czm_viewerPositionWC
An automatic GLSL uniform representing the position of the viewer (camera) in world coordinates.
Like all automatic uniforms, czm_sunDirectionWC does not need to be explicitly declared.
However, it can be explicitly declared when a shader is also used by other applications such
as a third-party authoring tool.
Example
// GLSL declaration uniform vec3 czm_viewerPositionWC;