public void setSpotInnerAngle(float spotInnerAngle) {
        if (spotInnerAngle < 0f || spotInnerAngle >= FastMath.HALF_PI) {
            throw new IllegalArgumentException("spot angle must be between 0 and pi/2");
        }
        this.spotInnerAngle = spotInnerAngle;
        computeAngleParameters();
    }
Sets the inner angle of the cone of influence.
<p>
Must be between 0 and pi/2.
<p>
This angle is the angle between the spot direction axis and the inner border of the cone of influence.

@param spotInnerAngle the desired angle (in radians, &ge;0, &le;Pi/2)
jme3-core/src/main/java/com/jme3/light/SpotLight.java