[Ernesto]

The Z channel map can be set from a desired distance to another desired distance. In this way you can have better gradient where you expects to do the posprocessing.
In Maxwell Z Channel darker means nearer, and clearer means far.
The problem is that everything which is behind the far limit of the Z channel area, should be white, but is black.

Ernesto

[tom]

I try this but it gives me white if it's nearer and black if it's farther. Can you give an example output?

[Ernesto]

Yes Tom, but it could be that way or it could be exactly the oposite, within the Z range, deppending which part of the image you are looking at.
Anyway outside of the Z range it looks inverted.
This is prety crazy in some parts of the image!
For instance, the main building entrance is nearer the camera, than the top of the building, and the near part is clearer in relationship with the top which is darker!
But if you look at the trees in the foreground they are nearer the camera in relationship with the building, but they are darker...

I will describe it in detail, how I was expecting it to work.
Let,s assume I set the Z channel to work from 6 meters to 20 meters.
This will produce an image where an object at 6 meters will be black, and an object at 20 meters will be white, while everything in between 6 and 20 meters will be grey.
Now if you have objects out of the Z channel range, for instance 30 meters, they should be white. In the same way, any object between the camera and 6 meters should look black.




Here I am posting 3 images, each of them with the Z range.
The last one which Z range should be from 18 m to 20 meters, should show everything from 18m to the camera as black, but it is grey.
In the same image everything behind the building should be white but it is black.
If you look at the first sample, you will see a hole in the image, part of a tree and the far left building have dissapeared, this is because they are behind the Z limit. The Z limit is 10 meters and everything from 15 meters and infinite is shown in this image a black, but as far as I understand this should be white.

I have 3 conclusions:
1) the near the camera Z limit does not work, it looks that it is fixed in zero.
2) the colours out of the Z range are inverted. There should be continuity in the full grey scale. But there should be detail within the set range. Out of the Z range there will not be detail, in other words it should be plain black and plain white, but I was not expecting a jump from white to black or viceversa as it is seen in the samnples.
3) there is a disorder within the Z range, some objects that are nearer the camera look darker and some other look lighter!? For instance, the balconies on the building are nearer the camera in relationship with the facade plane, and they are seen darker than the facade plane.
Up to now: dark=Near
But the facade plane shows a gradient, darker at the top, and lighter at the bottom.
Here the rule is Light=Near

Note: I have not much experience using Z channel maps, but this is the way other softwares creates them.

Ernesto

[Ernesto]

After watching the immages for some more time...
I think now I understand where is the error.

One option could be the following:
All distances are measured from the camera point.
This crazy Z Channel uses this rule in the horizontal plane:
Nearer= Darker
But in the vertical plane, it uses the following rule:
Nearer= Lighter
This has no sense and produces a contradiction that appears in the black hole.

Another theory could be:
The light loses at the corners of the image, produced by the so called "vigneting effect" is faking the Z channel data.

One thing that I cannot explain clearly is the Black hole.
What is bothering about it, is that it is not located at the end of the Z range nor at the begining of it, so, what is it?

Ernesto