Frame Experience Analysis - Tomb Raider

With FCAT on the following pages we will look into Frame Experience Analysis. Basically with the charts shown we are trying to show you graphics anomalies like stutters and glitches in a plotted chart. Lately there has been a new measurement introduced, latency measurements. Basically it is the opposite of FPS.

• FPS mostly measures performance, the number of frames rendered per passing second.
• Frametime aka Frame Experience recordings mostly measures and exposes anomalies - here we look at how long it takes to render one frame. Measure that chronologically and you can see anomalies like peaks and dips in a plotted chart, indicating something could be off. 

We have a detailed article (read here) on the new FCAT methodology used, and it also explains why we do not use FRAPS anymore.

Frametime - Basically the time it takes to render one frame can be monitored and tagged with a number, this is latency. One frame can take say 17ms. Higher latency can indicate a slow framerate, and weird latency spikes indicate a stutter, jitter, twitches basically anomalies that are visible on your monitor.

What Do These Measurements Show?

Basically what these measurements show are anomalies like small glitches, freezes, scene changes and stutters that you can sometimes (and please do read that well, sometimes) see on screen. Below I like to run through a couple of titles with you. Mind you that Average FPS matters more than frametime measurements. It's just an additional page or two of information that from now on we'll be serving you.

Tomb Raider Frame Experience Analysis

Above a percentile chart of the 30 seconds @ 2560x1440. Here we plot FPS and place it in relation to percentiles.

• 50% of the time measured frames is doing 110 FPS. 
• 5% of the frames is at roughly 90 FPS. This is another and valid way of looking at average performance.

Above in red is the Radeon HD 7990 at 2560x1440 using Catalyst 13.8 Beta, in green the GeForce GTX 690 (Geforce driver 320.49 WHQL).

Now this looks a little poor and acatually we started off with the worst title, but please notice that frametime scaling manages to remain roughly below 15 to 20ms,  there are NO VISIBLE STUTTERS. An absolutely smooth experience. With this chart, lower = better. Huge spikes above 40-50ms can be considered a problem or indicate a low framerate (look at the table at the top of this screen).

Now we do see five framedrops, a situation where the GPU for whatever reason decides to not render a frame. 

Our error analysis indeed show these dropped frames, but overall that is just a very consistent experience. So you can't see the dropped frames, but we can measure them. The relevance is close to NIL (unless you'd see hundreds of them), as that could increase the overall framerate. But out of 110 frames per second x 30 seconds = 3300 rendered frames, with five framedrops, it is unusual but not relevant.