User:Chrisgthorne/sandbox

Introduction
Spatial position jitter, hereafter "spatial jitter", refers to undesirable effects from a spatial resolution related error in applications based on floating point coordinates. Spatial jitter is very significant because it can manifest in a very wide range of applications, e.g.: geospatial, military, games, virtual worlds, and simulation; to name a few. Some jitter examples are: random and unintended motion, rendering errors, physics errors and imprecise interaction. In brief, spatial jitter varies with the resolution of floating point positional values (e.g. coordinates (x,y,z)) and their precision. The resolution of local space around x, y or z, decreases in powers of two with their size: i.e. the distance of this local space from the origin. As resolution decreases, the relative error of coordinates increases, leading to greater error in calculations that use them. The resulting errors cause jitter that is not always noticeable but becomes problematic when it impinges on the quality or accuracy required by an application. Applications that deal with large scales, such as Earth, Solar System or greater, need to take special measures to prevent jitter and maintain the accuracy they need.

Further information
Spatial position jitter is sensitive to spatial resolution and therefore to be distinguished from temporally sensitive Jitter, such as jitter of information/objects due to time lag in networks (this is also called "spatial jitter"). It is for this reason that the term is first introduced as spatial position jitter. For more information on spatial jitter, you may refer to peer-reviewed papers or books providing detailed explanation on this issue and methods to manage or remove it.  Less formal references are also available online.

Mitigation of spatial position jitter
Navigating digital spaces, whether they be virtual worlds, simulations or some abstract representation of data, involves moving the viewpoint relative to the scene/world and rendering the information as seen from the new location. The main approaches to reducing spatial jitter during navigation have in common moving the coordinate origin near where greater accuracy is required (e.g. just prior to calculating, or [rendering]), the next video frame to view). Moving the origin to a viewpoint is mathematically equivalent to moving the entire visible scene, or space, in reverse by the difference between the current view position and the new viewpoint location. This reverse movement is termed the floating origin method. In other words, with floating origin, when the user navigates, the world is moved in reverse by a corresponding amount.  Although floating origin is widely adopted as the general solution to spatial jitter, there are differences in opinion on how to implement it and the performance of different implementations. Approaches described fall into one of the following categories:  There are also different methods for implementing the origin move: An example implementation that needs to be clarified is for the Unity3D game engine. The Unity algorithm that has been persistently referred to over the last decade clearly moves every object at once. The more recent Unity HDRP code documentation is very good but does not specify if it moves every object or if it moves the whole scene each time.
 * 1) Move the origin continuously (in lock-step with navigation input).
 * 2) Move origin after navigating a certain distance.
 * 3) Unclear. Documents unclear or yet to verify if the origin is moved continuouly with navigation or in steps.
 * 1) Move every object in the scene in reverse.
 * 2) Move entire scene in reverse.
 * 3) Unclear. Documents unclear or yet to verify if the entire scene is moved at once or each object is moved.

The field of study and development around mitigating spatial jitter has not yet matured enough where the majority of industry has adopted one of the above alternatives to be the definitive approach. More independent verification with implementations and empirical measurement is required.

Sections and information to be added
Explanatory diagrams and links to more terms already defined in Wikipedia.

Positional Jitter
This section expands the notion of spatial jitter to include other positional variables, such as time.