fastmath.java

java 3d game jme 工程开发源代码

    }

    /**
     * Returns the log base E of a value.
     * @param fValue The value to log.
     * @return The log of fValue base E
     * @see java.lang.Math#log(double)
     */
    public static float log(float fValue) {
        return (float) Math.log(fValue);
    }
    
    /**
     * Returns the logarithm of value with given base, calculated as log(value)/log(base), 
     * so that pow(base, return)==value (contributed by vear)
     * @param value The value to log.
     * @param base Base of logarithm.
     * @return The logarithm of value with given base
     */
    public static float log(float value, float base) {
        return (float)(Math.log(value)/Math.log(base));
    }

    /**
     * Returns a number raised to an exponent power.  fBase^fExponent
     * @param fBase The base value (IE 2)
     * @param fExponent The exponent value (IE 3)
     * @return base raised to exponent (IE 8)
     * @see java.lang.Math#pow(double, double)
     */
    public static float pow(float fBase, float fExponent) {
        return (float) Math.pow(fBase, fExponent);
    }

    /**
     * Returns the value squared.  fValue ^ 2
     * @param fValue The vaule to square.
     * @return The square of the given value.
     */
    public static float sqr(float fValue) {
        return fValue * fValue;
    }

    /**
     * Returns the square root of a given value.
     * @param fValue The value to sqrt.
     * @return The square root of the given value.
     * @see java.lang.Math#sqrt(double)
     */
    public static float sqrt(float fValue) {
        return (float) Math.sqrt(fValue);
    }

    /**
     * Returns the tangent of a value.  If USE_FAST_TRIG is enabled, an approximate value
     * is returned.  Otherwise, a direct value is used.
     * @param fValue The value to tangent, in radians.
     * @return The tangent of fValue.
     * @see java.lang.Math#tan(double)
     */
    public static float tan(float fValue) {
        return (float) Math.tan(fValue);
    }

    /**
     * Returns 1 if the number is positive, -1 if the number is negative, and 0 otherwise
     * @param iValue The integer to examine.
     * @return The integer's sign.
     */
    public static int sign(int iValue) {
        if (iValue > 0) return 1;

        if (iValue < 0) return -1;

        return 0;
    }

    /**
     * Returns 1 if the number is positive, -1 if the number is negative, and 0 otherwise
     * @param fValue The float to examine.
     * @return The float's sign.
     */
    public static float sign(float fValue) {
        return Math.signum(fValue);
    }

    /**
     * Given 3 points in a 2d plane, this function computes if the points going from A-B-C
     * are moving counter clock wise.
     * @param p0 Point 0.
     * @param p1 Point 1.
     * @param p2 Point 2.
     * @return 1 If they are CCW, -1 if they are not CCW, 0 if p2 is between p0 and p1.
     */
    public static int counterClockwise(Vector2f p0,Vector2f p1,Vector2f p2){
        float dx1,dx2,dy1,dy2;
        dx1=p1.x-p0.x;
        dy1=p1.y-p0.y;
        dx2=p2.x-p0.x;
        dy2=p2.y-p0.y;
        if (dx1*dy2>dy1*dx2) return 1;
        if (dx1*dy2<dy1*dx2) return -1;
        if ((dx1*dx2 < 0) || (dy1*dy2 <0)) return -1;
        if ((dx1*dx1+dy1*dy1) < (dx2*dx2+dy2*dy2)) return 1;
        return 0;
    }

    /**
     * Test if a point is inside a triangle.  1 if the point is on the ccw side,
     * -1 if the point is on the cw side, and 0 if it is on neither.
     * @param t0 First point of the triangle.
     * @param t1 Second point of the triangle.
     * @param t2 Third point of the triangle.
     * @param p The point to test.
     * @return Value 1 or -1 if inside triangle, 0 otherwise.
     */
    public static int pointInsideTriangle(Vector2f t0,Vector2f t1,Vector2f t2,Vector2f p){
        int val1=counterClockwise(t0,t1,p);
        if (val1==0) return 1;
        int val2=counterClockwise(t1,t2,p);
        if (val2==0) return 1;
        if (val2!=val1) return 0;
        int val3=counterClockwise(t2,t0,p);
        if (val3==0) return 1;
        if (val3!=val1) return 0;
        return val3;
    }


    /**
     * Returns the determinant of a 4x4 matrix.
     */ 
    public static float determinant(double m00, double m01, double m02,
            double m03, double m10, double m11, double m12, double m13,
            double m20, double m21, double m22, double m23, double m30,
            double m31, double m32, double m33) {

        double det01 = m20 * m31 - m21 * m30;
        double det02 = m20 * m32 - m22 * m30;
        double det03 = m20 * m33 - m23 * m30;
        double det12 = m21 * m32 - m22 * m31;
        double det13 = m21 * m33 - m23 * m31;
        double det23 = m22 * m33 - m23 * m32;
        return (float) (m00 * (m11 * det23 - m12 * det13 + m13 * det12) - m01
                * (m10 * det23 - m12 * det03 + m13 * det02) + m02
                * (m10 * det13 - m11 * det03 + m13 * det01) - m03
                * (m10 * det12 - m11 * det02 + m12 * det01));
    }

    /**
     * Returns a random float between 0 and 1.
     * 
     * @return A random float between <tt>0.0f</tt> (inclusive) to
     *         <tt>1.0f</tt> (exclusive).
     */
    public static float nextRandomFloat() {
        return rand.nextFloat();
    }

    /**
     * Returns a random float between min and max.
     * 
     * @return A random int between <tt>min</tt> (inclusive) to
     *         <tt>max</tt> (inclusive).
     */
    public static int nextRandomInt(int min, int max) {
        return (int)(nextRandomFloat() * (max - min + 1)) + min;
    }

    public static int nextRandomInt() {
        return rand.nextInt();
    }

    /**
     * Converts a point from Spherical coordinates to Cartesian (using positive
     * Y as up) and stores the results in the store var.
     */
    public static Vector3f sphericalToCartesian(Vector3f sphereCoords,
            Vector3f store) {
        store.y = sphereCoords.x * FastMath.sin(sphereCoords.z);
        float a = sphereCoords.x * FastMath.cos(sphereCoords.z);
        store.x = a * FastMath.cos(sphereCoords.y);
        store.z = a * FastMath.sin(sphereCoords.y);

        return store;
    }

    /**
     * Converts a point from Cartesian coordinates (using positive Y as up) to
     * Spherical and stores the results in the store var. (Radius, Azimuth,
     * Polar)
     */
    public static Vector3f cartesianToSpherical(Vector3f cartCoords,
            Vector3f store) {
        if (cartCoords.x == 0)
            cartCoords.x = FastMath.FLT_EPSILON;
        store.x = FastMath
                .sqrt((cartCoords.x * cartCoords.x)
                        + (cartCoords.y * cartCoords.y)
                        + (cartCoords.z * cartCoords.z));
        store.y = FastMath.atan(cartCoords.z / cartCoords.x);
        if (cartCoords.x < 0)
            store.y += FastMath.PI;
        store.z = FastMath.asin(cartCoords.y / store.x);
        return store;
    }

    /**
     * Converts a point from Spherical coordinates to Cartesian (using positive
     * Z as up) and stores the results in the store var.
     */
    public static Vector3f sphericalToCartesianZ(Vector3f sphereCoords,
            Vector3f store) {
        store.z = sphereCoords.x * FastMath.sin(sphereCoords.z);
        float a = sphereCoords.x * FastMath.cos(sphereCoords.z);
        store.x = a * FastMath.cos(sphereCoords.y);
        store.y = a * FastMath.sin(sphereCoords.y);

        return store;
    }

    /**
     * Converts a point from Cartesian coordinates (using positive Z as up) to
     * Spherical and stores the results in the store var. (Radius, Azimuth,
     * Polar)
     */
    public static Vector3f cartesianZToSpherical(Vector3f cartCoords,
            Vector3f store) {
        if (cartCoords.x == 0)
            cartCoords.x = FastMath.FLT_EPSILON;
        store.x = FastMath
                .sqrt((cartCoords.x * cartCoords.x)
                        + (cartCoords.y * cartCoords.y)
                        + (cartCoords.z * cartCoords.z));
        store.z = FastMath.atan(cartCoords.z / cartCoords.x);
        if (cartCoords.x < 0)
            store.z += FastMath.PI;
        store.y = FastMath.asin(cartCoords.y / store.x);
        return store;
    }

    /**
     * Takes an value and expresses it in terms of min to max.
     * 
     * @param val -
     *            the angle to normalize (in radians)
     * @return the normalized angle (also in radians)
     */
    public static float normalize(float val, float min, float max) {
        if (Float.isInfinite(val) || Float.isNaN(val))
            return 0f;
        float range = max-min;
        while (val > max)
            val -= range;
        while (val < min)
            val += range;
        return val;
    }

    /**
     * @param x
     *            the value whose sign is to be adjusted.
     * @param y
     *            the value whose sign is to be used.
     * @return x with its sign changed to match the sign of y.
     */
    public static float copysign(float x, float y) {
        if (y >= 0 && x <= -0)
            return -x;
        else if (y < 0 && x >= 0)
            return -x;
        else
            return x;
    }
    
    /**
     * Take a float input and clamp it between min and max.
     * 
     * @param input
     * @param min
     * @param max
     * @return clamped input
     */
    public static float clamp(float input, float min, float max) {
        return (input < min) ? min : (input > max) ? max : input;
    }
}