Adding Portals To Quake

For those who have played Quake extensively, adding portals seems unnecessary, as teleporters are already a core part of the game mechanics. What [Matthew Earl] accomplishes is more of the Portal style of portal by rendering what is on the other side of the portal with a seamless teleportation transition.

Of course, Quake is an old game with a software renderer. Just throwing another camera into the scene, rendering to another texture, and then mapping that texture to the scene isn’t an option. Quake uses an edge rasterizer and generates spans along scanlines that track where edges intersect the current scanline. Rather than making expensive per-pixel comparisons, [Matt] stashes the portal spans and renders them in a second render, so even with multiple portals, only a single screen’s worth of pixels are rendered.

However, this technique has no near clipping plane, which means objects can appear in the portal that don’t make any sense as they are in front of the portal’s viewpoint. Luckily, Quake has an ingenious method for polygon occlusion: the BSP. While [Matt] is manually checking polygons, the BSP is the perfect tool for bisecting a room along a plane. It’s an incredible hack, and we’re excited to see Quake expand into a puzzle game. [Matt] dives into greater detail on how the software renderer works in another video that’s well worth a watch.

Perhaps the most incredible aspect of this technique is that it could run on original hardware. If you want to bring a little more Quake to life, why not get the Quake light flicker in your house? Video after the break.

14 thoughts on “Adding Portals To Quake

  1. So… it’s replicating what GoldSrc engine had since 1998. There’s a reason why Valve is one of the biggest gaming companies and ID faded into obscurity eh?

    1. I state this confidently, but willing to be corrected: There is no feature in the base GoldSrc engine which allows a player to look through a portal. That feature didn’t show up until Portal 1 in the Source engine.

  2. that’s an abomination, anyone wanting to add portal to quake1 other than for the technical aspect and for learning has never played quake1… how would you telefrag other players with that? this might look nice but it’s breaking a major feature…

  3. The original Quake has GL support, so it’s not locked to just software rendering.

    Quake 3 Arena introduced ‘portals’ where you could see the other side and shoot weapons through them as part of the gameplay mechanic.

          1. And valve actually hired the team who did narbacular drop which had similar concepts as portal… Valve made a marvelous game but actually bought rather than created the concept…

  4. Incredible the sorts of places trolls hang out^^^^

    This sounds like an incredible thing for Quake.

    The game lives on in so many ways.
    Imagine if the trolls and naysayers had their way…
    The old game would have been done for even before the fist mission pack.

    Adding things to the original Quake, or making new games from the old engine is the way to go.

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