How to optimize BIMx Hyper-models

[Marton Kiss]

Large, complex BIMx models can be difficult to open on mobile devices as these platforms don’t always have the sufficient hardware resources to handle the same files that work fine on desktop or laptop machines. This is one of the reasons we've developed a new solution for BIMx, which is currently available on iOS and the recently released BIMx version on Android. Older versions might have some issues opening large models.

There are a few tricks available to tailor the BIMx model in a way that it opens smoothly both on iOS and Android older and new BIMx versions: this article helps optimizing the Archicad model before saving it in BIMx format.

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Mobile Device Requirements

As a first step make sure that your device has the sufficient hardware to open BIMx files. The bottleneck at model opening is the available RAM. This is not the available storage space on the device but the memory that the applications use when they run. The GPU in the device is needed for the 3D model display.

• Check the detailed system requirements for mobile platforms here
• Supported devices:
  • iPhone 7 and newer
  • iPad 6 and newer
  • iPad Mini 4 and newer
  • Android based devices running Android 4.4 or higher with Tegra3, Mali602, PowerVR SGX 543, Adreno 302 or faster GPU, minimum 1GB RAM (2GB recommended) and minimum 1,2 Ghz dual core.
  • Please note that the new Android BIMx application is running on Android 10 and 11.

•  Recommended Devices
  • iPad Air 2
  • iPad Pro
  • iPhone 12
  • Samsung Galaxy Tab S7 or newer
  • Samsung Galaxy S20 or newer

• File size limitations on Android devices

3D Model Size	~ 35 MB	~ 70 MB	~ 400 MB
Geometry Size *	< 100 MB	< 250 MB	< 500 MB
RAM required	512 MB	1 GB	2-3 GB

 NOTE

The BIMx model size that your mobile device can handle efficiently depends on many factors, including system memory, graphic card memory and the settings used for the active 3D window (global illumination, outlines, map etc.); thus, the information in the chart is only a guideline.

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Optimizing BIMx files for use on a Mobile Device

Optimize the Archicad Model for BIMx:

• 1) Optimizing Model Size
  2) Optimization of Textures
  3) Shut Down Background Applications on your Mobile Device
  4) Optimizing Model Quality

This document contains recommendations for optimizing your Archicad model if you plan to save it to BIMx format, especially if you plan to view it on mobile devices with previous BIMx applications.

Why should you optimize your Archicad models?

Model optimization in Archicad improves your 3D performance and navigation experience, even if you do not export the model to BIMx. However, the following problems may arise in BIMx in particular, due to limitations of the device used to view the BIMx file:

• slow navigation speed and low frame rate in 3D
• application freeze due to lack of memory
• slow upload/download speed due to excessive file size

Optimizing the model in Archicad can achieve the following results:

• increasing navigation speed
• allowing your projects to run on devices with limited memory
• improving the navigation experience of your clients

Consider Limitations of Mobile Platforms 

Before displaying your Archicad model in BIMx on mobile devices, you must take into consideration the memory and performance limitations of your mobile device.

The main limiting factors to consider:

• CPU
• Memory
• Video card

BIMx models intended for mobile devices must be further optimized compared to their desktop version.

If your model exceeds the limits of your device, you may encounter the following problems:

• Projects which run smoothly on desktop computers may be slow on mobile platforms.
• Some large models can't be loaded due to the lack of memory.
• Certain display options for the model will automatically be eliminated in BIMx.

Optimization Essentials

You must consider two aspects of the Archicadmodel - size and quality - and take steps to optimize them.

• Reduce the size of Archicad model. Do this by reducing the number of 3D polygons and the number and size of textures. See: Optimizing Model Size.
• Improve model quality. Do this by correcting modeling errors and taking other steps to improve navigation. See: Optimizing Model Quality.

Optimizing Model Size

Too many 3D polygons in the BIMx model can significantly slow down the 3D navigation. Excessive polygon count may even prevent BIMx from loading the project.

Please note that a large polygon count and large file size do not necessarily mean a big building. In many projects, a significant proportion of the 3D polygons are generated from library parts. A detailed furniture object can easily contain more polygons than the structural model of the entire building.

Thus it is essential to keep the 3D polygon count within an acceptable range. The following section contains useful tips for how you can check and control the number of polygons within your Archicad project.

Model size checking in Archicad: The PolyCount add-on

PolyCount is an Archicad “goody” add-on that helps to analyze and control the number of 3D polygons in Archicad models. The advantage of using this tool is that you can control the size of your Archicad model before you export it to BIMx.

PolyCount displays the number of 3D polygons grouped by element types (walls, slabs, doors, windows, objects etc.) and their percentage compared to the complete model size.

The add-on also allows you to change the 3D detail level of certain library parts in your projects. Most objects in older Archicad library include a “3D Detail Level” parameter with options for “Detailed”, “Simple” and “Off” representations. In newer Archicad versions "by MVO", "Full", "Simplified", "Schematic" and "Off" parameters are available. In the PolyCount dialog box, the “Default Level of Detail” function allows you to toggle between these values for all 3D objects in the projects.

Download PolyCount Add-On

The PolyCount add-on can be downloaded by clicking on the “Archicad Downloads” link in the Archicad Help menu. After successful installation, PolyCount can be activated from Window > Palettes > PolyCount. Please refer to the PolyCount ReadMe file for more information on using this Add-On.

Optimizing Large Hyper-Model Files for BIMx 

If the size of the Hyper-model exceeds the capacity of the device, then the BIMx app will quit while loading the file. Try the following to optimize the Hyper-model:

• Split the model into multiple 3D views in Archicad (e.g. left/right wing of the building), then publish these views to a hyper-model file. This way, you make full use of the available memory, and you can navigate among the part views easily within the app.
• Skip global illumination calculation, because GI data might be a significant part of the file size.
• Reduce the number of model polygons by hiding the less significant model elements.

How to Reduce 3D Model Size

The following tips can help you to keep the Archicad model size in an acceptable range:

Make Layer Combinations

Layer Combinations allow you to show only those elements of the Virtual Building model that are actually needed in the active 3D window. For example, you can create a layer combination dedicated to external views, such as renderings or elevations, in which you turn off all the elements located in the building's interior, so they can't be seen. Other layer combos can be defined for internal renderings or sections, in which the external trees, vehicles or other environmental elements are hidden.

Use the Marquee

To show only a part of the building (e.g. a room or a story), select it with a marquee. This simple trick can significantly decrease the model size and speed up navigation in BIMx.

Hide unwanted Objects in 3D

Each library part (except for 2D symbols) that you place on the floor plan has a representation in 3D views, even if you only intend to show them on the floor plan. Moreover, many of these elements generate a large number of polygons in 3D. To avoid generating these polygons, turn off the 3D representation of these objects with the corresponding parameter on the object's parameter list.

Since all library parts in the Archicad library have the same parameter name for this function, you can select multiple objects on the floor plan and collectively turn off their 3D. You can also put these objects on a hidden layer in the 3D View.

Control the Objects' Level of Detail

Library parts in the older Archicad library have a parameter for 3D detail level (simple, detailed, off) and curve resolution. Set these parameters to the minimum that is appropriate for the required 3D view. Too many segments in a curved shape can greatly increase the number of 3D polygons in a model. In some cases you can get better representation of the object with fewer polygons if you keep the 3D Detail level on "detailed" but reduce the curve resolution.

In recent Archicad versions most of the Archicad Library Objects have "by MVO", "Full", "Simplified", "Schematic" and "Off" parameters. The resolution can result higher number of 3D polygons as in older Archicad versions, thus we recommend to minimise this value for the optimal BIMx 3D model size.

Avoid Using Memory-Intensive Library Part Options

Some optional features of Archicad objects can generate a significant number of 3D polygons without producing noticeable differences in the final BIMx models. Use the following parameters with care:

• Handles for doors and windows

• Taps for bath tubs and lavatories

• Curved railings on stairs (including StairMaker stairs)

• Too many leaves on plant objects

The following table shows the polygon count of some Archicad library parts. Note that a single "Man Hands in Pockets" object generates as many polygons as 1066 walls! A further example that underlines the importance of polygon reduction is an office chair (Office Chair 01), which by default has 1389 polygons in 3D view - the equivalent of 232 walls. Such an office chair may be placed many times over in an office project, yet can be optimized out for purposes of BIMx navigation.

Element Type	3D Polygon Count
Wall without opening	6
Wall with empty openings	10
Door 25	88
Door 25 with knob (Style 1)	452
Basin 25 (Simplified)	263
Basin 25 (Full)	1124
Basin 25 with tap (Simplified)	284
Basin 25 with tap (Full)	1205
Man Hands in Pockets 25 (Full)	6396
People Bitmap	1
Office Chair 01 25 (Simplified)	1389
Office Chair 01 25 (Full, Resolution = 8 )	3236
Office Chair 01 25 (Full, Resolution = 16)	4740
Car 01 25	5208
Vehicle Bitmap	1
Straight StairMaker stair/“Post with Baluster” railing	789
Straight StairMaker stair/“Simple Surface” railing	789

Pay Attention to Complex Modeling Elements

Advanced modeling tools such as Curtain Walls and Complex Profiles or solid operations may also produce large numbers of 3D polygons. When optimizing a model destined for BIMx, consider omitting or limiting these situations that typically produce many 3D polygons:

• Detailed or curved Curtain Wall frame profiles

• Detailed Curtain Wall Accessories (e.g. shaders)

• Complex profiles with many line segments

• Solid operations between curved elements

• Many solid operations between model elements

In this picture the detailed Curtain Walls make up nearly 87% of the 3D polygons, increasing the overall number of polygons over 3 million.

Regularly Check the Model with PolyCount

Data in the PolyCount dialog may help you to identify other high-polygon-count elements (in addition to regular library parts) in the model such as:

• Complex Mesh models (e.g. site model)

• Elements imported from external applications (e.g. 3D Studio, SketchUP, 3D DWG, Cinema 4D, etc.), which are usually very detailed models, intended for use in high-end renderings rather than architectural visualizations.

Filter the Content of the 3D Window

In addition to the Marquee Tool and Layer combinations, you can filter the 3D view using View > 3D View Options > Filter elements in 3D to define which stories should be displayed in 3D.

You can even filter which Element Types you want to show in 3D.

Use Texture Mapping

Use texture mapping and alpha-channel transparent pictures instead of physical models. This solution can be extremely useful if you do need a large number of trees, vehicles, fences and other complex objects in the model.

Optimization of Textures

Carefully selected and correctly applied textures will enhance the quality of your BIMx models and improve the navigation experience in 3D. However, you should pay special attention to the number and size of the texture images. Oversized image files can significantly increase the BIMx project's memory usage and slow down navigation without noticeably improving the quality of your model. The following guidelines will help you to keep the size of your texture library in the optimum range:

• Use the same texture images for similar finishes
• There is no need to apply textures to elements which are not noticeable because of their size or position in the model
• The size and quality of texture images should be reduced to the minimum. You can compare the result of using different image sizes in the Archicad 3D window.
• Prefer compressed image file formats (e.g. JPG) to uncompressed ones (e.g. BMP)
• Use photo-editing applications to reduce the size and increase the compression level of your texture images
  
  Please note that Archicad can display maximum 4096x4096 pixel size Textures in OpenGL. The same limitation is valid for BIMx web and desktop apps. Similar resolution is displayed in Android BIMx Legacy. On iOS and Android BIMx, Android BIMx Lab: the new 3D Engine of these apps can display textures in a maximum of 1024x1024 pixel size. We are planning to increase this limit in the future.

Shut Down Background Applications on your Mobile Device

In some cases, when you want to open large BIMx models, you might have to close all these applications to allocate the maximum amount of memory to BIMx.

Optimizing Model Quality

The accuracy and precision of the Archicad model greatly affect the viewer's experience when navigating in BIMx. The following recommendations will help you to provide the best possible BIMx model for your customers:

Before you export the model to BIMx:

Carefully check its exterior and interior in the Archicad 3D window (with the OpenGL engine). Check for the following modeling mistakes:

• Missing or incorrectly applied textures
• Too dark or too light textures and materials
• Overlapping surfaces (the surfaces of different elements in the same plane). These will cause a flickering effect during navigation.
• Rooms that are not accessible (missing doors, other elements blocking the entrance)
• Unnecessary elements in the model, such as elements hidden by other elements (ducts behind the ceiling)
• Incorrectly joined elements (walls, beams, slabs etc.)

When exporting the model to BIMx: Before you initialize the Global Illumination calculation, look at the model again:

• Turn on the gravity and navigate across the building, checking for the mistakes listed above.
• Return to Archicad and correct the problems if necessary.

After taking these steps, publish the BIMx Hyper-model and open it with the BIMx App. If the project doesn't fit into the memory of the mobile device, return to the Archicad model and reduce its size as required.