Optimize ArchiCAD 3D BIM Models to View on Mobile Devices

BIMx is GRAPHISOFT’s solution to explore, present, communicate and share design. BIMx enables architects and their clients to walk through professionally rendered 3D models with an easy-to-use navigation interface.

BIMx files can be exported from the ArchiCAD BIM software as a self-contained executable file for Mac or PC, or as a BIMx file that runs in the BIMx player app on iOS mobile devices such as the iPhone and iPad.

If you are not familiar with BIMx yet, you can try it now — just download a sample file along with the player environment from the Facebook-integrated BIMx community site.

How Large Can BIMx Models Be?

The maximum size of a model depends on the device where the project will be presented. BIMx uses OpenGL technology, so the video memory is often decisive. Still, due to smart optimization, even mobile devices can run amazingly complex models.

It is important to note that the BIMx file size is not indicative of the model complexity. What really counts is the memory usage of the geometry. When saving a BIMx file, this geometry size is calculated and labeled either Small, Medium, Large and Extra Large.

BIMx file save dialog indicates model complexity.

Small models run on any device. Medium size models will most likely run on mobile devices, but might be slower to navigate; while large models will only run on the latest mobile devices like iPad2 and iPhone4. Extra large models are not suitable for mobile devices, but will work well on desktops and laptops with powerful video cards.

How Can I Optimize Model Size?

By optimizing your model, you can achieve smoother navigation, especially on lower-spec devices. Optimization means lowering the size of memory needed to run your model. You can achieve this in three ways:

Lowering the polygon count of the model
Reducing the number and size of textures used
Exporting model without global illumination.

Lowering Polygon Count

With the help of ArchiCAD’s PolyCount Add-On (which is a goodie tool — see ArchiCAD downloads under ArchiCAD’s Help menu), you can keep track of the overall polygon count of your model.

You can reduce the number of polygons by:

Filtering elements — turn off layers of building elements that you don’t necessarily want to show in your model. Use the marquee tool to crop the model if you only want to show parts of it.
Reducing the complexity of objects — many library objects have settings for level of detail. Curved elements also have resolution settings. Lower resolution means fewer polygons.
Leaving out unnecessary details — plants, car and people objects are often very complex. Look for such objects with low polygon counts. Door knobs, faucets, taps are often very complex even though their model dimensions are small.

Optimizing Textures

The number and size of textures can greatly inflate the model size. Here are some tricks to optimize textures:

Use low-res, compressed images (e.g. .JPG files) as images. With an image editor you can reduce the texture map’s size to a size which still looks good enough in 3D, but results in a smaller .JPG file.
Use as few textures as possible. Make sure that similar materials use the same texture map file.
Don’t apply texture to elements whose model dimensions are small and therefore the texture doesn’t really improve the overall image quality.

Export Without Global Illumination

Global Illumination is an optional setting at model export that adds a more realistic lighting effect to the model, but uses considerable hardware resources. In the BIMx desktop viewer, you can check exactly how much video RAM it requires (see Figure 2). If a model proves to be too heavy with global illumination turned on, re-export the model a second time without this setting.

You can find more information about BIMx on graphisoft.com. If you want to learn more about optimizing your model for BIMx, check out our knowledgebase.

Author: Gergely (Greg) Kmethy, director of customer support at GRAPHISOFT