This paper presents algorithms for object-space parallel polygon rendering on hypercube-connected multicomputers. A modified scanline z-buffer algorithm is proposed for local rendering phase. The proposed algorithm avoids message fragmentation by packing local foremost pixels in consecutive memory locations efficiently, and it eliminates the initialization of scanline z-buffer for each scanline. Several algorithms, utilizing different communication strategies and topological embeddings, are proposed for global z-buffering of local foremost pixels during the pixel merging phase. The performance comparison of these pixel merging algorithms are presented based on the communication overhead incurred in each scheme. Two adaptive screen subdivision heuristics are proposed for load balancing in the pixel merging phase. These heuristics utilize the distribution of foremost pixels on the screen for the subdivision. Experimental results obtained on an Intel's iPSC/2 hypercube multicomputer and a Parsytec CC system are presented. Rendering rates of 300K--700K triangles per second are attained on 16 processors of Parsytec CC system in the rendering of datasets from publicly available SPD database.