Invisible Walls Defined: Invisible walls are triangles without corresponding textures. They're implemented in the game to prevent players from accessing unintended areas or to guide gameplay by funneling players along specific paths.
Surface Triangles and Hitboxes: The game uses surface triangles for floors, walls, and ceilings, each with hitboxes extending in specific ways. For floors, the hitbox extends downward, allowing Mario to "snap" onto the floor. Wall hitboxes project outward to repel Mario, and ceiling hitboxes extend both below and infinitely above, affecting Mario's movement differently depending on his actions and position.
Out-of-Bounds and Ceiling Mechanisms: If Mario is in the air or water, he can move into out-of-bounds areas, leading to game termination scenarios. Ceilings prevent upward motion past a certain point and are programmed to extend indefinitely upwards, though practical effects are mostly near the actual ceiling.
Interaction with Invisible Walls: These walls can result from ceiling hitboxes not contained by floors (leading to "exposed ceiling hitboxes"), misaligned vertices creating gaps, or walls slightly leaning forward, allowing out-of-bounds elements to intrude into playable space. Players notice these most when they unexpectedly bonk into them, disrupting movement or trajectory.
Analyzing Invisible Walls: To analyze and identify invisible walls, the video suggests looking at how triangles are paired into rectangles and checking how these geometries align on the grid. Misalignments due to integer-based vertex storage can create unexpected interactions like gaps or overlaps in expected collision boundaries.
Game Design and Invisible Walls: The video explains that many invisible walls were intentionally placed to enhance the gameplay experience, prevent exploits, or manage game performance by restricting access to complex or non-essential areas.
