Rendering Depth Maps.


#1

I’m just starting to explore adding fog, DOF, etc. effects in post rather than waiting for them to render in LW.

What are the best ways to get a good, clean depth map out of LW?


#2

check out all the available render buffer exporters. there’s one native in lw, as well as several plug-ins on flay. use the one you like best.


#3

Some people like to use the buffer exporters. Not me. I usually create a depth-map by creating a shader (black and white gradient controlled by distance from camera) and apply it to all objects in a scene. I find it gives a good amount of control and is great for getting immediate visual feedback from test renders (even better if you’re using F-Prime).


#4

I just turn down global light intensity to 0, change backdrop color to white, add backdrop fog.


#5

Thats acually the method I came up with a bit ago.

I use nulls with range finders attached that tell me the furthest point in the scene to the closes point in the scene and use those numbers to set the limits for white fog.

It works well enough in photoshop CS… but I was curious about the other programs out there that actually use z-depth information.

thanks for the replies.


#6

http://www.dougplanet.com/tut-rla-fun.html

one i’m aware of, for the .rla format and use by after effects.


#7

The problem with the depth buffers is that they don’t get antialiased…so when you use them to apply blur in post, they never really quite match up right. I usually just do the black object in white fog trick (I find it easiest to just make everything a black matte object and then apply white linear fog). Then it’s a simple matter to use the luminance of this sequence to control the amount of blur to be applied in something like Fusion or AE.


#8

LW8 has an option (Render Panel) called Deph Buffer AA; allows to export Deph Buffer with antialiasing. (and I think LW7.5c too, but I don’t know where is that option)

Gerardo


#9

Ah…I see…I’m still on 7.5. I’d be curious to know if that actually works well or not…have you tried it, gerardo?


#10

No, sorry; I haven´t tried it yet (I use xDof :thumbsup: ) but I needed it some months ago for a high resolution illustration that should be composite with other elements, I read in the manual (update 7.5c) this option is included, but I don’t still find it. Finally I made it exporting the Z-Buffer (RLA format) and using Depth Matte and Gaussian Blur on AE.
LW8 includes it in the render panel, I´ll test it today. :slight_smile:

Gerardo


#11

If I remember correctly Asa_BufferSaver gives out normalized z buffer with correct reflection values instead of the buggy ones LW outputs as default.


#12

the only way i do that is with fog - like you said. All the exporter buffers /Depth channel/ are not usable because they don`t have antialiasing added on them.

Gerardo that AA on Depth buffer is not exactly what you assume. I was very happy with it until i found that it doesnt work. And not only doesnt work, but in the help file i can`t understand a damn thing from that passage:

The passage is from the Camera Basics introduction:
Depth Buffer Antialiasing
The Depth Buffer Antialiasing command (Effects command group) has been added to specify how the Z-buffer values from multiple antialiasing passes should be combined when creating a final depth buffer for output. Executing the command will display a small dialog. The Minimum Value setting (the standard behavior) causes each pixel to store the closest of the depths found at that pixel in all passes. The Average Value setting causes each pixel to store the average of the pixel’s depths in all passes. The Depth Buffer Antialiasing setting is not saved with the scene, so you will need to enable it each time you set up a render. This also means that it cannot be used with a network render.”

So i continue to use simple fog pass with antialiasing.


#13

Well that just screws the pooch for me right there. If it’s not network renderable, forget it. :hmm: Still, it might be interesting to play around with when (if) I ever decide to upgrade to 8.

I think I kind of understand what that quote refers to…in that if you have an object that’s close to you so that it renders black, and the background is white, the edges of the black object, upon antialiasing, will turn a shade of grey…which is technically not correct, so this plugin apparently gives you the option of having the antialiased edges take the value of the pixel near it which is closer to the camera (in depth value), the one which is further away, or an average of the three.

Basically…in practice, while doing the fog trick might not technically give accurate results, it sure looks a helluva lot nicer than using a “real” depth pass with big ugly jaggies everywhere. :argh:


#14

In Tim Albee’s book about making Kaze Warrior, he recommends rendering out the frames without AA but at twice to normal size. Then use those for your post-effects and then reduce it to the correct resolution and that creates a cheat on the AA in the final


#15

That’s true…you could do that. I guess it’s something you need to evaluate on a per-shot basis, which method suits your needs better.


#16

Hi Scroll_Lock, you are right about that it cannot be used with a network render, but the tool works very well (at least here). I´ve just tested it, and initially (with only one object) it didn’t work; the trick is to put a flat polygon behind the object that you will render (100% transparency if you want) that´s all, Depth Buffer antialiased. :slight_smile:


Gerardo


#17

So the rla export plugins do not work in network rendering…or is it just depth aa settings.

Gerardo …fantastic picture. Is that LW8?
How did you do the textures? Did you photo reference or hand paint them. If you painted them…WOW!


#18

Just the Depth AA filter. I’ve used the RLA/RPF export many times with a network render, and it works just fine.


#19

Thanks Jules!!! :slight_smile:
Yes is LW8. Surely some excellent texture artist in this forum can make it by hand, but at less for me its very difficult; I made it with reference photos , you scan 4 sides of a real jar and merge them in PS; for the interior part, cut a bristol board with the jar perimeter and slap it in the interior until the bristol board is daubed with painting, then extended the bristol board and wait until it dried off to scan it. I split to CMYK all these images to obtain the bump, difuse and specular channels. The illumination is two spinning lights rigs. However I like more with xDof, the render difference is only half minute (LW7.5c):

Gerardo


#20

I´ve just tested it, and initially (with only one object) it didn’t work; the trick is to put a flat polygon behind the object that you will render (100% transparency if you want) that´s all, Depth Buffer antialiased.

Sorry for bringing this thread up. I tried Gerardo technique using a flat transparancy polygon in front of the camera to get the Depth Buffer Antialiased… Export the RLA with depth map, with Depth Buffer AA. I used Depth of Field in AE however seems that AE can’t find the depth map… Did i miss something??

PS: It works properly without the flat transparancy polygon.

Thanks