A ray-tracing system configured to perform intersection testing, comprising: a tester module for testing rays for intersection with a volume, the tester module being configured to receive a packet of one or more rays to be tested for intersection with the volume, wherein the tester module comprises: a first set of one or more testers configured to perform intersection testing at a first level of precision to provide intersection testing results, wherein for a first type of the intersection testing result from the first set of one or more testers intersection testing does not need to be reperformed at a second level of precision greater than the first level of precision, and for a second type of the intersection testing result from the first set of one or more testers intersection testing is to be reperformed at the second level of precision; and a second set of one or more testers configured to perform intersection testing at the second level of precision; wherein the tester module is configured to: allocate a ray from a received packet to one of the first set of testers for intersection testing at the first level of precision; identify the type of an intersection testing result for the ray provided by said one of the first set of testers to determine whether intersection testing for the ray is to be reperformed at the second level of precision; and if it is determined that intersection testing for the ray is to be reperformed at the second level of precision, allocate the ray to one of the second set of testers for intersection testing at the second level of precision.
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