Zdepth

[shkumbin]

Hello guys,
I have been having troubles with this, sorry if its a dumb question but I just dont know how to get around it.
For instance I have a scene with 3 objects, 1 os 1 m far, the other 2 m and the other 3 m, now I want my focus to be in 2 m, How can I control this on zdepth? I am using normal max camera, whenever I render a zdepth, it only defocuses things in distance far away, but how do I actually specify to blur everything that isnt in focus in this case in 2 m, which would mean both the 1 m and 3m far objects would have grey color while the one in 2m would be white?
Cheers

[vlado]

How do you do the defocusing (e.g. what program are you using)? Some programs allow you to pick the point that you want to be in focus directly from the z-buffer itself.

Best regards,
Vlado

[shkumbin]

How do you do the defocusing (e.g. what program are you using)? Some programs allow you to pick the point that you want to be in focus directly from the z-buffer itself.

Best regards,
Vlado

I am using saphire defocus for After effects, it works very well, but I need the zdepth image to be properly created in vray, so I have the gradient as I need, so all I need to do is apply the defocus and not play with the focal etc in the post cus usually it messes it all up. I mean isnt there any way that I can specify somehow the focal point and the zdepth information will be stored accordingly. I am using .png format to save the files out.

[mike_kennedy]

Zdepth is generally Fixed in Meters specified in the Render Elements area and then you use the plugin to change the focal point in AE, We use another DOF plugin for AE (Lenscare) and it supports this and every one I have tried, except for the Saffire one you are mentioning (have not tried that one) supports this...

[stevesideas]

Im not sure if I understand you correctly but it sounds like you want to define a zdepth distance, between the nearest object and the furthest. The way I do it is to draw a spline. Pick a point at the camera centre and then draw to the nearest object. You can read off the distance down the bottom left of the max window. So that becomes your near distance. Then draw another line and get the distance to your furthest object. That distance will become your max distance. Enter these min and max values in the zdepth min and max values. When you now render your zdepth it should be correct - with near things in white and further objects becoming darker.

With this zdepth map you should then be able to pick a point using your DOF plugin and it will set the focal point to that point.

[shkumbin]

well I understand u completely but it doesnt appear that vray zdepth works in that way, what it does it always makes the furthest objects to the camera darker no matter what ur focal point is, which is wrong, because it should make the close to camera objects which arent in focal point too darker and therefore the middle one which is in focal whiter. Thats how the vray DOF works , and when I try the plugin in After effects to change the focal point it does it but it always keeps 2 objects in focus, not only 1.

[shkumbin]

Ok I think I have solved it, the plugin is capable of adjusting the focal point correctly it just needs some careful tweaking. I would of course still prefer if there was a way to get the correct image out of vray though.
cheers everyone

[stevesideas]

Have you tried unchecking the invert zdepth in the vray elements rollout...not sure if thats what you mean...

[shkumbin]

Have you tried unchecking the invert zdepth in the vray elements rollout...not sure if thats what you mean...

I would assume that would be just inverting the colors of the gradient, which u can do in post as well, also the plugin mentioned earlier can do it.
I haven't tried it .

[stevesideas]

I think I understand where you're coming from now, but Im not sure that is correct. Zdepth will always be a single gradient type image, with the image either going from white to dark or the reverse. Assuming you pick an rgb value on the zdepth map of 128, everything either side of this value will start to become defocused until you reach 0 and 255, where the defocus will be maximum. Im not sure how your plugin works, but every other plugin works the way I just mentioned...tell me if im wrong someone...thats from my personal experience.

[mike_kennedy]

ALl DOF Plugins I have used work this way. I understand what he is asking for but it kind of defeats the purpose of doing DOF in post.
My guess is that he needs to increase the depth in Meters (or his system unit) so he hasa a wider range to play with. A really short DOF range is tricky to work with.
Cheers
Mike K

[stef.thomas]

Z depth is merely an image based on objects distance from the camera it has nothing to do with focus or the depth of field in itself. As has been said before most plugins (DOF Generator for Photoshop e.g.) or programs like Combustion use this data to add depth information to an otherwise flat image. They then use this data to allow you to define focal distance and depth of field. It is more sophisticated than just a straight gradient from in focus to out of focus. The Z depth is just a part of the process, in other words the software determines the focal aspects of the image, not the z depth pass.

[shkumbin]

yea i got that now, cheers