a video signal combiner includes circuitry for generating a gleam key signal for keying a video image which has been spatially transformed , a plurality of multiplier circuits for simultaneously layering multiple key and video signals in parallel , and circuitry for dynamically maintaining or adjusting z data priority as the fill video images are spatially transformed . a gleam key is generated in accordance with dynamic planar description data representing the dynamic planar positioning of the gleam within the resultant video image . the gleam key profile or contrast range can be selectively altered prior to its keying of the video image . the multiple key signals can be selectively prioritized relative to one another . the multiplier circuits share common output compensation circuits . dynamic range for internally generated z video data is maintained at the maximum range possible using normalized z data .