BSpline::calculate/derivative (and their calling functions) are silently failing for degre != 3

[omicron321]

libgdx/gdx/src/com/badlogic/gdx/math/BSpline.java

Lines 133 to 167 in bc31436

	/** Calculates the n-degree b-spline value for the given span (i) at the given position (u).
	* @param out The Vector to set to the result.
	* @param i The span (0<=i<spanCount) spanCount = continuous ? points.length : points.length - degree
	* @param u The position (0<=u<=1) on the span
	* @param points The control points
	* @param degree The degree of the b-spline
	* @param continuous If true the b-spline restarts at 0 when reaching 1
	* @param tmp A temporary vector used for the calculation
	* @return The value of out */
	public static <T extends Vector<T>> T calculate (final T out, final int i, final float u, final T[] points, final int degree,
	final boolean continuous, final T tmp) {
	switch (degree) {
	case 3:
	return cubic(out, i, u, points, continuous, tmp);
	}
	return out;
	}
	/** Calculates the n-degree b-spline derivative for the given span (i) at the given position (u).
	* @param out The Vector to set to the result.
	* @param i The span (0<=i<spanCount) spanCount = continuous ? points.length : points.length - degree
	* @param u The position (0<=u<=1) on the span
	* @param points The control points
	* @param degree The degree of the b-spline
	* @param continuous If true the b-spline restarts at 0 when reaching 1
	* @param tmp A temporary vector used for the calculation
	* @return The value of out */
	public static <T extends Vector<T>> T derivative (final T out, final int i, final float u, final T[] points, final int degree,
	final boolean continuous, final T tmp) {
	switch (degree) {
	case 3:
	return cubic_derivative(out, i, u, points, continuous, tmp);
	}
	return out;
	}

[NathanSweet]

I assume having a degree parameter that only supports 3 is because the author didn't have time to implement others. Contributions are welcome.

[tommyettinger]

I think the problem is more that the spline doesn't do anything when degree is not 3 (hence "silently" failing), and it isn't documented that 3 is the only spline degree that does anything. Is the solution here for someone to implement other degrees? Would it be enough to document that degree should always be 3?

[NathanSweet]

Aye, we should document and throw illegal argument exception if it's not 3 until the time that someone implements other values.

Edit: oops, made that change in the texture atlas improvement PR. Will just wait for that to be merged.

[tommyettinger]

Now that the texture atlas PR is merged, the requirement for spline degree to be 3 is documented and the method throws an IllegalArgumentException if degree is not 3. If anyone intends to implement more degrees later, we could leave this open until those are ready, but otherwise this could maybe be closed.