public void resetUniformsNotSetByCurrent() {
        int size = uniforms.size();
        for (int i = 0; i < size; i++) {
            Uniform u = uniforms.getValue(i);
            if (!u.isSetByCurrentMaterial()) {
                u.clearValue();
            }
        }
    }
Resets all uniforms that do not have the "set-by-current-material" flag
to their default value (usually all zeroes or false).
When a uniform is modified, that flag is set, to remove the flag,
use {@link #clearUniformsSetByCurrentFlag() }.
jme3-core/src/main/java/com/jme3/shader/Shader.java