com.almasb.fxgl.physics.box2d.collision.AABB Maven / Gradle / Ivy
/*
* FXGL - JavaFX Game Library. The MIT License (MIT).
* Copyright (c) AlmasB ([email protected]).
* See LICENSE for details.
*/
package com.almasb.fxgl.physics.box2d.collision;
import com.almasb.fxgl.core.math.Vec2;
import com.almasb.fxgl.physics.box2d.common.JBoxSettings;
import com.almasb.fxgl.physics.box2d.common.JBoxUtils;
import com.almasb.fxgl.physics.box2d.pooling.IWorldPool;
import static com.almasb.fxgl.core.math.FXGLMath.abs;
/**
* An axis-aligned bounding box.
*/
public final class AABB {
/**
* Bottom left vertex of bounding box.
*/
public final Vec2 lowerBound;
/**
* Top right vertex of bounding box.
*/
public final Vec2 upperBound;
/**
* Creates the default object, with vertices at 0,0 and 0,0.
*/
public AABB() {
lowerBound = new Vec2();
upperBound = new Vec2();
}
/**
* Copies from the given object.
*
* @param copy the object to copy from
*/
public AABB(AABB copy) {
this(copy.lowerBound, copy.upperBound);
}
/**
* Creates an AABB object using the given bounding vertices.
*
* @param lowerVertex the bottom left vertex of the bounding box
* @param upperVertex the top right vertex of the bounding box
*/
public AABB(Vec2 lowerVertex, Vec2 upperVertex) {
this.lowerBound = lowerVertex.clone(); // clone to be safe
this.upperBound = upperVertex.clone();
}
/**
* Sets this object from the given object.
*
* @param aabb the object to copy from
*/
public void set(AABB aabb) {
Vec2 v = aabb.lowerBound;
lowerBound.x = v.x;
lowerBound.y = v.y;
Vec2 v1 = aabb.upperBound;
upperBound.x = v1.x;
upperBound.y = v1.y;
}
/**
* @return the center of the AABB
*/
public Vec2 getCenter() {
return new Vec2(lowerBound)
.addLocal(upperBound)
.mulLocal(0.5);
}
/**
* @return the extents of the AABB (half-widths)
*/
public Vec2 getExtents() {
return new Vec2(upperBound)
.subLocal(lowerBound)
.mulLocal(0.5);
}
/**
* @return the perimeter length
*/
public float getPerimeter() {
return 2.0f * (upperBound.x - lowerBound.x + upperBound.y - lowerBound.y);
}
/**
* Combine two AABBs into this one.
*/
public void combine(AABB aabb1, AABB aabb2) {
lowerBound.x = aabb1.lowerBound.x < aabb2.lowerBound.x ? aabb1.lowerBound.x : aabb2.lowerBound.x;
lowerBound.y = aabb1.lowerBound.y < aabb2.lowerBound.y ? aabb1.lowerBound.y : aabb2.lowerBound.y;
upperBound.x = aabb1.upperBound.x > aabb2.upperBound.x ? aabb1.upperBound.x : aabb2.upperBound.x;
upperBound.y = aabb1.upperBound.y > aabb2.upperBound.y ? aabb1.upperBound.y : aabb2.upperBound.y;
}
/**
* Combines another aabb with this one.
*/
public void combine(AABB aabb) {
lowerBound.x = lowerBound.x < aabb.lowerBound.x ? lowerBound.x : aabb.lowerBound.x;
lowerBound.y = lowerBound.y < aabb.lowerBound.y ? lowerBound.y : aabb.lowerBound.y;
upperBound.x = upperBound.x > aabb.upperBound.x ? upperBound.x : aabb.upperBound.x;
upperBound.y = upperBound.y > aabb.upperBound.y ? upperBound.y : aabb.upperBound.y;
}
/**
* @return true if this aabb contain the provided AABB
*/
public boolean contains(AABB aabb) {
return lowerBound.x <= aabb.lowerBound.x && lowerBound.y <= aabb.lowerBound.y
&& aabb.upperBound.x <= upperBound.x && aabb.upperBound.y <= upperBound.y;
}
/**
* From Real-time Collision Detection, p179.
*/
public boolean raycast(final RayCastOutput output, final RayCastInput input, IWorldPool argPool) {
float tmin = -Float.MAX_VALUE;
float tmax = Float.MAX_VALUE;
final Vec2 p = argPool.popVec2();
final Vec2 d = argPool.popVec2();
final Vec2 absD = argPool.popVec2();
final Vec2 normal = argPool.popVec2();
p.set(input.p1);
d.set(input.p2).subLocal(input.p1);
absD.x = abs(d.x);
absD.y = abs(d.y);
// x then y
if (absD.x < JBoxSettings.EPSILON) {
// Parallel.
if (p.x < lowerBound.x || upperBound.x < p.x) {
argPool.pushVec2(4);
return false;
}
} else {
final float inv_d = 1.0f / d.x;
float t1 = (lowerBound.x - p.x) * inv_d;
float t2 = (upperBound.x - p.x) * inv_d;
// Sign of the normal vector.
float s = -1.0f;
if (t1 > t2) {
final float temp = t1;
t1 = t2;
t2 = temp;
s = 1.0f;
}
// Push the min up
if (t1 > tmin) {
normal.setZero();
normal.x = s;
tmin = t1;
}
// Pull the max down
tmax = JBoxUtils.min(tmax, t2);
if (tmin > tmax) {
argPool.pushVec2(4);
return false;
}
}
if (absD.y < JBoxSettings.EPSILON) {
// Parallel.
if (p.y < lowerBound.y || upperBound.y < p.y) {
argPool.pushVec2(4);
return false;
}
} else {
final float inv_d = 1.0f / d.y;
float t1 = (lowerBound.y - p.y) * inv_d;
float t2 = (upperBound.y - p.y) * inv_d;
// Sign of the normal vector.
float s = -1.0f;
if (t1 > t2) {
final float temp = t1;
t1 = t2;
t2 = temp;
s = 1.0f;
}
// Push the min up
if (t1 > tmin) {
normal.setZero();
normal.y = s;
tmin = t1;
}
// Pull the max down
tmax = JBoxUtils.min(tmax, t2);
if (tmin > tmax) {
argPool.pushVec2(4);
return false;
}
}
// Does the ray start inside the box?
// Does the ray intersect beyond the max fraction?
if (tmin < 0.0f || input.maxFraction < tmin) {
argPool.pushVec2(4);
return false;
}
// Intersection.
output.fraction = tmin;
output.normal.x = normal.x;
output.normal.y = normal.y;
argPool.pushVec2(4);
return true;
}
public static boolean testOverlap(AABB a, AABB b) {
if (b.lowerBound.x - a.upperBound.x > 0 || b.lowerBound.y - a.upperBound.y > 0
|| a.lowerBound.x - b.upperBound.x > 0 || a.lowerBound.y - b.upperBound.y > 0) {
return false;
}
return true;
}
@Override
public String toString() {
return "AABB[" + lowerBound + " . " + upperBound + "]";
}
}
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