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The Difference between FPS and Lag

Definitions:

FPS: Frames Per second.

The number of frames of animation which are displayed every second, are called the frame rate. The frame rate is measured in frames per second or fps. The higher the frame rate, the smoother the animation, but the more processing power and system bandwidth is required.

At less than 30 fps, the human eye can single out new images being drawn on the screen. At greater than 72 fps, it is perceived the same as natural vision.

Lag: Latency

Latency is one of the most fundamental issues with communication between devices. It is the transmission delay between sending and receiving of information. The higher the latency, the longer it takes to receive feedback.



Participants in modern internet-controlled, heavily graphics-orientated virtual worlds often confuse fps and lag. When an area cluttered with graphics, and a complex drawing area slows down, all too often people say that the area is laggy, or their Internet connection is not sufficient to handle it. This is patiently untrue, and continued perpetuation of this idea leads people to invest in hardware they don't need, which has no effect on the problem.

A slowdown or sluggishness is to be expected. Data has a long way to travel, in large quantities, so some penalty must be paid. However, is all unresponsiveness in virtual environments really caused by lag?

The majority of lag in social VR worlds occurs via the Internet connection. The Internet architecture was never really designed for real-time interaction, and packets frequently cross thousands or tens of thousands of miles to reach a central server, and come back again - transmission time is always a function of double the distance to server.

It takes time to collect all the data necessary to construct a visual area from the main server - object placement, script commands, sometimes actual object and texture data itself. However, once this is downloaded, it is downloaded. That is to say, once it is on the local computer, it is not going to use the Internet connection again. The job of that equipment is done, and no matter how choppy the experience may be, its no longer anything to do with transmission times.

The task now falls to the graphics hardware. In particular, the graphics accelerator card, if present. If a dedicated graphics card is not present, that's the source of the 'lag' right there. Modern graphical virtual worlds demand dedicated graphical processing power. The graphics hardware has to analyse the data stored in the computer's memory, work out where in the scene each item is - what is occluded behind nearer objects and so does not need to be drawn, what is only partially occluded, and what is fully visible. In more advanced environments, it has to work out shadows, lighting, reflections, organic deforming surfaces, fog levels, or large numbers of complex avatars.

It has to do all this, anywhere from 30 to 80 times each second.

So, the next time you are in a high-density area, cluttered with complex graphics, and things start to slow down. Don't whine and bemoan your Internet connection. It has done its job, consider a better graphics card instead.

Lag and fps. There is a profound difference.

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