[Amira 3D, Avizo 3D]
Issue & Reason
For background, Avizo 3D renders 3D images using the OpenGL graphics API.
Running two overlapping Volume Rendering modules simultaneously is not officially supported. This limitation exists because OpenGL does not properly support this type of 3D representation. The application normally prevents this configuration by disallowing the creation of two Volume Rendering modules for the same dataset.
Users may attempt to circumvent this restriction to visualize multiple datasets or rendering effects simultaneously. While this may be technically possible, it is considered unsupported usage and may result in suboptimal or incorrect rendering.
Because this configuration falls outside the supported use of the software, no official documentation is available for this specific scenario.
Suggested Solutions
- Use surface rendering together with a single Volume Rendering module
A practical approach is to combine surface rendering with a single Volume Rendering module. Some interactions between shadows and transparency may not render correctly. However, this approach provides a practical way to visualize two datasets simultaneously.
1. Attach an Isosurface Rendering module to the dataset, define the appropriate threshold value, and apply the module.
2. Attach an Isosurface Rendering module and define the threshold.
3. Create a surface using Generate Surface and display it using Surface View.
Refer to the article KA-01376 / How to Generate and Simplify a Surface.
- Use a shared clipping plane
You can also use a shared clipping plane between two Volren (or Volume Rendering) modules. For detailed instructions, refer to this tutorial: How to Set Up a Two-Sided Clipping.
- Use Interactive Thresholding with 3D Preview
Attach an Interactive Thresholding module and enable Preview Type > 3D. Adjust the Intensity Range to control which parts of the volume are displayed.
- For versions prior to 2025.1
1. The most common workaround is to use the Volren module. It relies on a different rendering pipeline than Volume Rendering. However, the rendering is less accurate and may not be suitable for your application.
2. If you want to use two Volume Rendering modules with the same dataset, you can do so using the Tcl console:
2.1 Open the Tcl console by clicking the ">" icon on the lower-right corner of the interface.
2.2 Create an additional Volume Rendering module and its corresponding Volume Rendering Settings module by running the following commands:
create HxVolumeRender2
create HxVolumeRenderingSettings
2.3 Two unattached modules will appear in the Project View. Connect the Common Settings port of the Volume Rendering module to the Volume Rendering Settings module.
2.4 Connect the Volume Rendering Settings module to the desired dataset.
This procedure bypasses the GUI restriction that prevents attaching two or more Volume Rendering modules to the same dataset.
Related Link
Xtra: How to Visualize 3D Image Data