Deciding between D435i and T265 for SLAM
I'm looking to purchase either the D435i or the T265 for a robotics application. I'd like some guidance/input as to which of the cameras to go for. Details about the application are below:
The camera will primarily be used for SLAM and navigation in an indoor environment such as an office space on a mobile robotics platform. The indoor environment will be expected to have floor to ceiling windows that provide the indoor space with variable lighting based on time of day, including direct sunlight at times. The host computer the camera will be connected to will either be an Nvidia Jetson Nano or Xavier running ROS2 Dashing. The chosen camera will also have a plexiglass pane in front of it for protection.
One of my main concerns is how the camera will perform with variable lighting ranging from complete darkness to sunlight directly hitting the sensor. I understand that for complete darkness, the D435i is the obvious pick since the T265 doesn't have IR capabilities. I also understand that direct sunlight is very difficult/impossible to deal with, but if one camera handled such a case better than the other, that would be preferable.
Another question concerning both cameras is if its possible to alter the camera parameters during operation. Through reading different forum posts, I found that the performance of the camera in different situations such as lighting depends on how parameters are set.
Specific to the T265 and its onboard V-SLAM, is it possible to have the T265 do its onboard V-SLAM while also being able to do object detection/avoidance on the host machine? Also, what exactly is meant by onboard V-SLAM? Does this mean the camera creates a map and sends it to the host machine? What the host machine sees out of the onboard V-SLAM is not clear.
Thanks for any help on making this decision.
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T265 questions such as your V-SLAM one are handled on the RealSense GitHub forum. You can post a question involving T265 there by visiting the link below and clicking the New Issue button.
https://github.com/IntelRealSense/librealsense/issues
Having said that, if you can only choose one camera or the other and not have both, the T265 would be unsuitable on its own for the described application. It lacks the Vision Processor D4 image processing hardware that the 400 Series cameras have inside them that allows them to auto-adjust to changing lighting in real-time. The T265 IR sensor also has an IR-Cut filter that prevents it from seeing the full range of visible light frequencies like the IR imager on the 400 Series can (as it has no IR-Cut filter).
Instead of a D435i, the new D455 would be a great choice. It has an IMU like the D435i, improved accuracy over distance by a factor of 2x compared to the D435 models, and has an improved hardware design that improves depth to color alignment. For the first time, the RGB sensor also has a fast global shutter like the depth does, and both RGB and depth have the same field of view (FOV) size.
Though pointing a 400 Series camera directly at the sun is not a good idea due to the risk of saturating the IR sensor with light, the depth analysis of the camera actually works even better in strong light.
Yes you can change the camera parameters during its active operation, either with your own program scripting or by changing options in the pre-made RealSense Viewer program.
You can purchase physical filters for the camera that can be overlaid on the lens and change the properties of the light entering the camera to customize its behaviour to your exact environmental needs if the default design of the camera presents challenges in the environment that it is operating in.
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Thanks for your quick reply. Unfortunately due to time constraints, I can't wait until the D455 model is available. From what it sounds like, the D435i is the way to go. I've got one follow-up question though: What kind of benefits would there be in getting both cameras and using them together apart from the obvious (better FOV on the T265, depth sensor and image processor on D435, etc.)? For example, would the two cameras be able to both feed the built in V-SLAM on the T265 (this might be another question for the GH forum)?
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It may be useful for you to watch Intel's 44 minute seminar on YouTube about using T265 and D435 together (see the 17 minutes 15 second point for the start of the part where the two together are discussed), and read the Better Together article, and then take questions to the GitHub.
https://www.youtube.com/watch?v=62vm0_RZ1nU
https://www.intelrealsense.com/depth-and-tracking-combined-get-started/
I apologise that I cannot answer your questions myself, as somebody else on the RealSenee team is responsible for T265 related questions. Good luck!
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