Depth Buffer

[Peter Paterson]

Guys

I'm having a real problem in getting a depth buffer out of LightWave using exrTrader.  I am certain it is me that is missing something.

For example if I chose to view the z buffer using the render buffer view...well there it is, I can see it in the when I view the buffer using LW's viewer.  Yet when I choose to use exrTrader, the depth buffer, as viewed within viper is a black image of the object on a white background (Raw Bufer Normailised View).

Please, if you can shed som ehelp on this then I will be very grateful.

Thanks

[lightwolf]

Hello Peter,

this is a snipped from the manual for the next release (which is in beta), where we've gone into more detail about the buffers that LW provides (mind you, exrTrader doesn't generate them, it also doesn't change them if the processing options are at their defaults):
Depth
This buffer stores the distance of a surface from the camera.
Due to the fact that the depth is stored as a proper float image and the pixels represent the distance to the camera in metres, there's a few facts to remember.

The first image to the right shows the normalized depth buffer for the sample render. There isn't much to see because the top of the image is the backdrop. In LightWave the backdrop is always rendered at an infinite distance1.
A normalized view looks at the highest and the lowest value in an image and then tries to display anything between them in the visible range from 0.0 to 1.0. In this case the backdrop compressed to be at 1.0, and all other values are compressed respectively. This means that the actual items are relatively close to the camera (at least in relation to the backdrop) and thus displayed as being black (which corresponds of a distance of 0, or something very close to it).
If you intend to composite in an application that handles float images (and the tools that are used to actually work with a float depth buffer) then there should be no need to change anything.

If you intend to save the depth buffer as a low dynamic range image then you can use the Minimum and Maximum settings to define a range which should be normalized into the visible range.
The second image illustrates this, it is the same depth buffer as in the first image, but the Maximum has been set to 10.0.
One caveat, in the last release (V1.3) the minimum/maximum settings don't work as described here for the depth buffer (this is fixed in the next release).
Until that time you should use scale instead, using a low number (basically 1/<max distance in the scene>, i.e. 0.1 for a range from 0 to 10m, 0.01 for a range of 0 to 100m).

I hope this helps understand the depth buffer a bit better.

Cheers,
Mike

[Peter Paterson]

Hi Mike

Thanks for this clear explanation.  I will play about with this tomorrow and get back here to comment. 

Cheers

Pete

[Peter Paterson]

Just played about with the scale function, and this works as expected, thank you.  Also...I never realised that the scale setting can be set interactively with Viper open, brilliant

[lightwolf]

Also...I never realised that the scale setting can be set interactively with Viper open, brilliant

Oh yeah, I love that bit as well. You should have seen me giggle once I had it in place and played with it for the first time.

I also want to add a picker/info window in a future version of exrTrader, that allows you to click on the VIPER image and then displays the pixel values numerically in a small window for diagnostics.

Cheers,
Mike

[Peter Paterson]

Oh yeah, I love that bit as well. You should have seen me giggle once I had it in place and played with it for the first time.

I also want to add a picker/info window in a future version of exrTrader, that allows you to click on the VIPER image and then displays the pixel values numerically in a small window for diagnostics.

Cheers,
Mike

That will be very useful...thanks for all your work on this.

[lightwolf]

That will be very useful...thanks for all your work on this.

Well, thank you for supporting us

Actually, the list of stuff we'd like to implement is usually quite large. The hard part is picking the stuff to work on and finding a way to do it properly.

Cheers,
Mike

[Peter Paterson]

The hard part is picking the stuff to work on and finding a way to do it properly.

I'm sure you guys will find solutions

Cheers

[lightwolf]

I'm sure you guys will find solutions

Hehe... that's all coding is... finding solutions to problems we wouldn't have without computers

Cheers,
Mike

[Peter Paterson]

Ah...insight can be a dangerous thing! 

[lightwolf]

Ah...insight can be a dangerous thing! 

Yup, but life wouldn't be the same without danger

Wow, that's why it's called the Depth buffer - or should it be shallow buffer?

Cheers,
Mike

[Riff]

Lightwolf:

Although I purchased exrtrader some time ago, I have just now had the time to begin to use it.  My pipeline is LW9.6 (build 1539) & Fusion 5.31 (build 78).  Both apps are the 64bit versions using XP64.

Wow, exrtrader is very well thought out.  Lightwolf repeatedly describes himself as being "picky".  That is good, very good in that this little plugin works so well.  That being said, I also was having problems getting the zbuffer to actualize in Fusion.  This thread provided a solution (use scale) which I would not have been able to 'discover' for myself.

Also note that Timothy Albee posted a LW/exrtrader/Fusion pipeline tutorial on Spinquad.  Just what I needed, URL as follows:
http://www.spinquad.com/article/story/8&page=1

Oh, btw, Lightwolf, I miss your presence on IRC (freenode: #lw3d)

Riff Masteroff

[lightwolf]

Wow, exrtrader is very well thought out.  Lightwolf repeatedly describes himself as being "picky".  That is good, very good in that this little plugin works so well.  That being said, I also was having problems getting the zbuffer to actualize in Fusion.  This thread provided a solution (use scale) which I would not have been able to 'discover' for myself.

Thanks As I mentioned before, the manual for V1.4 will contain more information on how LW provides the buffers, and what it provides.
Here's a sneak of the re-vamped GUI:

Also note that Timothy Albee posted a LW/exrtrader/Fusion pipeline tutorial on Spinquad.  Just what I needed, URL as follows:
http://www.spinquad.com/article/story/8&page=1

We also link to that (in our apparently well hidden) links section on the website

Oh, btw, Lightwolf, I miss your presence on IRC (freenode: #lw3d)

It kept kicking me out and annoyed me... I'll try to stick around more though.

Cheers,
Mike