code: public void setMat4(String key, float x1, float y1, float z1, float w1,
                          float x2, float y2, float z2, float w2, float x3, float y3,
                          float z3, float w3, float x4, float y4, float z4, float w4)
      {
          checkKeyIsUniform(key);
          NativeLight.setMat4(getNative(), key, x1, y1, z1, w1, x2, y2,
                              z2, w2, x3, y3, z3, w3, x4, y4, z4, w4);
      }
docs: Set the value for a floating point 4x4 matrix.
  @param key name of uniform to set.
  @see #getFloatVec(String)