Some players use external tools that inject code into the running game process.
Unlike texture packs, this mod did not rely on opacity. It manipulated the render distance and block culling via core tweaks: minecraft 152 xray work
The "Redstone Update" (1.5.2) introduced a bizarre physics exploit that required zero mods and zero texture packs—only a piston and a lever. Some players use external tools that inject code
Because TNT has a lit fuse animation and pistons have moving tile entities, spamming the lever caused the render engine to "queue" more visual tasks than it could handle. The engine would prioritize entity animation over solid block rendering. For a split second, all solid blocks would fail to load, but ore blocks (which are not entities) would remain visible. Because TNT has a lit fuse animation and
Note: This did not work on servers with anti-lag plugins, but on a vanilla 1.5.2 survival server, it was a devastatingly easy exploit.