buffer expert?

[illusory]

Does anyone know how to control the range of depth in an alpha image, exported from the buffer?

A couple pics will no doubt explain this best.

The first depth-alpha image below was made with no background. The second image, was made with a background hemisphere fairly close.
So , the depth of the overall field behind the subject obviously affects things.
The first image, which has a more gradual transition from light to dark than the second image, is closer to what I need.

What I need is an even more gradual transition than the first pic has.
But obviously I can't go past infinity in my depth of field!

Is there another way to affect how quickly things go from dark to light?

BTW, i inverted the dark/light in these images, in photoshop, for clarity, FYI.

thanks for any knowledge anyone cares to share,
NJ

[illusory]

the second image

[Neil_Campbell]

As you've already discovered, the depth buffer tries to be smart and get the whole scene in on the picture, so the black to white gradient is stretched across the whole range of depths - but that takes control away from the user in situations like yours.

There's a couple of ways of sorting out your depth map:

- import the current depth buffer into Photoshop and play with Levels or Curves to get the effect you're looking for

- put another object in the scene behind the human figure, and move it closer / further away from the camera to alter the contrast across the figure (basically by forcing LW to stretch the depth map across two objects, one of which you can reposition to alter the degree of stretching of the depth map)

- ignore depth map altogether - take a copy of your scene and objects, delete all textures and remove all lights, make sure the camera is facing along the x or z axis, put a null in the same location as the camera, then put a gradient on the luminosity channel of the human figure keyed off x (or z) distance to null, and play with the gradient min / max settings to alter the contrast

HTH

[Red_Oddity]

Or, just use a white Linear Fog and set all objects to matte objects (found under the Render Tab of the Object Property panel)

[illusory]

Excellent ideas, I'll try them out.

Thanks!!
NJ