WolframLang: Graphics Primitives

Graphics Primitive

• Graphics Primitive is a expression that represents a graphical element, such as line, circle, polygon, text, sphere, tube.
• You use graphics primitive to create graphics, programatically.
• All Plot functions or visualization functions that show graphics, are internally creating a list of graphics primitives, and return it as output.

some graphics primitives are 2D (such as Circle, Disk, Rectangle), some are 3D (e.g. Sphere, Cuboid, Tube), some both (e.g. Point, Line, Polygon).

Example of graphics primitives:

• Point[{45,41}] (2D)
• Point[{44,90,48}] (3D)
• Line[{{331,754}, {557,550}, {888,272}}] (2D)
• Line[{{92,402,927}, {183,643,101}, {229,39,925}}] (3D)

• Polygon[args] (2D or 3D)
• Text[args] (2D)
• Disk[args] (2D)
• Circle[args] (2D)
• Rectangle[args] (2D)
• Sphere[args] (3D)
• Cuboid[args] (3D)
• Tube[args] (3D)

Complete list at SymbolicGraphicsLanguage

Graphics primitives are symbolic. By themselves they do nothing.

Line[{{0, 0}, {2, 1}}]

Graphics primitive usually are bundled together in a list. e.g.

{Line[arg], Line[arg], Polygon[arg], etc}

Displaying Graphics Primitives

To display graphics primitives, put them inside the functions Graphics or Graphics3D.

Example

Graphics Directives

Graphics Directives are things like color, thickness. They control the style and rendering of the graphics primitives.

Here are commonly used graphics directives:

• Red
• Green
• Blue
• Hue
• GrayLevel
• PointSize
• Thickness
• EdgeForm
• FaceForm

• GraphicsDirectives

Graphics directives are used in a list, where they precede the graphics primitives. For example:

How to Extract Graphics from Builtin Plot Functions

Typically, all builtin functions that display graphics return a list such that the first element is a list of graphics primitives (and directives).

so, to exctract them, you can just use First on the result.

(* extract the graphic primitives from a builtin visualization function *)

gr = Plot[ Sin[x], {x,0,5} ];

Length[gr] === 2

Head[gr] === Graphics

(* list of graphics primitives and directives. usually big. *)
First[gr]

Advanced: Discretize Graphics

DiscretizeGraphics and DiscretizeRegion return a MeshRegion. These are critical, when you want to do a transformation on graphics, so that it is applied all points on edge or faces, instead of just on vertexes.