Chief Blur Buster wrote:Conclusion/TLDR:
- Scanning creates tilt effect on motion perpendicular to scan direction;
- CRTs and non-strobed LCD will have the scan tilting effect;
- Higher refresh rates / faster scanning will have less tilting effect;
- LightBoost (and similar strobe backlights) will not have the scan tilting effect;
- Multiscanning will create stationary tear-line artifacts;
- Interlacing will create venetian blind artifacts;
- Anything other than all-at-once presentation can cause motion distortions, in one form or another;
- Sequential scanning is the least-distorting method of scanning, short of doing all-at-once presentation.
What you forgot to mention is input lag variation - input lag at the top of the screen will be lower then at the bottom.
Of course you could race the beam (rendering each scanline seperately) or use continuous predictive time warp with eye-tracking, but these come with big drawbacks.
As input lag variation (not total lag) and visual instability cause nausea among other issues, it is preferable to do away with raster-scan altogether and use simultaneous refresh- what Valve called 'global display', using their custom made display drivers for their latest VR prototype.
Side note: To do this, you need to need to pre-buffer the image, but at maximum scanout speed with variable v-blank (think g-sync), lateny can be reduced to non-problematic levels.
Our prototype uses global display, where all pixelsare illuminated simultaneously. This avoids the
compression, stretching, and tilting problems that can occur with the more standard rolling display,
where pixels are illuminated in a scanned sequence over the course of a frame. It may be that the
artifacts of rolling display can be largely corrected by adjusting the frame buffer during each frame to
account for eye motion, but that’s not yet proven; also, while head motion can often be used as a
proxy for eye motion, without eye tracking there will always be failure cases, and low-latency headmounted eye tracking is not a solved problem. So right now global display is the only approach known
http://blogs.valvesoftware.com/abrash/l ... ar-and-vr/
http://blogs.valvesoftware.com/abrash/r ... s-the-eye/
http://www.altdevblogaday.com/2013/02/2 ... trategies/
http://media.steampowered.com/apps/abra ... 202014.pdf