Yes, it's worth taking note of that and it's caught me out in the past. If you take the vector from the camera position to any position coordinate in the scene you're getting the true distance, whereas a Zdepth image is just the z component of that distance.
I've found the easiest way is to do a coordinate system transform from world space to camera space then just take the Z channel. Note that, depending on the shutter angle of the render vs the imported camera keyframes that you may get a minor offset compared to rendering "in camera". Michael On 13 May 2013 09:41, Eetu Martola <[email protected]> wrote: > Most renderers write Z as orthogonal distance to the (extended) > cameraplane, instead of the actual distance between the pixel position and > camera center point. Is your perceived difference greater toward the image > edges? > > eetu. > > > > On 13.5.2013 16:36, Steve Newbold wrote: > >> Pixel perfect compared to what? A depth pass from the same render as >> the world position pass? >> >> How far off are your values? Can it be put down to rounding of the >> camera position from your 3D package or rounding on the pass values. Is >> your depth pass 32bit float? Other things to check are premultiplcation >> of the position pass from the renderer. >> >> Steve >> >> >> On 13/05/13 14:26, Simon Björk wrote: >> >>> Hi all, >>> >>> I'm looking for a way to accurately converting a point position pass >>> (world space) to a depth pass (camera space). I have a camera available. >>> >>> The following expression gets me close but not pixel perfect: >>> >>> set cut_paste_input [stack 0] >>> version 7.0 v4 >>> push $cut_paste_input >>> Expression { >>> temp_name0 cx >>> temp_expr0 shot_camera.translate.x-r >>> temp_name1 cy >>> temp_expr1 shot_camera.translate.y-g >>> temp_name2 cz >>> temp_expr2 shot_camera.translate.z-b >>> temp_name3 dist >>> temp_expr3 sqrt(cx*cx+cy*cy+cz*cz) >>> channel0 rgba >>> expr0 dist >>> channel1 none >>> name Expression7 >>> label "convert p world to z-depth" >>> selected true >>> xpos 266 >>> ypos -50 >>> } >>> >>> >>> >>> ______________________________**_________________ >>> Nuke-users mailing list >>> [email protected].**co.uk<[email protected]> >>> ,http://forums.**thefoundry.co.uk/ <http://forums.thefoundry.co.uk/> >>> http://support.thefoundry.co.**uk/cgi-bin/mailman/listinfo/**nuke-users<http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users> >>> >> >> >> >> ______________________________**_________________ >> Nuke-users mailing list >> [email protected].**co.uk<[email protected]>, >> http://forums.thefoundry.co.**uk/ <http://forums.thefoundry.co.uk/> >> http://support.thefoundry.co.**uk/cgi-bin/mailman/listinfo/**nuke-users<http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users> >> >> > ______________________________**_________________ > Nuke-users mailing list > [email protected].**co.uk<[email protected]>, > http://forums.thefoundry.co.**uk/ <http://forums.thefoundry.co.uk/> > http://support.thefoundry.co.**uk/cgi-bin/mailman/listinfo/**nuke-users<http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users> >
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