anchor.diff:     gl_Position = uProjectionMat * vPosition;
   
      vTexcoords = aTexcoords;
  -   vNormal = uNormalMat * aNormal;
  +   vNormal = normalize(uNormalMat * aNormal);
   }
   """;
   
  
positive.code: uniform mat4 uModelMat;
  uniform mat4 uProjectionMat;
  uniform mat4 uJointMat[$MAX_JOINTS_PER_MESH];
  
  varying vec4 vPosition;
  varying vec2 vTexcoords;
  
negative.code:   gl_Position = uProjectionMat * vPosition;
  
    mat3 normalMat = getNormalMat(modelViewMat);
    vec3 normal = normalize(normalMat * aNormal);
  
    highp vec3 ambientLight = vec3(0.6, 0.6, 0.6);
    highp vec3 directionalLightColor = vec3(0.5, 0.5, 0.75);
  