Draw circles/particles with different radii in GGUI

[YouJiacheng]

Concisely describe the proposed feature
Currently canvas.circles and scene.particles only supports a single scalar radius, prevent users drawing many circles/particles with different radii in batch. I would like to draw many circles/particles with different radii efficiently, using one canvas.circles or scene.particles call.

Describe the solution you'd like (if any)
Allow parameter radius to be a taichi field.

Additional comments
ti.GUI.circles allows parameter radius to be a numpy ndarray. BTW, the documentation seems outdated:

taichi/python/taichi/ui/gui.py

Lines 355 to 365 in 449a7f6

	def circles(self,
	pos,
	radius=1,
	color=0xFFFFFF,
	palette=None,
	palette_indices=None):
	"""Draws a list of circles on canvas.
	Args:
	pos (numpy.array): The positions of the circles.
	radius (Number, optional): The radius of the circles in pixel. Default is 1.

taichi/python/taichi/ui/gui.py

Lines 430 to 434 in 449a7f6

	if isinstance(radius, np.ndarray):
	assert radius.shape == (n, )
	radius = np.ascontiguousarray(radius.astype(np.float32))
	radius_array = int(radius.ctypes.data)
	radius_single = 0

It should be radius (Union[Number, np.array], optional) like ti.GUI.arrows.

[YouJiacheng]

Hmmm. I don't think this issue should be closed by a docstring fix.

1. Does the canvas.circles really support array radius? And I afraid it should be taichi field instead of numpy array in GGUI.
2. What about scene.particles?

[ailzhang]

cc: @neozhaoliang

[bobcao3]

Duplicate of #3888 ?