Depth map accuracy about bpycv

[hansongfang]

The depth (z-buffer) of blender are orthogonal distance to lense's plane. Did you calculate depht like this?

Thank you for sharing this great tool. I observe that for blender 2.81, the cycles engine does not output z depth buffer as orthogonal distance to lense's plane. Actually, the z-buffer is the distance from the camera to pixels, as mentioned by @yushiangw. But on blender 2.93, it outputs orthogonal distance. For users using blender 2.8x with cycles engine, they should be careful with the depth map.

[yushiangw]

It looks like switching to CYCLE + shift image coordinates by 0.5 help. I thought camera clip_end/start will make some difference but not much.
https://docs.blender.org/api/current/bpy.types.Camera.html#bpy.types.Camera.clip_end
some of my numbers :

BLENDER_EEVEE 
mean_dist  =2.75e-04
median_dist=2.56e-04
max_dist   =1.24e-03
min_dist   =1.94e-06

BLENDER_EEVEE + set clip start/end to (0.5,5)
mean_dist  =2.73e-04
median_dist=2.51e-04
max_dist   =1.24e-03
min_dist   =1.94e-06

CYCLE   
mean_dist  =7.46e-05
median_dist=3.34e-05
max_dist   =1.21e-03
min_dist   =8.67e-09

CYCLE + set clip start/end to (0.5,5) + add 0.5 pixel shift
mean_dist  =8.40e-08
median_dist=3.62e-08
max_dist   =1.31e-06
min_dist   =5.20e-12

CYCLE + add 0.5 pixel shift
mean_dist  =8.12e-08
median_dist=3.52e-08
max_dist   =1.35e-06
min_dist   =5.20e-12
```

[DIYer22]

The depth (z-buffer) of blender are orthogonal distance to lense's plane. Did you calculate depht like this?

[DIYer22]

I found the same error.
In my case, the depth should be 1.38831, but got 1.3876953125.
Which shorter 0.0006146875.
And I have no idea what is wrong. 😢