How to draw a circle segment (pie) in Scene?

Oscar

Not the most straight forward bit of Code, but it works:

def draw(self):
	with ui.ImageContext(200, 200) as ctx:
		path = ui.Path()
		path.move_to(180, 100)
		path.add_arc(100, 100,  80, 0, radians(170))
		path.line_width = 5
		ui.set_color('blue')
		path.stroke()
		ui_image = ctx.get_image()
	pil_image = Image.open(io.BytesIO(ui_image.to_png()))
	scene_image = load_pil_image(pil_image)
	image(scene_image)

Webmaster4o

I have also been frustrated in the past by the lack of drawing functionality in scene. It lacks simple functions like drawing a polygon from a list of points. I'd love for scene to have all the functionality of PIL.ImageDraw.

Oscar

I think that right now the way to do it is using a PathNode. The old way of doing explicit drawing is not very efficient.

Edit: I meant ShapeNode when I wrote PathNode...

omz

You can either use a ShapeNode if you're using the new scene API, or the triangle_strip function (also new in 2.0) if you're working in "legacy mode".

Olaf

Example:

# coding: utf-8

import math, scene, ui

def circle_segment_path(r, angle):
    '''Path for circle segment (i.e. 'pizza slice') of radius r and angle degrees'''
    path = ui.Path()
    path.move_to(0, 0)
    path.line_to(r, 0)
    path.add_arc(0, 0, r, 0, -math.radians(angle), False)
    path.line_to(0, 0)
    return path
    
def circle_segment_shape(point, r, angle):
    '''Blue & red shape for circle segment of radius r and angle degrees at point'''
    return scene.ShapeNode(path=circle_segment_path(r, angle),
                           fill_color='blue', stroke_color='red', position=point)

class MyScene (scene.Scene):
    def setup(self):
        self.add_child(circle_segment_shape(self.size/2, 200, 45))

if __name__ == '__main__':
    scene.run(MyScene(), show_fps=True)```

Olaf

Or if you want more 'pizza':

class MyScene (scene.Scene):
    def setup(self):
        for x in xrange(0, int(self.size.w)+50, 50):
            for y in xrange(0, int(self.size.h)+50, 50):            
                self.add_child(circle_segment_shape((x, y), 50, 45))

upwart

@omz
I am trying to work out how to use triangle_strip, but I can't get it to work. For now all I want to do is draw a (solid) triangle.
If I try triangle_strip(((0,0),(10,0),(0,10))) I get a "Type error: expected sequence". Same if I close the sequence with a (0,0) tuple.

An example would be very helpful.

upwart

Thanks for all thoce nice examples with the new node objects. But for me the classical render loop is a must, because what am actuelly doing is prototyping an animation film that finally will be ported to Python on a Windows machine, most likely with PyGame or just plain PIL. Therefor the node objects are not an option to me, although I really like the concept.

Oscar

The list of points in your example is not strictly a list, it is a tuple of tuples.

I haven't tried it myself, but does triangle_strip([(0,0),(10,0),(0,10)]) work?

upwart

@Oscar
No also the list of tuples as you suggest does not work. Alas.

Olaf

Although the documentation states scene_drawing.triangle_strip(points[, tex_coords, image_name]), it seems tex_coords are mandatory (and of equal length as points). image_name is optional. I don't fully comprehend the logic at this time.
scene_drawing contains a call to triangle_strip in image_quad.

upwart

@Olaf
Super! I just added a list of tuples with random values and voilà it works!
Thanks.