It is known as a circumference to the closed line of curved format and flat appearance in which the points are equidistant from the central point that is located in the same plane. This distance that separates the set of points and the central area is known as the radius, while the line segment that makes up a pair of aligned radii is called the diameter.

The diameter, as has been determined, is the largest distance that can be established between two points that belong to the same circumference. The length of this diameter, on the other hand, is twice the length of the radius.

Other elements that can be recognized when examining a circumference are the arc (such as the curved segment of points that makes up every circumference), the chord (that is, the segment that guarantees the union of two points), the tangent line (which makes contact at a single point) and the secant line (which makes contact at a pair of points).

In relation to the relative positions of the points with respect to the circumference, it must be said that a point can be interior (with respect to which the distance from the central zone to the point is smaller than the measure of the length of the radius), belonging to (where the extent that separates the center of the point coincides with the length of the radius) or exterior (where the separation between the center and the point exceeds the length of the radius).

Although in everyday language they are usually used as synonyms, it should be noted that circumference and circle do not mean the same thing. The circle, says the theory, is the geometric space based on the points that are part of a circle: this means that the circumference constitutes the perimeter of a circle.

According to DigoPaul, the notion of circumference, therefore, is also used to name the contour of a certain surface, area or terrain. For example: *“The fencing allows the animals to be kept within the circumference of our property*. *“*

### Use of Circles in Graphical Programming

In video games, as well as in other types of interactive graphic applications, it is necessary to indicate to the processor what is the limit of the objects that are observed on the screen, to prevent them from overlapping. A clear example is a character who runs through a labyrinth and, when walking against a wall, cannot cross it. For people who do not have any technical knowledge related to this topic, it can be difficult to understand that the program does not know that “a wall is solid and you cannot pass through it.” But it is necessary to remember that, as they say in everyday speech, for a computer everything is “ones and zeros”; that is, they do not understand the characteristics of bodies, or concepts of physics or mathematics. It simply reproduces as a slave everything that is indicated.

To prevent an object from going through a wall, for example, so – called collision systems are created, although their name may vary depending on the developer and the language. Basically, it is a series of conventions and functions that establish how many types of interaction exist within the game universe and what consequences each case has. When implemented, what was once a series of graphics without properties becomes a world that can be explored by walking, jumping, climbing, swimming, climbing stairs, and passing through narrow tunnels.

Traditionally, the most commonly used collision types in video games are squares and circumferences, each with characteristics and different purposes. It is worth mentioning that they do not necessarily represent an object or being in a similar way, but the decision to choose one or the other depends more on the type of interaction that this element will have with the environment. If you want to delimit the body of a character such as Super Mario in a game in which the action takes place in 2 dimensions (the camera moves sideways and not “to and from the screen”), probably the most appropriate option It is a rectangle, the longest sides of which will represent the height of the famous plumber, while the remaining two will represent both its width and depth, since it is a flat image.

At first glance, a human being does not have the shape of a rectangle, and depending on the degree of complexity, it is possible to use as many figures as desired to represent its limits. A circumference could well be used for your head and hands, and rectangles for the rest of your body parts. The advantage of the circumference is that it allows very precise calculations of possible collisions coming from all directions without demanding much work from the processor and always performing the same check: if the distance between a certain point of an external object and the center of the circumference is equal or less than the radius, then they are making contact.