Paths

Paths

Paths(
    positions: Transform | Buffer,
    indices: Transform | Buffer | list | int,
    line_colors: Transform | Buffer | Color,
    line_widths: Transform | Buffer | float,
    line_styles: Transform | Buffer | LineStyle,
    line_joins: Transform | Buffer | LineJoin,
    line_caps: Transform | Buffer | LineCap,
)

Paths is a set of contiguous lines passing through a series of positions (path). Each path can be colored and styled and possess a thickness. Paths always face the viewer such that their apparent thickness is constant. Their end points (caps) can be styled following the SVG specification (butt, round or cap). Their joins can be styled following partially the SVG specification (round, miter or bevel). The number of paths inside a Paths visual is dictated by the indices variables (see below).

Elements

The number of elements (paths) composing a visual is fully specified by the indices and positions parameters. Considering a positions paramters with n position, indices can be:

• int (equal to p)

This indicates paths are composed of p consecutives positions. this require p to be a divider of n. The total number of paths N is equal to n/p.

• Buffer or list of N integers

Each item of the list describes a path made of the given number of consecutive positions. This require the sum of the list to be less or equal to n. The total number of paths is the length of the list N.

• `list of list or Buffer (of integers)

Each item of the list describe a path made of indexed positions. The total number of paths is the length of the list N. When a buffer is used in place of a list, each item must be separated by the value -1 indicating the end of a path.

Example

Paths([a,b,c,d], 2)                # results in two paths: (a,b) and (c,d)
Paths([a,b,c,d], [2,2])            # results in two paths: (a,b) and (c,d)
Paths([a,b,c,d], [[0,1], [2,3]])   # results in two paths: (a,b) and (c,d)
Paths([a,b,c,d], [0,1,-1, 2,3,-1]) # results in two paths: (a,b) and (c,d)

Attributes

Each attribute of the visual can be assigned per visual (all paths), per path, per position or per vertex, depending on the nature of the attribute and the possible limitations of the server. Let's consider a set of n positions that results in P paths producing N vertices.

Attribute	Type	per visual (1)	per path (P)	per positions (n)	per vertex (N)
line_colors	vec4	✓	✓︎︎	✓	✓
line_widths	float	✓	✓︎︎	✓	✓
line_styles	int	✓	✓	-	-
line_joins	int	✓	✓︎︎	-	-
line_caps	ivec2	✓	✓	-	-

Output variables

During rendering, a number of variables are produced and can be referred to in the definition of attributes using the Out transform using their name. The size of these variables are dependents on their nature. Let's consider a set of n positions that results in P paths producing N vertices.

Variable name (string)	Type	Size	Comment
positions/2D	vec2	n	Positions coordinates (screen)
vertex/positions/2D	vec2	N	Path vertex coordinates (screen)
vertex/positions/3D	vec3	N	Path vertex coordinates (space)
vertex/curvilinear/2D	float	N	Curvilinear coordinates along path (2d space)
vertex/curvilinear/3D	float	N	Curvilinear coordinates along path (3d space)

After rendering, once every transforms has been evaluated, a number of variables are readable by other visuals:

Variable name (string)	Type	Size	Comment
vertex/colors	vec4	N	Line color
vertex/widths	float	N	Line width
path/caps	ivec2	P	Line caps
path/joins	int	P	Line joins
path/style	int	P	Line style

python docs/snippets/Paths_init.py

Parameters:

Name	Type	Description	Default
positions	Transform | Buffer	Paths positions (vec3)	required
indices	Transform | List | int	Position indices composing paths (int)	required
line_caps	Transform | Buffer | LineCap	Paths end caps (int)	required
line_colors	Transform | Buffer | Color	Paths line colors (vec4)	required
line_widths	Transform | Buffer | Measure	Paths line width (float)	required

render

render(
    viewport: Viewport,
    model: Matrix = None,
    view: Matrix = None,
    proj: Matrix = None,
)

Render the visual on viewport using the given model, view, proj matrices

Parameters:

Name	Type	Description	Default
viewport	Viewport	Viewport where to render the visual	required
model	Matrix	Model matrix to use for rendering	None
view	Matrix	View matrix to use for rendering	None
proj	Matrix	Projection matrix to use for rendering	None