Volume Rendering Using Dynamic CUDA Warp Marching

A CUDA warp marching method for ray casting volume rendering is proposed to address the problem of low computational resource utilization resulted from warp divergence due to irregular workload for each thread in a warp. We firstly analyzed the reasons for warp divergence in standard CUDA implementation. Warp divergences are eliminated by integrating each single ray with all the threads in a warp, which executes instructions in lock-step. The algorithm of integrating one single ray within one warp is introduced after detailing the mathematical principles and GPU hardware specifications. Dynamic work scheduling strategy is also incorporated into warp marching to further improve the overall performance by better balancing the workloads of streaming multi-processors. Experimental results indicate that our dynamic warp marching method can achieve 1.9-7.9 times speedup as compared with standard CUDA implementation.