The rocks that are giving off the black blotches are separate figures. They are actually asteroid props from a space set I have, re textured to match the landscape prop. But even with the textures that were default I was getting this. The main reason for them is to cover the cave entrance, as it is a square object not meant for distance shots.So the surrounding environment is one prop, the cave another prop and the rocks with the black spots 4 individual figures placed to cover the empty parts of the cave prop.