Hit group (used by [RenderingDevice]). Defines a hit group for use with [method RenderingDevice.raytracing_pipeline_create]. A hit group combines shaders that are executed when a ray intersects geometry. It may include a closest-hit shader, any-hit shader, and intersection shader. Hit groups are referenced by index when populating hit shader binding tables using [method RenderingDevice.hit_sbt_range_update]. Any-hit shader for this hit group. Executed for each potential intersection. Can be [code]null[/code]. Closest-hit shader for this hit group. Executed for the closest intersection. Can be [code]null[/code]. Intersection shader for this hit group. Required for non-triangle geometry. Must be [code]null[/code] when using for triangle geometry.