View Full Version : LW / DFX+ Depth Blur Problem

Robert Zeltsch
09 September 2003, 08:59 PM

I want to create a depth Blur effect in DFX+ with an LW generated rpf image. But when Im using the "Depth Blur Tool" in DFX+ I`m getting trouble with the borders of the objects. It looks like bad anti aliased.

I hope you can see what I mean.

After consulting the DFX manual, I think the problem is the wrong export of the "Z-Coverage Buffer" and the "Background R/G/ and B Buffers". How can I create these Buffers in a DFX compatible way with LightWave??

Thank you

09 September 2003, 09:06 PM
I've had to deal with this as well.

Unfortunatly, the best answer I got was "live with it".

09 September 2003, 11:03 PM
The image exported from the Z buffer probably does not have any AA.

Have you tried X-DOF?

Or you can play with using masks with soft edges in a blur tool. This works great for faking DOF in some shots.

Also there is also a trick to use a grey scale rendered image with LW fog. Somehow you can turn it into a Z buffer image and get a very good DOF in DF.

Robert Zeltsch
09 September 2003, 06:10 PM
Ehm... Can you post an example? I`ve tried to blur the z-depth channel (or create an own) - but the result isn`t satisfyingly...

(I don`t want to buy some new LW-PlugIns for DOF)

09 September 2003, 02:48 AM
Here is a simple example of faking DOF with Fusion.

I used a simple gradient as the depth map but for a 3D scene you can create a grey scale map with fog acting as your depth map. This gives you full AA when doing DOF.

Joel Hooks
09 September 2003, 04:47 PM
one way of making a good z-depth map is to take an omni/point light and set it's attenuation how you want it, link it to the camera, texture everything white, and viola.

I think I picked that up from J Birn's Digital Lighting and Rendering book..

09 September 2003, 05:18 PM
No matter what method or how anti-aliased or no-antialiased your Z-buffer pass is, you will invariably encounter artifacting with DF's Depth Blur node when set to Z space.

This was a response from former Eyeon employee and current DF guru, Jay2k, in response to a similar question I had asked:

"I don't have time to get into great detail here and now, but basicly, what happens in a 2D post blur is that there is no information of the scene behind an object, and thus the blur blurs against the colour information it does have. In this case the object.

What can be done is to seperate your scene into "layers" and blur each one independantly."

Robert Zeltsch
09 September 2003, 04:13 PM
@ alphatron: Jay2K may be right but the problem he describes can be solved with the "Background RGB Buffers". These Buffers should include the color of a pixel behind a pixel in the rendered image. So you can blur against the pixel behind the object edges. You may need a Coverage Buffer (The Z-Coverage Buffer described in the DFX manual) to mark these "Edge-Pixels" in anti aliased images. With all these informations an accurate blur is possible with the Depth Blur Tool.

But the most 3d-apps don`t create this Buffers in the right way!


09 September 2003, 05:02 PM
Exactly Robert, the two 3D programs I use, XSI and Maya, cannot create a Z-coverage channel :(

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