Table of Contents

Use EasyAR Mega in Unity to implement occlusion

Occlusion is a key technology for improving the immersive integration of virtual and real content in AR. This article describes how to implement occlusion effects in Unity through EasyAR Mega.

Before you start

How occlusion is implemented

  • Offline modeling: in the Block coordinate system, create 1:1 matching geometry for real-world entities, such as walls, columns, and large equipment; or obtain an optimized model by cropping and reducing the faces of the Block dense model.

  • Runtime alignment: at runtime, align the Block coordinate system with the real space through cloud localization and load the corresponding geometry.

  • Material replacement: assign special occlusion materials to these geometries.

  • Visual effect: when the GPU renders other virtual objects, pixels in occluded parts are automatically culled because they fail the depth test, making virtual objects follow the occlusion logic of the real physical space.

Use mask files from mapping results

Follow the steps below to download the mask file from the mapping result through the Mask file download entry of the cloud localization database, use it as an occlusion white model, and import it into the scene. The mask file can be used directly or cropped as needed.

Note

This download method applies only to mapping results from mapping version 9.6 or later.

Download the mask file

After adding the Block to the cloud localization database, click Mask file download in the Action column of the row where the Block is located.

Mask file download entry

In the popup, select standard precision or low precision as needed, and click the corresponding Download button to download the mask file in glb format.

Download mask file

[Optional] Crop the model

The mask file covers the entire Block. If its coverage already meets the occlusion requirements, use it directly and skip this step. If only part of the area is needed for occlusion, crop it as follows.

Open the downloaded model in digital content creation software, such as Blender.

Before cropping

Crop the model, keep only the part needed for occlusion, and save it in glb format. Keep the model position, rotation, and scale unchanged during cropping so that it aligns with the Block after being imported into Unity.

After cropping

Import the model into Unity

Import the model into Unity and mount it under the corresponding Block node in the scene as a child node.

Note

Importing a glb model into Unity requires the com.unity.cloud.gltfast package, version 6.8 or later. If this package is not installed in the project or its version is too low, install or upgrade it through Package Manager.

In the Inspector panel, modify the Transform of the occlusion model and set its position, rotation, and scale relative to the Block node:

  • Set Position to (0, 0, 0).
  • Set Rotation to (0, 180, 0).
  • Set Scale to (1, 1, 1).

After this, the occlusion model should fit the corresponding part of the Block dense model.

Import occlusion model

Note

The mask file downloaded from the cloud localization database uses a different coordinate system definition from Unity, so the Y component of Rotation needs to be set to 180 for alignment. This setting applies to the mask file downloaded from mapping results in this section. Dense models exported through the Mega editor tool later use a different rotation setting.

Assign an occlusion material to the model

Change the model material to an occlusion material. You can use Unity's built-in SpatialMappingOcclusion.

Replace occlusion model material

Simulate running with EIF data or run on a real device

Use EIF data simulation or run on a real device to check whether virtual objects are occluded by the corresponding real-world areas.

Use geometry as occlusion

Follow the steps below to add geometry used as occlusion in the scene and verify the effect.

Place occlusion geometry

According to the dense model of the Mega Block, use built-in geometry or custom geometry as occlusion and place it at the correct position in the Block coordinate system. Place occlusion geometry

[Optional] Fine-tune the geometry position according to the panorama

Fine-tune occlusion according to the panorama

Assign an occlusion material to the geometry

Change the geometry material to an occlusion material. You can use Unity's built-in SpatialMappingOcclusion. Fine-tune occlusion according to the panorama

Simulate running with EIF data or run on a real device

Fine-tune the placement of the occlusion model according to the running effect.

Use a cropped and reduced dense model as occlusion

Follow the steps below to crop and reduce the exported Mega Block dense model to obtain a white model for occlusion, then import it into the scene as occlusion.

Export in Mega Blocks

Click the Export button to the right of Mesh to export the dense model.

Export dense model

Modify export options

Pay attention to modifying the export options when exporting.

In the figure, 1 is the LOD level. The lower the level, the simpler the model and the fewer faces. If you need the highest precision, select the highest level.

In the figure, 2 is the texture export option. Here only the white model is needed as occlusion, and textures are not needed.

Crop and reduce the model

Crop and reduce the exported model in digital content creation software, such as Blender, and save it in glb format.

Tip

The example uses Blender's Decimate Modifier.

Before cropping

After cropping and reduction:

After cropping

Import the occlusion model into Unity and mount it under the Block node in the scene

Note

Importing a glb model into Unity requires the com.unity.cloud.gltfast package, version 6.8 or later. If this package is not installed in the project or its version is too low, install or upgrade it through Package Manager.

Import occlusion model

Modify the model Transform

Modify the model's Transform so that both Position and Rotation are all 0.

At this point, the white model used for occlusion should fit the dense model, because cropping and reduction in the digital content creation software did not change the definition of the Block coordinate system.

Occlusion model fit

Assign an occlusion material to the model

Change the model material to an occlusion material. You can use Unity's built-in SpatialMappingOcclusion.

Replace occlusion model material

Simulate running with EIF data or run on a real device

Simulate running with EIF data or run on a real device to view the effect.

Expected occlusion effect

The occlusion effect is mainly affected by the following:

  • The accuracy of localization tracking itself
  • The accuracy of model placement
  • The accuracy of the model itself, if it is not simple geometry

It is normal for several centimeters of misalignment to occur during localization drift.

Too many faces in the occlusion model can easily affect performance. It is recommended to use it only in necessary areas and use simple geometry as occlusion as much as possible.