Editing Real-time computer graphics (section)

=== Geometry stage ===
{{Main|Polygonal modeling}}
The geometry stage manipulates polygons and vertices to compute what to draw, how to draw it and where to draw it. Usually, these operations are performed by specialized hardware or GPUs.<ref name="frpi">{{cite book|url={{google books |plainurl=y |id=W4bSBQAAQBA|page=5}}|title=Computer Graphics: From Pixels to Programmable Graphics Hardware|last=Boresko|first=Alexey|author2=Evgeniy Shikin|publisher=CRC Press|year=2013|isbn=9781482215571|page=5|access-date=22 September 2017}}{{dead link|date=September 2019}}</ref> Variations across graphics hardware mean that the "geometry stage" may actually be implemented as several consecutive stages.

==== Model and view transformation ====
Before the final model is shown on the output device, the model is transformed onto multiple spaces or [[coordinate system]]s. Transformations move and manipulate objects by altering their vertices. ''Transformation'' is the general term for the four specific ways that manipulate the shape or position of a point, line or shape.

==== Lighting ====
In order to give the model a more realistic appearance, one or more light sources are usually established during transformation. However, this stage cannot be reached without first transforming the 3D scene into view space. In view space, the observer (camera) is typically placed at the origin. If using a [[Cartesian coordinate system#Orientation and handedness|right-handed]] coordinate system (which is considered standard), the observer looks in the direction of the negative z-axis with the y-axis pointing upwards and the x-axis pointing to the right.

==== Projection ====
{{Main|Graphical projection}}
Projection is a transformation used to represent a 3D model in a 2D space. The two main types of projection are [[orthographic projection]] (also called parallel) and [[Perspective (graphical)|perspective projection]]. The main characteristic of an orthographic projection is that parallel lines remain parallel after the transformation. Perspective projection utilizes the concept that if the distance between the observer and model increases, the model appears smaller than before. Essentially, perspective projection mimics human sight.

==== Clipping ====
[[Clipping (computer graphics)|Clipping]] is the process of removing primitives that are outside of the view box in order to facilitate the rasterizer stage. Once those primitives are removed, the primitives that remain will be drawn into new triangles that reach the next stage.

==== Screen mapping ====
The purpose of screen mapping is to find out the coordinates of the primitives during the clipping stage.

==== Rasterizer stage ====
The rasterizer stage applies color and turns the graphic elements into pixels or picture elements.