Revisions to Collision between AABB and Circle

Fix pseudo code algorithm, signs and distance calculation were incorrect

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edit approved Mar 18, 2024 at 23:51

1

To detect collisions between a circle and an AABB, you should find the closest point from the AABB to the circle. You can run the below code snippet and try to move the purple point which represents the AABB center to watch the position of the closest point.

<iframe src="https://www.desmos.com/calculator/u32th8uhli?embed" width="500px" height="500px" style="border: 1px solid #ccc" frameborder=0></iframe>

The math behind it is to clamp the distance from AABB to circle on each axis separately. The value will be clamped on each axis if the distance is greater than the extent(half-width or height) or less than the negative extent. Like the below figure shows:

(Forgive my clumsy finger).
The pseudo-code is:

func CheckCollision() {
    vector3 distance = AABBCircle.Center - CircleAABB.Center;
    //Clamp(value,min,max)
    vector3 clampDst = Clamp(distance, -AABB.Bounds, AABB.Bounds);
    vector3 closestPoint = AABB.Center + clampDst;
    return Distance(closestPoint -, Circle.Center).SqrMagnitude ><= Circle.Radius;
}

To detect collisions between a circle and an AABB, you should find the closest point from the AABB to the circle. You can run the below code snippet and try to move the purple point which represents the AABB center to watch the position of the closest point.

<iframe src="https://www.desmos.com/calculator/u32th8uhli?embed" width="500px" height="500px" style="border: 1px solid #ccc" frameborder=0></iframe>

The math behind it is to clamp the distance from AABB to circle on each axis separately. The value will be clamped on each axis if the distance is greater than the extent(half-width or height) or less than the negative extent. Like the below figure shows:

(Forgive my clumsy finger).
The pseudo-code is:

func CheckCollision(){
    vector3 distance = AABB.Center - Circle.Center;
    //Clamp(value,min,max)
    vector3 clampDst = Clamp(distance, -AABB.Bounds, AABB.Bounds);
    vector3 closestPoint = AABB.Center + clampDst;
    return (closestPoint - Circle.Center).SqrMagnitude > Circle.Radius;
}

To detect collisions between a circle and an AABB, you should find the closest point from the AABB to the circle. You can run the below code snippet and try to move the purple point which represents the AABB center to watch the position of the closest point.

<iframe src="https://www.desmos.com/calculator/u32th8uhli?embed" width="500px" height="500px" style="border: 1px solid #ccc" frameborder=0></iframe>

The math behind it is to clamp the distance from AABB to circle on each axis separately. The value will be clamped on each axis if the distance is greater than the extent(half-width or height) or less than the negative extent. Like the below figure shows:

(Forgive my clumsy finger).
The pseudo-code is:

func CheckCollision() {
    vector3 distance = Circle.Center - AABB.Center;
    vector3 clampDst = Clamp(distance, -AABB.Bounds, AABB.Bounds);
    vector3 closestPoint = AABB.Center + clampDst;
    return Distance(closestPoint, Circle.Center) <= Circle.Radius;
}

added 1 character in body

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edited Jan 4, 2020 at 15:06

Ghoster

61
1
3

To detect collisions between a circle and an AABB, you should find the closest point from the AABB to the circle. You can run the below code snippet and try to move the purple point which represents the AABB center to watch the position of the closest point.

<iframe src="https://www.desmos.com/calculator/u32th8uhli?embed" width="500px" height="500px" style="border: 1px solid #ccc" frameborder=0></iframe>

ToThe math behind it is to clamp the distance from AABB to circle on each axis separately. The value will be clamped on each axis if the distance is greater than the extent(half-width or height) or less than the negative extent. Like the below figure shows:

(Forgive my clumsy finger).
The pseudo-code is:

func CheckCollision(){
    vector3 distance = AABB.Center - Circle.Center;
    //Clamp(value,min,max)
    vector3 clampDst = Clamp(distance, -AABB.Bounds, AABB.Bounds);
    vector3 closestPoint = AABB.Center + clampDst;
    return (closestPoint - Circle.Center).SqrMagnitude > Circle.Radius;
}

To detect collisions between a circle and an AABB, you should find the closest point from the AABB to the circle. You can run the below code snippet and try to move the purple point which represents the AABB center to watch the position of the closest point.

<iframe src="https://www.desmos.com/calculator/u32th8uhli?embed" width="500px" height="500px" style="border: 1px solid #ccc" frameborder=0></iframe>

To math behind it is to clamp the distance from AABB to circle on each axis separately. The value will be clamped on each axis if the distance is greater than the extent(half-width or height) or less than the negative extent. Like the below figure shows:

(Forgive my clumsy finger).
The pseudo-code is:

func CheckCollision(){
    vector3 distance = AABB.Center - Circle.Center;
    //Clamp(value,min,max)
    vector3 clampDst = Clamp(distance, -AABB.Bounds, AABB.Bounds);
    vector3 closestPoint = AABB.Center + clampDst;
    return (closestPoint - Circle.Center).SqrMagnitude > Circle.Radius;
}

To detect collisions between a circle and an AABB, you should find the closest point from the AABB to the circle. You can run the below code snippet and try to move the purple point which represents the AABB center to watch the position of the closest point.

<iframe src="https://www.desmos.com/calculator/u32th8uhli?embed" width="500px" height="500px" style="border: 1px solid #ccc" frameborder=0></iframe>

The math behind it is to clamp the distance from AABB to circle on each axis separately. The value will be clamped on each axis if the distance is greater than the extent(half-width or height) or less than the negative extent. Like the below figure shows:

(Forgive my clumsy finger).
The pseudo-code is:

func CheckCollision(){
    vector3 distance = AABB.Center - Circle.Center;
    //Clamp(value,min,max)
    vector3 clampDst = Clamp(distance, -AABB.Bounds, AABB.Bounds);
    vector3 closestPoint = AABB.Center + clampDst;
    return (closestPoint - Circle.Center).SqrMagnitude > Circle.Radius;
}

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answered Jan 4, 2020 at 14:40

Ghoster

61
1
3

To detect collisions between a circle and an AABB, you should find the closest point from the AABB to the circle. You can run the below code snippet and try to move the purple point which represents the AABB center to watch the position of the closest point.

<iframe src="https://www.desmos.com/calculator/u32th8uhli?embed" width="500px" height="500px" style="border: 1px solid #ccc" frameborder=0></iframe>

To math behind it is to clamp the distance from AABB to circle on each axis separately. The value will be clamped on each axis if the distance is greater than the extent(half-width or height) or less than the negative extent. Like the below figure shows:

(Forgive my clumsy finger).
The pseudo-code is:

func CheckCollision(){
    vector3 distance = AABB.Center - Circle.Center;
    //Clamp(value,min,max)
    vector3 clampDst = Clamp(distance, -AABB.Bounds, AABB.Bounds);
    vector3 closestPoint = AABB.Center + clampDst;
    return (closestPoint - Circle.Center).SqrMagnitude > Circle.Radius;
}

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