In the visual effects industry it is common to shoot a picture of a mirror ball (also known as a light probe) on set, as well as a gray ball for lighting reference.
Ideally, you shoot these at multiple exposures and use a tool to combine them into a single high dynamic range image and/or unwrap the mirrored/gray ball into a spherical environment map.
However, it is often difficult to regain the proper orientation of the spherical map such that it matches the camera used to render the CG scene. Furthermore, a single photo of a mirror/gray ball contains poor data for certain angles that you want to avoid seeing in the final render.
The Mirror Ball and Mirror Ball (mip) shaders are intended to simplify a particular special case where the mirror/gray ball is already shot from the exact camera angle from which the final image will be rendered. These shaders use the mental ray camera coordinate space and apply the mirror/gray ball in this space, hence the orientation of the reflections will always "stick" to the rendering camera.
The Mirror Ball shader does a texture look-up based on the direction of the ray. It will map the proper direction to a point on the mirrored ball and retrieve its color.
| [texture] |
Displays the texture map (connected in the texture parameter port) to be looked up. You can Edit the image clip, or get a New image clip from file or from source. For more information about working with images, see Managing Image Sources & Clips [Data Exchange]. |
| Multiplier |
A multiplier for the texture map. |
| De-Gamma |
If necessary, applies an inverse gamma correction to the texture. If gamma is handled by other shaders in the render tree, or if a global gamma is applied, use a value of 1.0, which means no gamma correction is performed. |
| Blur |
If the texture parameter input points to a literal texture map, then the blur parameter input can be used to blur it. |
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