Acceleration structure instance (used by [RenderingDevice]). [RDAccelerationStructureInstance] describes an instance of a Bottom-Level Acceleration Structure (BLAS) used in the [method RenderingDevice.tlas_build] method. The BLAS referenced by this instance. If [code]null[/code], the instance is treated as a placeholder but still contributes to [code]gl_InstanceIndex[/code] in GLSL. Flags for the instance. Hit shader binding table range used for this instance, allocated using the [method RenderingDevice.hit_sbt_range_alloc] method. Custom instance ID that can be accessed in GLSL using [code]gl_InstanceCustomIndexEXT[/code]. Visibility mask used to control which rays can intersect this instance. Transform applied to the referenced BLAS for this instance.