BIMx: Notes on Model Data, Size, Textures and Shadows

These tips are intended for optimizing the ARCHICAD model before saving it in BIMx.

The ARCHICAD Model Unit preference (e.g. Imperial or Metric) will be used by default when the BIMx model is opened in a viewer application.

If your BIMx model is going to be viewed on hand-held devices such as the iPhone, further optimization of the model may be desirable to improve performance.

For more information, consult the BIMx page from GRAPHISOFT’s website at
http://archicadwiki.com/BIMx/Optimization.

Use Element ID Fields (For BIMx Hyper-models in Teamwork)

Each ARCHICAD element has an ARCHICAD ID, defined by default in its Tool Settings dialog box, under the Classification and Properties Panel. Make sure that your ARCHICAD model elements include this Element ID data for best results in BIMx (if you are in a Teamwork environment).

Background: In a Teamwork context, BIMx provides smart feedback on multi-selection, identifying each element by its ID. If the ARCHICAD model does not include this element ID data, BIMx cannot provide ID-based feedback on the selected elements.

Limit “Extra” Model Content

If you run into memory limits while creating the BIMx model (for example, during Global Illumination initialization), try eliminating or reducing the following model components. This will help optimize model size and improve BIMx performance:

furniture (e.g. chairs)

GDL objects (e.g. door handles)

other objects originating from Add-Ons (e.g. trees, cars, people)

other non-essential elements

Typically, such “extra” elements devour a great deal of memory. A single chair can require more memory than all the walls in the project.

Texture Formats

BIMx supports the following surface texture formats: jpg, bmp, tif, tga, png, gif.

If a texture would fail to load for any reason, the object that uses it will be drawn with the material color instead.

Alpha Channel Texture Effects

BIMx supports alpha channel texture effects with 32-bit tif, tga and bmp images. For the alpha channel effects to be detected inside BIMx, you must enable transparency in the ARCHICAD material/texture properties.

However, transparent objects are not necessary visualized using the correct display order – to do so would put a big dent in your performance.

Shadows

Shadows in BIMx are rendered using the OpenGL ARB_shadow extension. It works by rendering the scene, from the sun’s point of view, into a texture map. This texture map is then projected onto the scene and OpenGL will determine whether a pixel is in shadow or not. Larger texture maps will produce higher quality shadows. The maximum size is determined by your graphics card (the graphics memory available and the maximum texture size allowed). Some graphics cards may have 256 MB on-board memory, but only allow a maximum texture size of 4096 x 4096. A shadow texture is typically 24-bit.

8192×8192 shadow texture will consume 200 MB of video memory.

4096×4096 shadow texture will consume 50 MB of video memory.

2048×2048 shadow texture will consume 12.5 MB of video memory.

BIMx will automatically try to generate the largest possible shadow texture, starting with 8192×8192. Next, if this fails, it will try half that size, and so on.

To turn off the sun shadows, set sun shadow brightness to a value near zero.

Sun Shadow Artifacts

Depending on the amount of available video card memory and the (physical) size of your model, the sun shadows may display artifacts. This is due to the fact that BIMx cannot fit the whole model into the shadow map with good quality. Smaller models and more video graphics memory will improve the result. Global Illumination produces better shadows, which however are static.

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