CODEWITHSUNDEEP
javalwjgl
Caspermartijn
Caspermartijn

Reputation: 37

Rotating a hitbox and detect that rotation in a calculation

I am making a 3D Java game but i have got problems when rotating a hitbox. I, upon this point, only used a method which detects if a Vector3f is in a box.

But in my game I want to rotate houses, for example, so that method won't work. I could use circulair hitboxes but that wouldn't work for every instance of objects.

So far i have used this simple calculation to detect if a location is in a hitbox.

    public boolean isinbox(Vector3f pos) {
    Vector3f entPos = ent.getPosition();

    float x1 = entPos.x + xOffset;
    float z1 = entPos.z + zOffset;
    float y1 = entPos.y + yOffset;

    float x2 = entPos.x - xOffset;
    float z2 = entPos.z - zOffset;
    float y2 = entPos.y;

    return pos.x < x1 && pos.x > x2 && pos.z < z1 && pos.z > z2 && pos.y > y2 && pos.y < y1;
}

This works in many ways, but I can't figure out how to rotate them and still be able to detect it. The xOffset is the ofset if side a to the center and negative side b to the center.

How would I be able to rotate a hitbox and detect if an Vector is in it?

Upvotes: 1

Views: 1004

Answers (1)

Kylon Tyner
Kylon Tyner

Reputation: 391

There are a couple of ways of getting around this issue and one (or more) ways of solving this issue:

Solving It

SAT Collision

SAT Stands for Separating Axis Theorem. TutsPlus and MetaSoftware are great websites to learn how it works and how to implement it.

The Separating Axis Theorem (SAT for short) essentially states if you are able to draw a line to separate two polygons, then they do not collide. It's that simple. (gamedevelopment.tutsplus.com)


Here is the basic idea:

enter image description here


It can also be used for more complex shapes: enter image description here

Getting Around It

AABB Collision

This is done by assuming that collisions will only ever happen on the X/Y axis (never on an axis defined by an arbitrary line).

Here is an example of what this looks like: enter image description here

Therefore, you must define this axis-aligned hitbox by using the minimum X-and-Y values and the maximum X-and-Y values of the original box.

Circle Collision

This is a much simpler collision check which only detects when two objects are within a certain distance of each other.

Here is an example of what this looks like:
enter image description here

The way this works is that if the distance between the two objects is less than the sum of each circle's radius, then the objects are colliding.

Using an External Library

Upvotes: 3

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