[Bf-committers] DOF with skewed z-buffer

[Reuben Martin]

On 5/10/06, Ed Halley <ed at halley.cc> wrote:
>
> Reuben Martin wrote:
>  > What would it take to be able to render a z-buffer image, where the z
>  > axis for the buffer was not perpendicular to the image plane?
>
> The lens you're talking about is called a "tilt & shift lens."  You can
> get those for most 35mm camera mounts.  The more general case of the
> situation you're talking about is called a "technical camera," where the
> film plate and the lens are on two independent fixtures, so that you can
> adjust perspective and depth of field and other optical attributes.  The
> two parts are usually cowled with a fabric baffle, the "accordion" that
> you mentioned.

Thanks. I was searching through wikipedia to try to find the correct
technical terms for this. I've never actually used one of these
myself, I just knew it was possible.

>...
>
> In fact, I actually can't think of how the z-buffer would have any
> positive benefit in trying to emulate a different projection or an
> accurate approximation of depth of field anyway.  I'd like to see how, I
> honestly might be missing something, but I doubt it would be faster or
> more effective than simply using a new projection matrix in the first
> place.
>

Well, I'm not thinking about anything that's a spot-on accurate
representation of the real world physics, just an approximation of the
effect. Currently in blender most of the depth-of-field is done in
post by using the zbuffer to determin what parts of the picture get
blurred and how much. It's not technically correct at all, but it's
convincing enough to pass as a depth of field for animation work.

My thinking was that if you could tilt the z axis used in calculating
the zbuffer, the resulting depth of field simulation would have it's
focus plan tilted as well.

-Reuben