Nov 232013
 

We have seen in previous article 8 how to perform pixel collision.
Altough it worked perfectly, it only worked on non rotated shapes.

But in some cases, your shape will rotate (like a car in a racing game – see article « A racing car game »).

To perform pixel collision for a rotated shape, here below the steps :

-you first need to draw a rotated rectangle around your shape
-you then need to draw a bounding rectanle around that rotated rectangle (also called AABB : Axis Aligned Bounding Box)
-finally you can check whether 2 AABB intersects, and if so, if in the intersected region, we have 2 non transparent pixels (colliding) or not

The source code : XNA_DEMO_18
Note : the project contains a class named primitives2d which is used only to draw lines/rectangles around my objects.

Lets illustrate this with some screenshots.

Lets rotate our rectangle along with my rocket
pixel2

Lets define our bounding box
pixel3

Despite bounding boxes intersecting, we dont detect collision yet
pixel4

Here we go ! In the intersection region, there are 2 non transparent pixels
pixel5

 Posted by at 17 h 41 min

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