message: throw if the user gives us an invalid color format
diff: @@ -59,6 +59,14 @@ namespace ospray {
  } else {
  colorFormat = colorData->type;
  }
  + if (colorFormat != OSP_FLOAT4 && colorFormat != OSP_FLOAT3
  + && colorFormat != OSP_FLOAT3A && colorFormat != OSP_UCHAR4)
  + {
  + throw std::runtime_error("#ospray:geometry/spheres: invalid "
  + "colorFormat specified! Must be one of: "
  + "OSP_FLOAT4, OSP_FLOAT3, OSP_FLOAT3A or "
  + "OSP_UCHAR4.");
  + }
  } else {
  colorFormat = OSP_UNKNOWN;
  }
  