Check precisely if two rectangles with double coordinates intersect

Question

I was playing arround with hitboxes and ended up with following data:

final double targetSmallestX = targetCenter.getX() - targetHalfWidth;
final double targetSmallestY = targetCenter.getY() - targetHalfHeight;
final double targetHighestX = targetCenter.getX() + targetHalfWidth;
final double targetHighestY = targetCenter.getY() + targetHalfHeight;
final double sourceSmallestX = sourceCenter.getX() - sourceHalfWidth;
final double sourceSmallestY = sourceCenter.getY() - sourceHalfHeight;
final double sourceHighestX = sourceCenter.getX() + sourceHalfWidth;
final double sourceHighestY = sourceCenter.getY() + sourceHalfHeight;

What i want to do is to check, if the two given rectangles target and source are intersecting with each other. Could have done it like this

Rectangle target = new Rectangle(targetSmallestX, target.width, targetSmallestY, target.height);
Rectangle source = new Rectangle(sourceSmallestX, source.width, sourceSmallestY, source.height);
target.intersect(source);

But this would require me to work with integers.
All the algorithms I came up with seemed too long and complicated for such a seemingly simple task. Does anyone have an idea for a smart approach for this?

EDIT:
Current approach

(targetSmallestX < sourceSmallestX + this.width)
&& (sourceSmallestX < (targetSmallestX + target.width))
&& (targetSmallestY < sourceSmallestY + this.height)
&& (sourceSmallestY < targetSmallestY + target.height);

Does this check leave any possible constellations in which it wouldn't work correctly?

Take a look at the source code for Intersect here: referencesource.microsoft.com/#System.Drawing/commonui/System/… — Ian Mercer
– Ian Mercer, Commented Apr 21, 2018 at 21:35
Two rectangles intersect if and only if their x-values overlap, and their y-values overlap. You can write an "overlap" function that accepts range1Start, range1Width, range2Start, and range2Width and returns whether those ranges intersect. Then, call that twice for x-values and y-values. — k_ssb
– k_ssb, Commented Apr 21, 2018 at 22:51
@userunknown yes. I am not going to go through the trouble of calculating that stuff with angles — Basti
– Basti, Commented Apr 22, 2018 at 15:03

k_ssb · Accepted Answer · 2018-04-22 15:07:59Z

1

In Java, you can use java.awt.geom.Rectangle2D which represents coordinates with floating-point precision. Precisely, its inner class java.awt.geom.Rectangle2D.Double uses double to represent the coordinates.

Rectangle2D target = new Rectangle2D.Double(targetSmallestX, targetSmallestY, target.width, target.height);
Rectangle2D source = new Rectangle2D.Double(sourceSmallestX, sourceSmallestY, source.width, source.height);
target.intersect(source);

answered Apr 22, 2018 at 15:07

k_ssb

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1 Comment

Basti Over a year ago

Ty. Didn't know Rectangle has a Double implementation.

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