Question about z-depth render element

[Seila]

hi,

I need an information about the distance from a front-view camera to object so i add a z-depth render element when rendering. However the results are not as expected since the value of pixels not represent the depth distance(The scene with max and min depth distance is 12 and 0 ), they just repsent some values around 0.004~0.006. what the z-depth value stand for and how could i get the desired depth information using render element ?

Another question related to this issue is when choosing the output format i see a "exr(deep)" option and the result of z-depth render element is slightly changed when changing output format from "exr" to "exr(deep)". What's the difference between these two types of output ?

[Zdravko.Keremidchiev]

The Z-Depth values that you get are relative to the Max/Min depth ones. In case you want to use the z-depth for distance information it will be best to set those values to 0/100 or 0/1000 depending on the scene size. This way you would get comprehensible distance information.
Also, the deep format image files contains additional depth information ("each pixel in a deep image can store an arbitrary number of values or samples per channel. Each of those samples is associated with a depth, or distance from the viewer. Together with the two-dimensional pixel raster, the samples at different depths form a three-dimensional data set. ") which is used for composting purposes. In case you do not plan to take advantage of the Deep composing after rendering it will be best to use regular exr files.

[Seila]

hi Zdravko,

Thanks for you reply and finally i find the parameter appears in VRayRenderElement Node (i expect it would embedded in render setting window). I thinks the parameter "VRay Depth Black" and "VRay Depth White" is the Min\Max parameter. There're some parameters that i can't guess it's functionality by parameter's name:
- Depth clamp (Since Max\Min already set, is there anything else need to be clamped ?)
- Use depth from the camera (If unchecked this, what's the meaning of result ?)
- Out Connect

Could you provide more details about these parameters ?

[Zdravko.Keremidchiev]

Yes, by Min/Max I meant VRay Depth Black/White options.

- Depth clamp (Since Max\Min already set, is there anything else need to be clamped ?)

Yes, the Depth clamp will clamp everything beyond the VRay Depth White value to one. In case you are using floating point format you can leave this option disabled and have information for the objects which are far from the define maximum.

- Use depth from the camera (If unchecked this, what's the meaning of result ?)

If you already set Near/Far Clip plane in the Camera menu you can use them instead.

- Out Connect

This option is not available. Please ignore Extra Attributes roll-out menu, the one that you need is Extra V-Ray Attributes.