Back in about 2000 I remember exchanging emails with a guy who had built a modified renderer for (I think) the Half-Life 1 engine. He was using audio rendering

Back in about 2000 I remember exchanging emails with a guy who had built a modified renderer for (I think) the Half-Life 1 engine. He was using audio rendering to enable blind players to play first person shooters. My recollection is he was using a series of horizontal scan lines across the display region with different octaves or similar indicating which scan line was being "rendered" and different tones indicating the brightness value along the sweep of each scan line. I think he was primarily using mono audio at the time, but it's been long enough that I can't entirely recall.