It’s pretty hard to tell from this info but… Things to check:
-
Is the PP volume infinite / or is your camera inside it?
-
Things could well look different if the main block of cubes is placed in the level and the others are spawned in. Can you just spawn the lot?
-
What kind of lighting do you have anyway? - I think that’s the most critical thing
-
Are these all the same type of cube?