RTRT Spectre

A computer game inspired by Spectre VR, but updated with a realtime raytracing rendering engine.

Only a few basic optimizations have been implemented. The rendering is done entirely on the CPU, no GPU assistance is used whatsoever, but it is multithreaded. Objects have bounding boxes, and those bounding boxes are projected into screen space to optimize primary ray tests. In addition, “skip tracing” provides a substantial speed boost with little quality loss…every other pixel on every other line, or every third pixel on every third line is rendered, and the intervening pixels are simply interpolated if the raytraced pixels are similar enough. The result is that less time is spent rendering smooth expanses of color, while edges do not get as blocky as they are if pixel doubling or tripling is used.

Skip-1 or skip-2 tracing and pixel doubling or tripling may be combined, giving a variety of lower quality render modes. The highest quality skip tracing mode is difficult to distinguish from full quality, low quality skip tracing loses detail on small objects and causes some odd edge artifacts. With skip tracing, a 2 GHz Intel Core Duo iMac can render at a marginally playable framerate, and an 8-core 2.8 GHz Xeon Mac Pro can manage quite well.

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