com.github.mathiewz.slick.geom.Circle Maven / Gradle / Ivy

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The main purpose of this libraryis to modernize and maintain the slick2D library.
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package com.github.mathiewz.slick.geom;

/**
 * A simple Circle geometry
 *
 * @author Kevin Glass
 */
public strictfp class Circle extends Ellipse {
    /** The radius of the circle */
    public float radius;

    /**
     * Create a new circle based on its radius
     *
     * @param centerPointX
     *            The x location of the center of the circle
     * @param centerPointY
     *            The y location of the center of the circle
     * @param radius
     *            The radius of the circle
     */
    public Circle(float centerPointX, float centerPointY, float radius) {
        this(centerPointX, centerPointY, radius, DEFAULT_SEGMENT_COUNT);
    }

    /**
     * Create a new circle based on its radius
     *
     * @param centerPointX
     *            The x location of the center of the circle
     * @param centerPointY
     *            The y location of the center of the circle
     * @param radius
     *            The radius of the circle
     * @param segmentCount
     *            The number of segments to build the circle out of
     */
    public Circle(float centerPointX, float centerPointY, float radius, int segmentCount) {
        super(centerPointX, centerPointY, radius, radius, segmentCount);
        x = centerPointX - radius;
        y = centerPointY - radius;
        this.radius = radius;
        boundingCircleRadius = radius;
    }

    /**
     * Get the x coordinate of the centre of the circle
     *
     * @return The x coordinate of the centre of the circle
     */
    @Override
    public float getCenterX() {
        return getX() + radius;
    }

    /**
     * Get the y coordinate of the centre of the circle
     *
     * @return The y coordinate of the centre of the circle
     */
    @Override
    public float getCenterY() {
        return getY() + radius;
    }

    /**
     * Get the coordinates of the center of the circle
     *
     * @return 2-element array with the center of the circle.
     */
    @Override
    public float[] getCenter() {
        return new float[] { getCenterX(), getCenterY() };
    }

    /**
     * Set the radius of this circle
     *
     * @param radius
     *            The radius of this circle
     */
    public void setRadius(float radius) {
        if (radius != this.radius) {
            pointsDirty = true;
            this.radius = radius;
            setRadii(radius, radius);
        }
    }

    /**
     * Get the radius of the circle
     *
     * @return The radius of the circle
     */
    public float getRadius() {
        return radius;
    }

    /**
     * Check if this circle touches another
     *
     * @param shape
     *            The other circle
     * @return True if they touch
     */
    @Override
    public boolean intersects(Shape shape) {
        if (shape instanceof Circle) {
            Circle other = (Circle) shape;
            float totalRad2 = getRadius() + other.getRadius();

            if (Math.abs(other.getCenterX() - getCenterX()) > totalRad2) {
                return false;
            }
            if (Math.abs(other.getCenterY() - getCenterY()) > totalRad2) {
                return false;
            }

            totalRad2 *= totalRad2;

            float dx = Math.abs(other.getCenterX() - getCenterX());
            float dy = Math.abs(other.getCenterY() - getCenterY());

            return totalRad2 >= dx * dx + dy * dy;
        } else if (shape instanceof Rectangle) {
            return intersects((Rectangle) shape);
        } else {
            return super.intersects(shape);
        }
    }

    /**
     * Check if a point is contained by this circle
     *
     * @param x
     *            The x coordinate of the point to check
     * @param y
     *            The y coorindate of the point to check
     * @return True if the point is contained by this circle
     */
    @Override
    public boolean contains(float x, float y) {
        float xDelta = x - getCenterX(), yDelta = y - getCenterY();
        return xDelta * xDelta + yDelta * yDelta < getRadius() * getRadius();
    }

    /**
     * @see com.github.mathiewz.slick.geom.Ellipse#findCenter()
     */
    @Override
    protected void findCenter() {
        center = new float[2];
        center[0] = x + radius;
        center[1] = y + radius;
    }

    /**
     * @see com.github.mathiewz.slick.geom.Ellipse#calculateRadius()
     */
    @Override
    protected void calculateRadius() {
        boundingCircleRadius = radius;
    }

    /**
     * Check if this circle touches a rectangle
     *
     * @param other
     *            The rectangle to check against
     * @return True if they touch
     */
    private boolean intersects(Rectangle other) {
        Rectangle box = other;
        Circle circle = this;

        if (box.contains(x + radius, y + radius)) {
            return true;
        }

        float x1 = box.getX();
        float y1 = box.getY();
        float x2 = box.getX() + box.getWidth();
        float y2 = box.getY() + box.getHeight();

        Line[] lines = new Line[4];
        lines[0] = new Line(x1, y1, x2, y1);
        lines[1] = new Line(x2, y1, x2, y2);
        lines[2] = new Line(x2, y2, x1, y2);
        lines[3] = new Line(x1, y2, x1, y1);

        float r2 = circle.getRadius() * circle.getRadius();

        Vector2f pos = new Vector2f(circle.getCenterX(), circle.getCenterY());

        for (int i = 0; i < 4; i++) {
            float dis = lines[i].distanceSquared(pos);
            if (dis < r2) {
                return true;
            }
        }

        return false;
    }
}