This shader is intended
as an environment shader (apply as an Environment Map), because
it looks up based on the ray direction. It maps the proper direction
to a point on the chrome ball and retrieves its color.
In the visual effects
industry it is common practice to photograph a chrome ball (also
known as a “light probe”) on set, as well as a
gray ball for
Ideally, one shoots these
at multiple exposures and uses software such as Photosphere (Macintosh)
or HDRShop (PC) to combine them into a single high-dynamic-range
image and/or unwrap the chrome/gray ball into a spherical environment
However, it is often
difficult to regain the proper orientation of spherical map so it
matches the camera used to render the CG scene. Furthermore, a single
photo of a chrome/gray ball contains poor data for certain angles
that one might want to avoid seeing in the final render.
These shaders are intended
to simplify a special case: When the chrome/gray ball is already
shot from the exact camera angle from which the final image is to
It simply utilizes the
mental ray camera coordinate space and applies the chrome/gray ball
in this space, hence the orientation of the reflections will always
“stick” to the rendering camera.
For additional information
and illustrations, see Help menu Additional Help mr Production Shader Library Chapter 6: Mirror/Gray
- Chrome/Mirror Ball Image
Click the Browse button to
specify the file containing the chrome ball image. The image should
be cropped so the ball exactly touches the edges of the image. Alternatively,
click the map button to specify a procedural map.
A multiplier for the chrome
- Reverse Gamma Correction
Applies an inverse gamma
correction to the texture.
- Blur (literal mental ray image files only)
Blur the image. This applies
only to literal mental ray textures; that is, bitmap images specified
with the Browse button, rather than maps specified with the map button.