D455 the coordinate system
Looking at the D455 camera model from the front, the order from left to right is: Right Infrared sensor, RGB sensor, Infrared Projector and Left Infrared sensor.
I want to understand the direction of the coordinate axes, in particular for the RGB sensor. The z-axis always points forward and y-axis points downward, but I am confused with respect to the x-axis. It points to the right, but from the perspective of the camera or the person? Please can you help with a simple diagram. thanks,
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Hi Zahid Iqbal The D455 camera model uses the same coordinate system as the D435i, described at the link below.
RealSense sensors use the perspective of a person standing behind the camera looking forwards, like a person's eyes looking forward at the real world. This is why when the camera is viewed from the front, the left infrared sensor is on the right side of the camera.
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There is an easier way to visualize how the coordinate system works. Depth and RGB color each have their own separate 3D coordinate systems. In these systems, the positive x-axis points to the right, the positive y-axis points down, and the positive z-axis points forward.
Whether the X and Y coordinates are positive or negative depends on whether a coordinate is to the left or right of the center-line of the sensor (X), or above or below the center-line of the sensor (Y).
So if a coordinate on the image is in the top left area of the RGB image then you could say that its Y coordinate value is a minus value (because it is above the RGB sensor's centerline) and its X value is a minus value (because it is to the left of the RGB sensor's centerline).
It is a somewhat difficult subject, and one that usually does not have to be thought about at all when creating RealSense applications. I believe that the confusion may stem from the above diagrams being viewed from the front-of-camera perspective, when the camera actually uses the 'standing behind the camera' perspective. So when viewing from behind looking forward, what is positioned horizontally right on the front of the camera becomes left.
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