Forum Archive

I need to know how to use collision detection and how to give an object opacity. Could someone please post some code???
Thx
—Webmaster4o

Look at the gists in this thread for code that does collision detection:

http://omz-forums.appspot.com/pythonista/post/4695137988902912

Changing a scene.Layer.alpha value will change that Layer's transparency / opacity.

alpha = 0.0 means the Layer is fully transparent

alpha = 1.0 means the Layer is fully opaque

import scene

class MyScene(scene.Scene):
    def __init__(self):
        scene.run(self)

    def setup(self):
        center = self.bounds.center()
        self.layer = scene.Layer(scene.Rect(center.x - 64, center.y - 64, 128, 128))
        self.layer.alpha = 0  # 0.0 = fully transparent, 1.0 = fully opaque
        self.layer.background = scene.Color(1, 0, 0)
        self.layer.image = 'Snake'
        self.add_layer(self.layer)

    def draw(self):
        scene.background(0, 0, 0)
        self.root_layer.update(self.dt)
        self.root_layer.draw()
        self.layer.alpha += .01  # cycle the layer's alpha value
        if self.layer.alpha > 1:
            self.layer.alpha = 0

MyScene()

scene.Color objects also have an alpha value that you can mess with: scene.Color(red, green, blue, alpha)

If you want collision detection for Rect objects, use the Rect.intersects(other_rect) method. It returns a bool value. An example:

from scene import *
class MyScene(Scene):
   def draw(self):
        fill(1, 0, 0)
        rect(0, 0, 50, 75)
        r1 = Rect(0, 0, 50, 75)
        rect(0, 0, 50, 25)
        r2 = Rect(0, 0, 50, 25)
        if r1.intersects(r2):
            print "R1 intersects R2"
run(MyScene()) # Please note that this script will continuously produce output in the console, so stop the script quickly.

This only works for Rect objects.
I hope that helps!

This works with circles:

from scene import *

def centered_ellipse(x, y, w, h):
    ellipse(x-w/2, y-h/2, w, h)

class MyScene (Scene):
    def setup(self):
        self.pos = Point(self.size.w/2, self.size.h/2)
        self.pos2 = Point(0, 0)

    def draw(self):
        background(0, 0, 0)
        centered_ellipse(self.pos.x, self.pos.y, 100, 100)
        centered_ellipse(self.pos2.x, self.pos2.y, 100, 100)
        for touch in self.touches.values():
            self.pos2 = touch.location
            if self.pos.distance(self.pos2) < 100:
                fill(1, 0, 0)
            else: 
                fill(1, 1, 1)

run(MyScene())