Transforms
Moving, turning and scaling the coordinate system.
transform
transform()Saves the transform for a with block.
Think of it as “save the coordinate system”: inside the block, move, turn or scale freely; when the block ends, even through an exception or a return, the transform is back to what it was::
with kiln.transform():
kiln.translate(x, y)
kiln.rotate(angle)
kiln.rect(-10, -10, 20, 20)The transform is reset to identity at the start of every frame. A scope that spans methods (entered in update, left in draw) goes through contextlib.ExitStack.
Returns
| Name | Type | Description |
|---|---|---|
| _Transform | A context manager. |
translate
translate(x, y, z=0.0)Moves the origin of the coordinate system.
Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| x | float | Offset along x, in the current (possibly rotated or scaled) axes. | required |
| y | float | Offset along y. | required |
| z | float | Accepted and ignored: Kiln is 2D. | 0.0 |
rotate
rotate(radians)Rotates the coordinate system around the origin, in radians.
A positive angle turns clockwise on screen, because y points down: after rotate(math.radians(90)) a circle drawn at (50, 0) lands at (0, 50), below the origin. To rotate around a point, translate there first.
Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| radians | float | Angle in radians (math.radians converts degrees). |
required |
scale
scale(x, y=None)Scales the coordinate system around the origin.
Outline and line widths do not scale: stroke(width=) is in points on screen whatever the transform, including a non-uniform scale or a shear, so every edge of a stretched shape keeps the same thickness.
Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| x | float | Scale along x (and along y when y is omitted). |
required |
| y | float | None | Scale along y; None means uniform. | None |
reset_matrix
reset_matrix(m=None)Resets the transform to identity, or replaces it with m.
Inside with transform(): the end of the block still restores the transform from before it.
Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| m | np.ndarray | Sequence[Sequence[float]] | None | None for the identity, or a 3x3 (last row 0, 0, 1) or 2x3 array-like, column-vector convention, as returned by current_matrix. |
None |
Raises
| Name | Type | Description |
|---|---|---|
| ValueError | m is not an affine 3x3 or 2x3 matrix. |
current_matrix
current_matrix()Returns the current transform.
Returns
| Name | Type | Description |
|---|---|---|
| np.ndarray | A new 3x3 float64 numpy array in the column-vector convention, | |
| np.ndarray | [[m00, m01, tx], [m10, m11, ty], [0, 0, 1]]: a point (x, y) is |
|
| np.ndarray | placed at (M @ [x, y, 1])[:2]. Editing it does not change the |
|
| np.ndarray | transform; pass it to reset_matrix. |
apply_matrix
apply_matrix(m)Applies a matrix inside the current coordinate system.
The current transform becomes current @ m, like translate and friends.
Parameters
| Name | Type | Description | Default |
|---|---|---|---|
| m | np.ndarray | Sequence[Sequence[float]] | A 3x3 (last row 0, 0, 1) or 2x3 array-like, column-vector convention, as returned by current_matrix. |
required |
Raises
| Name | Type | Description |
|---|---|---|
| ValueError | m is not an affine 3x3 or 2x3 matrix. |