I tried some hl2 maps and the need for speed most wanted map. I'm really impressed by how close the rendering is to the original games. Not only did they get the lighting and shading right, there are also details like the NPCs being present, or even animated falling leaves particles in the most wanted map.
I'm at a loss how they managed to convert/managed so many different formats — the textures, level data, sprites, etc. Rare games on the N64 made extensive use of "vertex shading" like techniques, and these have all been carried over to a higher degree than I would've expected...
Off topic, but you're the guy who made the HN User Tag script! I recognise you since I have you tagged as "tag-legend". Still waiting for you to post your creation as a Show HN! ;)
Many of the contributions are others reversing and implementing a new game on top of the existing API, so the really labor-intensive per-game work is still spread out reasonably well.
A lot of games use similar or derived map formats (for instance, most Valve games). There’s a fair bit of game-specific tinkering to do, but you sometimes don’t have to reverse-engineer a new binary format from scratch…
They are definitely ripped from the game. More significantly, there's a lot of work on the rendering engine side of things to make all these different types of games with their different rendering techniques work on the browser.
