Intel RealSense D455 Blotches
Hello,
I'd like to understand a phenomenon in the RGB and Depth streams of the Intel RealSense D455.
There are large black blotches in both streams, when in 3D mode; when I switch to 2D, these are only present in the depth stream.
Below (in order): 2D tile view; 2D depth; 3D RGB; 3D depth
I've looked at other threads for non-D400 RealSense products, and it looks like these are "shadows" caused by the stereo format of the infrared imaging system. Is the same thing happening here? I understand that the IR sensor on the D400 is not a stereo system, so I'm wondering why the same phenomenon is occurring.
Thanks!
Andrew
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Hi Andrew John Madey All of the RealSense 400 Series camera models are stereo depth, because depth is constructed from left and right infrared sensors (hence the 'stereo' term).
When switching to 3D pointcloud mode and enabling depth and RGB, the RGB data is mapped onto the depth coordinates to create a combined image (a textured pointcloud). So if there are black gaps in the depth image then these will also appear on the combined depth + RGB 3D pointcloud image.
The black outline around the ceiling fan is likely caused by a phenomenon called occlusion where a black outline appears around objects due to the camera's infrared and RGB sensors being at different physical positions on the front of the camera.
The rest of the black gaps may be due to those areas of the scene being just out of range of the camera's depth sensing. Although the D455 is capable of long range depth sensing, the RealSense Viewer may apply a 'post-processing' filter called a Threshold Filter by default. This filter, which allows the definition of a minimum and maximum depth sensing range and excludes depth coordinates outside of that min-max range, is set to 4 meters maximum by default.
Please expand open the Stereo Module > Post-Processing section of the Viewer's options side-panel to view a list of post-processing filters. If there is a blue icon beside Threshold Filter (indicating that it is enabled), left click on the blue icon to turn it to red (disabled) so that the full range of depth data that is visible to the camera can be rendered on the depth image.
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Hi Marty,
Thank you for your help. I think I was confused re: the stereo depth sensing, as I only saw a single IR sensor on the camera, but did not look at things sufficiently closely.
I think I am missing a comprehensive understanding of the RealSense software interface (free of code - just the settings that can be manipulated by way of the window), and am wondering where such an overview might exist. I think that would help me understand things a bit more systematically, and therefore know better how the data itself is collected, displayed, and manipulated. Do you know where I could find such an overview?
Thanks!
Andrew
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There are a wide range of video guides on the official RealSense YouTube channel.
https://www.youtube.com/c/IntelRealSense/videos
Of those videos, the guide to the RealSense Viewer would be a good place to start.
https://www.youtube.com/watch?v=BVM1wxE9x0E
There are also a wide range of white paper guide documents.
https://dev.intelrealsense.com/docs/whitepapers
The white paper guide to tuning 400 Series cameras is the best place to begin learning how to adjust settings.
https://dev.intelrealsense.com/docs/tuning-depth-cameras-for-best-performance
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