sites with free 3D studio models. Expanding the search gave me lots of options. But there was a lot of garbage. Everyone seems to make SketchUp zombies. But only a few people make really good ones. And if you look at the polygon counts above, Zombie_3.gsm is 17,303 polygons while zombie_horde_6.gsm is only 7,908 polygons. Using the right zombies, I can double my infestation and keep my model size down! Who would have thought that a zombie could have twice as many polygons as a tank? The trick is to find a good looking model that is also low in polygons. Not so easy. And until you run the polygon counting add-on, you really can’t tell how big an object is going to be.

What’s with the blimp, Jared?

I really wanted to include a jet fighter in the model. Having one hovering in the air above the zombie attack reminded me of the end of 28 Days Later, one of my favorite zombie movies. Also suspending something in the air was a cool trick in a BIMx model, where otherwise gravity appears to work. Alas, all the jet fighter models I could find had two problems: HUGE polygon counts (smooth curved surfaces can be killers) and landing gear. Some of their polygon counts were well over 100,000. Way too big. But more problematic for me was the landing gear. People model jet fighters to sit on the ground, not appear in the sky overhead. Having an F/A-18 Hornet or A-10 Thunderbolt overhead with its landing gear down looked dumb. So no jet fighters flying overhead. But I found the airship. At 47,939 polygons it’s over 20% of the model and almost the size of the house (polygon speaking), but I think it just looks so awesome hovering over the zombie attack scene. So if you can’t view the BIMx file on an iPhone 3 or an iPod touch, blame the airship.

You can download the BIMx file here.