2D shapes¶

This section presents the main shape classes available in anim.plane, and how to control their geometry and style.

Available shapes¶

The following classes cover the standard 2D shapes.

API class	Demo
`anim.plane.line`	Line
`anim.plane.circle`	Circle
`anim.plane.ellipse`	Ellipse
`anim.plane.rectangle`	Rectangle
`anim.plane.polygon`	Polygon
`anim.plane.path`	Path
`anim.plane.arrow` (composite shape)	Arrow

Anchor point (reference point)¶

Each shape inherits from anim.plane.item and is positioned using a reference point (anchor point). This anchor is the point controlled by anim.plane.item.position (or by anim.plane.item.x and anim.plane.item.y).

The exact geometric meaning of the anchor depends on the shape:

anim.plane.circle: the anchor is the center.
anim.plane.ellipse: the anchor is the center.
anim.plane.line: the anchor is one endpoint by default, or the center if center=True.
anim.plane.rectangle: by default the anchor is the center; with center=[False, False] it becomes the bottom-left corner.
anim.plane.polygon and anim.plane.path: points are defined relative to the anchor.
anim.plane.arrow: the anchor follows the first point of the arrow trajectory.

C.item.rect = anim.plane.rectangle(dimension=[1.2, 0.6], center=[False, False])
C.item.rect.position = [0.0, 0.0]   # bottom-left corner at origin

Rotation and center of rotation¶

Rotations are controlled by anim.plane.item.orientation (in radians), or by calling anim.plane.item.rotate() for relative updates.

The pivot point is controlled by anim.plane.item.center_of_rotation:

for most shapes, default is [0, 0] in local item coordinates
for anim.plane.circle, the natural center rotation is obtained with center_of_rotation=[0, 0]
for polygons/paths, [0, 0] means rotating around the anchor point

import numpy as np

C.item.rect = anim.plane.rectangle(dimension=[1.4, 0.5], position=[0.5, -0.2])

# Absolute orientation (30 degrees)
C.item.rect.orientation = np.pi / 6

# Relative rotation (+15 degrees)
C.item.rect.rotate(np.pi / 12)

# Change pivot to the rectangle corner in local coordinates
C.item.rect.center_of_rotation = [0.7, 0.25]
C.item.rect.orientation = np.pi / 3

Geometry control by shape¶

Each shape exposes specific geometry attributes:

anim.plane.line: Lx, Ly or dimension=[Lx, Ly] define the segment vector.
anim.plane.circle: radius defines size.
anim.plane.ellipse: Lx and Ly (or dimension) define width and height.
anim.plane.rectangle: Lx and Ly (or dimension), plus center for anchor behavior.
anim.plane.polygon: points defines vertices relative to the anchor.
anim.plane.path: points defines a polyline relative to the anchor.
anim.plane.arrow: points defines the trajectory; dedicated options control head and text.

Style: fill and stroke¶

Shape style is controlled by four attributes settable directly on any shape instance, either at construction time or at runtime.

Attribute	Description
`color`	Fill color (string, hex, or `[r, g, b]` in [0, 1]). Set to `None` for no fill (transparent).
`stroke`	Contour color. Set to `None` (default) for no contour.
`thickness`	Contour thickness in scene units (default `0`).
`linestyle`	Contour pattern: `'-'` solid, `'--'` dashed, `':'` dotted, `'-.'` dash-dot.

C.item.ell = anim.plane.ellipse(dimension=[1.2, 0.5], position=[0.0, 0.0])

# Fill only
C.item.ell.color = '#4aa3ff'

# Fill + contour
C.item.ell.color = '#4aa3ff'
C.item.ell.stroke = 'white'
C.item.ell.thickness = 0.01

# Contour only (no fill)
C.item.ell.color = None
C.item.ell.stroke = 'white'
C.item.ell.thickness = 0.01
C.item.ell.linestyle = '--'

For anim.plane.line and anim.plane.path, there is no fill — only stroke, thickness, and linestyle apply.