8

90 Chapter 17: Rendering
To render depth-of-field effects with mental ray,
ray tracing (the Ray Trace toggle) must be enabled
on the Render Scene dialog > Renderer panel >
Rendering Algorithms rollout (page 3–113) .You
must also enable depth of field for the camera:
in the camera’s Multi-Pass Effect g roup, choose
“Depth Of Field (mental ray)” as the depth-of-field
type. (If you choose the scanline renderer’s Depth
Of Field option, the rendering that results can be
out of focus.)
The mental ray renderer uses the camera’s target
distance and f-Stop parameters to control the
depth-of-field effect.
The camera’s target distance determines the focus
plane. The focus plane is the distance from the
camera at which the scene is completely in focus.
Focus plane in relation to a cam era
Here it is set to the middle apple, as in the prev ious
renderings.
Focus plane in relation to a cam era
Here it is set to the nearest apple, as in the renderings that
follow.
The f-stop controls the amount of blurring at
distances other than the focus plane distance. In
a real-world camera, the f-stop measures the size
of the lens’s aperture. The lower the f-stop value,
the larger the aperture and the narrower the depth
of field. So increasing the f-stop value broadens
the depth of field, and decreasing the f-stop value
narrows the depth of field.