[vtkusers] Z-buffer to Depth: formula

[Wes Bethel]

Check out the OpenGL vertex transformation web page: 
http://www.opengl.org/wiki/Vertex_Transformation

In brief, you need to know the specifics of the view (camera) and any 
world-coordinate transformations, along with the exact values for the 
near/far clip plane, in order to compute, from a z-buffer value, a 
depth-from-the-viewpoint (eye) in either eye or world coordinates. It is 
likely these complexities/details that prevent someone from handing you 
a chunk of code to compute it.

I've personally written code to do this in the past, but focused on 
doing depth-from-viewpoint in eye coordinates to avoid the snake-pit of 
world coordinate system transformations.

Your best bet is to look at the URL above so that you can construct the 
conversion formula yourself given whatever your specific needs are.

HTH,
wes

On 12/9/11 6:39 AM, Dženan Zukić wrote:
> 0 corresponds to near clipping plane, and 1 corresponds to far clipping
> plane. If you know the distance of both you can do linear interpolation.
> Someone correct me if I am wrong.
>
> On Fri, Dec 9, 2011 at 07:41, Atul Kumar<sharmaatul11 at gmail.com>  wrote:
>
>> Thank you so much David. I will try vtkRenderer::ViewToWorld().
>>
>> To Dev
>>
>> vtkRenderer::GetZBufferData() gives us the depth map values which ranges
>> from 0 to 1, so it is not the actual depth value at the pixels. To get the
>> actual depth at pixels we need to convert Z-buffer into actual depth
>> values. So, for this we need a conversion formula. I hope this makes it
>> clear.
>>
>> Regards,
>> Atul
>>