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Vertex Instructions

This module includes all the classes for drawing simple vertex objects.

Updating properties

The list attributes of the graphics instruction classes (e.g. Triangle.points, Mesh.indices etc.) are not Kivy properties but Python properties. As a consequence, the graphics will only be updated when the list object itself is changed and not when list values are modified.

For example in python:

class MyWidget(Button):

    triangle = ObjectProperty(None)
    def __init__(self, **kwargs):
        super(MyWidget, self).__init__(**kwargs)
        with self.canvas:
            self.triangle = Triangle(points=[0,0, 100,100, 200,0])

and in kv:

<MyWidget>:
    text: 'Update'
    on_press:
        self.triangle.points[3] = 400

Although pressing the button will change the triangle coordinates, the graphics will not be updated because the list itself has not changed. Similarly, no updates will occur using any syntax that changes only elements of the list e.g. self.triangle.points[0:2] = [10,10] or self.triangle.points.insert(10) etc. To force an update after a change, the list variable itself must be changed, which in this case can be achieved with:

<MyWidget>:
    text: 'Update'
    on_press:
        self.triangle.points[3] = 400
        self.triangle.points = self.triangle.points
class kivy.graphics.vertex_instructions.Triangle

Bases: kivy.graphics.instructions.VertexInstruction

A 2d triangle.

Parameters:
points: list

List of points in the format (x1, y1, x2, y2, x3, y3).

points

Property for getting/settings points of the triangle.

class kivy.graphics.vertex_instructions.Quad

Bases: kivy.graphics.instructions.VertexInstruction

A 2d quad.

Parameters:
points: list

List of point in the format (x1, y1, x2, y2, x3, y3, x4, y4).

points

Property for getting/settings points of the quad.

class kivy.graphics.vertex_instructions.Rectangle

Bases: kivy.graphics.instructions.VertexInstruction

A 2d rectangle.

Parameters:
pos: list

Position of the rectangle, in the format (x, y).

size: list

Size of the rectangle, in the format (width, height).

pos

Property for getting/settings the position of the rectangle.

size

Property for getting/settings the size of the rectangle.

class kivy.graphics.vertex_instructions.RoundedRectangle

Bases: kivy.graphics.vertex_instructions.Rectangle

A 2D rounded rectangle.

New in version 1.9.1.

Parameters:
segments: int, defaults to 10

Define how many segments are needed for drawing the rounded corner. The drawing will be smoother if you have many segments.

radius: list, defaults to [(10.0, 10.0), (10.0, 10.0), (10.0, 10.0), (10.0, 10.0)]

Specifies the radii used for the rounded corners clockwise: top-left, top-right, bottom-right, bottom-left. Elements of the list can be numbers or tuples of two numbers to specify different x,y dimensions. One value will define all corner radii to be of this value. Four values will define each corner radius separately. Higher numbers of values will be truncated to four. The first value will be used for all corners if there are fewer than four values.

radius

Corner radii of the rounded rectangle, defaults to [10,].

segments

Property for getting/setting the number of segments for each corner.

class kivy.graphics.vertex_instructions.BorderImage

Bases: kivy.graphics.vertex_instructions.Rectangle

A 2d border image. The behavior of the border image is similar to the concept of a CSS3 border-image.

Parameters:
border: list

Border information in the format (bottom, right, top, left). Each value is in pixels.

auto_scale: string

New in version 1.9.1.

Changed in version 1.9.2: This used to be a bool and has been changed to be a string state.

Can be one of ‘off’, ‘both’, ‘x_only’, ‘y_only’, ‘y_full_x_lower’, ‘x_full_y_lower’, ‘both_lower’.

Autoscale controls the behavior of the 9-slice.

By default the border values are preserved exactly, meaning that if the total size of the object is smaller than the border values you will have some ‘rendering errors’ where your texture appears inside out. This also makes it impossible to achieve a rounded button that scales larger than the size of its source texture. The various options for auto_scale will let you achieve some mixes of the 2 types of rendering.

‘off’: is the default and behaves as BorderImage did when auto_scale was False before.

‘both’: Scales both x and y dimension borders according to the size of the BorderImage, this disables the BorderImage making it render the same as a regular Image.

‘x_only’: The Y dimension functions as the default, and the X scales to the size of the BorderImage’s width.

‘y_only’: The X dimension functions as the default, and the Y scales to the size of the BorderImage’s height.

‘y_full_x_lower’: Y scales as in ‘y_only’, Y scales if the size of the scaled version would be smaller than the provided border only.

‘x_full_y_lower’: X scales as in ‘x_only’, Y scales if the size of the scaled version would be smaller than the provided border only.

‘both_lower’: This is what auto_scale did when it was True in 1.9.1 Both X and Y dimensions will be scaled if the BorderImage is smaller than the source.

If the BorderImage’s size is less than the sum of it’s borders, horizontally or vertically, and this property is set to True, the borders will be rescaled to accommodate for the smaller size.

auto_scale

Property for setting if the corners are automatically scaled when the BorderImage is too small.

border

Property for getting/setting the border of the class.

display_border

Property for getting/setting the border display size.

class kivy.graphics.vertex_instructions.Ellipse

Bases: kivy.graphics.vertex_instructions.Rectangle

A 2D ellipse.

Changed in version 1.0.7: Added angle_start and angle_end.

Parameters:
segments: int, defaults to 180

Define how many segments are needed for drawing the ellipse. The drawing will be smoother if you have many segments.

angle_start: int, defaults to 0

Specifies the starting angle, in degrees, of the disk portion.

angle_end: int, defaults to 360

Specifies the ending angle, in degrees, of the disk portion.

angle_end

End angle of the ellipse in degrees, defaults to 360.

angle_start

Start angle of the ellipse in degrees, defaults to 0.

segments

Property for getting/setting the number of segments of the ellipse.

class kivy.graphics.vertex_instructions.Line

Bases: kivy.graphics.instructions.VertexInstruction

A 2d line.

Drawing a line can be done easily:

with self.canvas:
    Line(points=[100, 100, 200, 100, 100, 200], width=10)

The line has 3 internal drawing modes that you should be aware of for optimal results:

  1. If the width is 1.0, then the standard GL_LINE drawing from OpenGL will be used. dash_length and dash_offset will work, while properties for cap and joint have no meaning here.
  2. If the width is greater than 1.0, then a custom drawing method, based on triangulation, will be used. dash_length and dash_offset do not work in this mode. Additionally, if the current color has an alpha less than 1.0, a stencil will be used internally to draw the line.
_images/line-instruction.png
Parameters:
points: list

List of points in the format (x1, y1, x2, y2…)

dash_length: int

Length of a segment (if dashed), defaults to 1.

dash_offset: int

Offset between the end of a segment and the beginning of the next one, defaults to 0. Changing this makes it dashed.

width: float

Width of the line, defaults to 1.0.

cap: str, defaults to ‘round’

See cap for more information.

joint: str, defaults to ‘round’

See joint for more information.

cap_precision: int, defaults to 10

See cap_precision for more information

joint_precision: int, defaults to 10

See joint_precision for more information See cap_precision for more information.

joint_precision: int, defaults to 10

See joint_precision for more information.

close: bool, defaults to False

If True, the line will be closed.

circle: list

If set, the points will be set to build a circle. See circle for more information.

ellipse: list

If set, the points will be set to build an ellipse. See ellipse for more information.

rectangle: list

If set, the points will be set to build a rectangle. See rectangle for more information.

bezier: list

If set, the points will be set to build a bezier line. See bezier for more information.

bezier_precision: int, defaults to 180

Precision of the Bezier drawing.

Changed in version 1.0.8: dash_offset and dash_length have been added.

Changed in version 1.4.1: width, cap, joint, cap_precision, joint_precision, close, ellipse, rectangle have been added.

Changed in version 1.4.1: bezier, bezier_precision have been added.

bezier

Use this property to build a bezier line, without calculating the points. You can only set this property, not get it.

The argument must be a tuple of 2n elements, n being the number of points.

Usage:

Line(bezier=(x1, y1, x2, y2, x3, y3)

New in version 1.4.2.

Note

Bezier lines calculations are inexpensive for a low number of points, but complexity is quadratic, so lines with a lot of points can be very expensive to build, use with care!

bezier_precision

Number of iteration for drawing the bezier between 2 segments, defaults to 180. The bezier_precision must be at least 1.

New in version 1.4.2.

cap

Determine the cap of the line, defaults to ‘round’. Can be one of ‘none’, ‘square’ or ‘round’

New in version 1.4.1.

cap_precision

Number of iteration for drawing the “round” cap, defaults to 10. The cap_precision must be at least 1.

New in version 1.4.1.

circle

Use this property to build a circle, without calculating the points. You can only set this property, not get it.

The argument must be a tuple of (center_x, center_y, radius, angle_start, angle_end, segments):

  • center_x and center_y represent the center of the circle
  • radius represent the radius of the circle
  • (optional) angle_start and angle_end are in degree. The default value is 0 and 360.
  • (optional) segments is the precision of the ellipse. The default value is calculated from the range between angle.

Note that it’s up to you to close the circle or not.

For example, for building a simple ellipse, in python:

# simple circle
Line(circle=(150, 150, 50))

# only from 90 to 180 degrees
Line(circle=(150, 150, 50, 90, 180))

# only from 90 to 180 degrees, with few segments
Line(circle=(150, 150, 50, 90, 180, 20))

New in version 1.4.1.

close

If True, the line will be closed.

New in version 1.4.1.

dash_length

Property for getting/setting the length of the dashes in the curve

New in version 1.0.8.

dash_offset

Property for getting/setting the offset between the dashes in the curve

New in version 1.0.8.

ellipse

Use this property to build an ellipse, without calculating the points. You can only set this property, not get it.

The argument must be a tuple of (x, y, width, height, angle_start, angle_end, segments):

  • x and y represent the bottom left of the ellipse
  • width and height represent the size of the ellipse
  • (optional) angle_start and angle_end are in degree. The default value is 0 and 360.
  • (optional) segments is the precision of the ellipse. The default value is calculated from the range between angle.

Note that it’s up to you to close the ellipse or not.

For example, for building a simple ellipse, in python:

# simple ellipse
Line(ellipse=(0, 0, 150, 150))

# only from 90 to 180 degrees
Line(ellipse=(0, 0, 150, 150, 90, 180))

# only from 90 to 180 degrees, with few segments
Line(ellipse=(0, 0, 150, 150, 90, 180, 20))

New in version 1.4.1.

joint

Determine the join of the line, defaults to ‘round’. Can be one of ‘none’, ‘round’, ‘bevel’, ‘miter’.

New in version 1.4.1.

joint_precision

Number of iteration for drawing the “round” joint, defaults to 10. The joint_precision must be at least 1.

New in version 1.4.1.

points

Property for getting/settings points of the line

Warning

This will always reconstruct the whole graphics from the new points list. It can be very CPU expensive.

rectangle

Use this property to build a rectangle, without calculating the points. You can only set this property, not get it.

The argument must be a tuple of (x, y, width, height):

  • x and y represent the bottom-left position of the rectangle
  • width and height represent the size

The line is automatically closed.

Usage:

Line(rectangle=(0, 0, 200, 200))

New in version 1.4.1.

rounded_rectangle

Use this property to build a rectangle, without calculating the points. You can only set this property, not get it.

The argument must be a tuple of one of the following forms:

  • (x, y, width, height, corner_radius)
  • (x, y, width, height, corner_radius, resolution)
  • (x, y, width, height, corner_radius1, corner_radius2, corner_radius3, corner_radius4)
  • (x, y, width, height, corner_radius1, corner_radius2, corner_radius3, corner_radius4, resolution)
  • x and y represent the bottom-left position of the rectangle
  • width and height represent the size
  • corner_radius is the number of pixels between two borders and the center of the circle arc joining them
  • resolution is the number of line segment that will be used to draw the circle arc at each corner (defaults to 30)

The line is automatically closed.

Usage:

Line(rounded_rectangle=(0, 0, 200, 200, 10, 20, 30, 40, 100))

New in version 1.9.0.

width

Determine the width of the line, defaults to 1.0.

New in version 1.4.1.

class kivy.graphics.vertex_instructions.Point

Bases: kivy.graphics.instructions.VertexInstruction

A list of 2d points. Each point is represented as a square with a width/height of 2 times the pointsize.

Parameters:
points: list

List of points in the format (x1, y1, x2, y2…), where each pair of coordinates specifies the center of a new point.

pointsize: float, defaults to 1.

The size of the point, measured from the center to the edge. A value of 1.0 therefore means the real size will be 2.0 x 2.0.

Warning

Starting from version 1.0.7, vertex instruction have a limit of 65535 vertices (indices of vertex to be accurate). 2 entries in the list (x, y) will be converted to 4 vertices. So the limit inside Point() class is 2^15-2.

add_point()

Add a point to the current points list.

If you intend to add multiple points, prefer to use this method instead of reassigning a new points list. Assigning a new points list will recalculate and reupload the whole buffer into the GPU. If you use add_point, it will only upload the changes.

points

Property for getting/settings the center points in the points list. Each pair of coordinates specifies the center of a new point.

pointsize

Property for getting/setting point size. The size is measured from the center to the edge, so a value of 1.0 means the real size will be 2.0 x 2.0.

class kivy.graphics.vertex_instructions.Mesh

Bases: kivy.graphics.instructions.VertexInstruction

A 2d mesh.

In OpenGL ES 2.0 and in our graphics implementation, you cannot have more than 65535 indices.

A list of vertices is described as:

vertices = [x1, y1, u1, v1, x2, y2, u2, v2, ...]
            |            |  |            |
            +---- i1 ----+  +---- i2 ----+

If you want to draw a triangle, add 3 vertices. You can then make an indices list as follows:

indices = [0, 1, 2]

New in version 1.1.0.

Parameters:
vertices: iterable

List of vertices in the format (x1, y1, u1, v1, x2, y2, u2, v2…).

indices: iterable

List of indices in the format (i1, i2, i3…).

mode: str

Mode of the vbo. Check mode for more information. Defaults to ‘points’.

fmt: list

The format for vertices, by default, each vertex is described by 2D coordinates (x, y) and 2D texture coordinate (u, v). Each element of the list should be a tuple or list, of the form

(variable_name, size, type)

which will allow mapping vertex data to the glsl instructions.

[(b’v_pos’, 2, ‘float’), (b’v_tc’, 2, ‘float’),]

will allow using

attribute vec2 v_pos; attribute vec2 v_tc;

in glsl’s vertex shader.

Changed in version 1.8.1: Before, vertices and indices would always be converted to a list, now, they are only converted to a list if they do not implement the buffer interface. So e.g. numpy arrays, python arrays etc. are used in place, without creating any additional copies. However, the buffers cannot be readonly (even though they are not changed, due to a cython limitation) and must be contiguous in memory.

Note

When passing a memoryview or a instance that implements the buffer interface, vertices should be a buffer of floats (‘f’ code in python array) and indices should be a buffer of unsigned short (‘H’ code in python array). Arrays in other formats will still have to be converted internally, negating any potential gain.

indices

Vertex indices used to specify the order when drawing the mesh.

mode

VBO Mode used for drawing vertices/indices. Can be one of ‘points’, ‘line_strip’, ‘line_loop’, ‘lines’, ‘triangles’, ‘triangle_strip’ or ‘triangle_fan’.

vertices

List of x, y, u, v coordinates used to construct the Mesh. Right now, the Mesh instruction doesn’t allow you to change the format of the vertices, which means it’s only x, y + one texture coordinate.

class kivy.graphics.vertex_instructions.GraphicException

Bases: builtins.Exception

Exception raised when a graphics error is fired.

class kivy.graphics.vertex_instructions.Bezier

Bases: kivy.graphics.instructions.VertexInstruction

A 2d Bezier curve.

New in version 1.0.8.

Parameters:
points: list

List of points in the format (x1, y1, x2, y2…)

segments: int, defaults to 180

Define how many segments are needed for drawing the curve. The drawing will be smoother if you have many segments.

loop: bool, defaults to False

Set the bezier curve to join the last point to the first.

dash_length: int

Length of a segment (if dashed), defaults to 1.

dash_offset: int

Distance between the end of a segment and the start of the next one, defaults to 0. Changing this makes it dashed.

dash_length

Property for getting/setting the length of the dashes in the curve.

dash_offset

Property for getting/setting the offset between the dashes in the curve.

points

Property for getting/settings the points of the triangle.

Warning

This will always reconstruct the whole graphic from the new points list. It can be very CPU intensive.

segments

Property for getting/setting the number of segments of the curve.

class kivy.graphics.vertex_instructions.SmoothLine

Bases: kivy.graphics.vertex_instructions.Line

Experimental line using over-draw methods to get better anti-aliasing results. It has few drawbacks:

  • drawing a line with alpha will probably not have the intended result if the line crosses itself.
  • cap, joint and dash properties are not supported.
  • it uses a custom texture with a premultiplied alpha.
  • lines under 1px in width are not supported: they will look the same.

Warning

This is an unfinished work, experimental, and subject to crashes.

New in version 1.9.0.

overdraw_width

Determine the overdraw width of the line, defaults to 1.2.