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Hello, I'm trying to understand the figure,

1. I've noticed the SDK example that float *gaze = eye_data.verbose_data.left.gaze_direction_normalized.elem_;

Is the coordinate of right or left Gaze_Direction_Normalized as same as the coordinate where user is looking at?

If no, how to calculate the coordinate where the user is looking at?

2. I've read the comment that "The data `gaze_origin_mm` represents to your eye location and the origin point is in the middle of your HMD."

Is combined.eye_data.gaze_origin_mm equal to the combine gaze origin of the figure? but it's not always be (0, 0, 0)

Could I guess that the gaze origin is as same as the starting point of eye? I don't really know how this parameter works.

Thanks for helping me to understand this figure.

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1. Yes, gaze direction is used to calculate where the user is looking.

2. Yes, gaze origin is the starting point of gaze direction. As shown in the diagram, combined gaze origin is the same as the figure, but notice it's not the same position as the system origin.

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• 2 weeks later...

@Corvus Thank you very much for the replying!!

But I still have a few questions want to know:

1. I've noticed this figure(VIVE PTO EYE: use the "Right-handed coordinate system"), I guess it means that if the user is looking at the right, the x axis of right/left gaze direction would be +. I tested the results as the figure, if I didn't moved my head, looked at the right, but the x axis of gaze_direction was negative value, what does the (0,1)value and negative/positive value mean? how to interpret it?

2. Does the the figure of coordinate mean relative position with the HMD? How to interpret the coordinates of gaze_direction if user turn his/her way left/right?

3. Although I know that Gaze_Origin means the starting point of Gaze_Direction, I still don't know how to interpret the value, what does the (0,1)value and negative/positive value mean?

4. I know that the CombinedEyeData Struct is not supported yet, Is the Combine Origin equal to "eye_data.verbose_data.combined.eye_data.gaze_origin_mm.elem_;"? What does the (0,1)value and negative/positive value mean?

Thank you very much for helping me, I am looking forward to your reply.

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• 5 weeks later...

And I've noticed that the document describes the timestamp means "The time when the frame was capturing. in millisecond.",

6. Is timestamp comparable with the local time? I've converted the timestamp to local time, but it doesn't match.

7. Every time when I restart the headset, I get different value, would the headset's clock reset on every restart of the headset?

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On 8/4/2020 at 3:46 PM, nini613 said:

@Corvus Thank you very much for the replying!!

But I still have a few questions want to know:

1. I've noticed this figure(VIVE PTO EYE: use the "Right-handed coordinate system"), I guess it means that if the user is looking at the right, the x axis of right/left gaze direction would be +. I tested the results as the figure, if I didn't moved my head, looked at the right, but the x axis of gaze_direction was negative value, what does the (0,1)value and negative/positive value mean? how to interpret it?

2. Does the the figure of coordinate mean relative position with the HMD? How to interpret the coordinates of gaze_direction if user turn his/her way left/right?

3. Although I know that Gaze_Origin means the starting point of Gaze_Direction, I still don't know how to interpret the value, what does the (0,1)value and negative/positive value mean?

4. I know that the CombinedEyeData Struct is not supported yet, Is the Combine Origin equal to "eye_data.verbose_data.combined.eye_data.gaze_origin_mm.elem_;"? What does the (0,1)value and negative/positive value mean?

Thank you very much for helping me, I am looking forward to your reply.

• The eye gaze is from eye to outward, so +Z direction is from eye to outward. Thus you need to rotate the coordinate shown in your figure according to Right-handed system.
• (0,1) means the gaze vector is normalized to a unit vector.
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2 hours ago, nini613 said:

And I've noticed that the document describes the timestamp means "The time when the frame was capturing. in millisecond.",

6. Is timestamp comparable with the local time? I've converted the timestamp to local time, but it doesn't match.

7. Every time when I restart the headset, I get different value, would the headset's clock reset on every restart of the headset?

timestamp is is generated on the HMD. It would be be reset if to on/off headset.