I need to check if a block can be passed through, such as any liquid, grass, or vines. 

Edited June 2, 20232 yr by MrDiamondDog
solved

You can check whether BlockState#getCollisionShape has an empty VoxelShape.

This works, thank you!

if you when to check whether blocks are completely "empty" (in terms of collision), that's that.

maybe you want to allow for blocks that are mostly empty (various rails or ladders). getCollisionShape, as Ash said, gives you blocks shape. multiply xSize * ySize * zSize and you get the volume. if you compare that to (for example) 13% of the full block, rails and pressure plates will pass but slabs will not.