1. A computer-implemented method to reduce pipeline stalls during a ray tracing operation involving a fragmented vector, by transferring the fragmented vector into a target register via non-interdependent permute instructions specifying the same operation code (op-code) but different write mask operands, the computer-implemented method comprising: receiving a plurality of permute instructions each containing an op-code field and a plurality of operand fields, the plurality of operand fields including a first operand field comprising a respective source register, a second operand field comprising the target register, and a third operand field comprising a write mask, wherein the plurality of permute instructions specify the same op-code but different write masks, of which each write mask identifies a different word location, of the target register, to write to; transferring the fragmented vector into the target register such that the target register stores the fragmented vector in unfragmented form, via non-interdependent permute instructions specifying the same op-code but different write mask operands, by executing each of the plurality of permute instructions by operation of one or more computer processors, wherein the vector stored in unfragmented form defines an edge of a first of a plurality of interconnected triangles representing at least part of an object in a three-dimensional scene of a virtual environment; and determining whether each of the plurality of interconnected triangles is visible from a viewing perspective, by performing one or more vector operations based on the vector stored in unfragmented form in the target register, whereafter at least a first of the plurality of interconnected triangles, determined to be visible from the viewing perspective, is output.