private float collideWithVertex(Vector3f sCenter, Vector3f sVelocity,
                                    float velocitySquared, Vector3f vertex, float t) {
        // A = velocity * velocity
        // B = 2 * (velocity . (center - vertex));
        // C = ||vertex - center||^2 - 1f;

        temp1.set(sCenter).subtractLocal(vertex);
        float a = velocitySquared;
        float b = 2f * sVelocity.dot(temp1);
        float c = temp1.negateLocal().lengthSquared() - 1f;
        float newT = getLowestRoot(a, b, c, t);

//        float A = velocitySquared;
//        float B = sCenter.subtract(vertex).dot(sVelocity) * 2f;
//        float C = vertex.subtract(sCenter).lengthSquared() - 1f;
//
//        float newT = getLowestRoot(A, B, C, Float.MAX_VALUE);
//        if (newT > 1.0f)
//            newT = Float.NaN;

        return newT;
    }
No longer public.

@author Kirill Vainer
jme3-core/src/main/java/com/jme3/collision/SweepSphere.java