Compositing paint effects
Hey guys! In the past I've had good luck with getting help around here so I'll throw another one at you. 
I have a scene that uses a rather large scale. I generally try to keep my scale small at all times to avoid this problem, but alas... I had some stuff that I imported from CAD and this is the scale they used.
So the render looks very bad in Software Render. Stuff is poking through other stuff even though it's as much as a full unit apart, etc.
That said, Mental Ray seems a better choice because it doesn't have this problem regardless of my scale. (within reason) but it doesn't support paint effects. I use paint effects for plants in my scene.
Software Render can render the paint effects separately, and I can composite it later. Sounds nice, but when the "only render paint effects" option is on, it renders... nothing. It does load the depth file (required for "paint effects only" renders) but it displays this file and doesn't render over it.
I refered to the manual first...
To create a composite
Render the scene or animation without Paint Effects strokes as follows:
1. Select Window > Rendering Editors > Render Globals.
Got it.
If you are compositing an animation, beside Frame/Animation Ext, select name.#.ext.
Not an animation, so skip that.
In the Image File Output section, turn on Depth Channel (Z Depth) beside Channels.
*click* got it.
In the Paint Effects Rendering Options section, turn off Enable Stroke Rendering.
got it...
Render the scene or animation (for example, rainyday). For details, see the online Rendering guide.
Okay, I did this. The rendered image doesn't look any diffrent, except I don't see the paint effects. Makes sense, since I told it not to render the paint effects.
Save the scene using a different file name to ensure that the rendered images do not overwrite each other (for example, rainydaywithstrokes).
Saved, and copied the path to the clipboard.
Render the strokes with the scene as follows:
Make sure the camera and the lights are set up to match the camera and lights in step #1.
Nothing's changed.
If you are compositing an animation, beside Frame/Animation Ext, select name.#.ext.
Again, not an animation...
In the Paint Effects Rendering Options section, turn on Enable Stroke Rendering and Only Render Strokes.
Did this.
Beside Read This Depth File, type the location and name of the depth file for the image you rendered in step #1. Make sure it is an absolute path name (for example, /h/pearce/rainyday.iff or c:\pearce\rainyday.iff).
Yup, copied the path from the clipboard. The guide goes on to provide some additional information for animating.
So when I render, it pulls up the depth map (which looks like any other image, full color even) but I see no paint effects.
I'm wondering if it has something to do with the depth map (Perhaps the paint effects are not where they should be? Is it supposed to be full color like that, or something black and white?)
Anyway, thanks in advance for your help. Sorry about the longer-than-necessary post. 
Me and THIS army!