[hypertele-Xii]

> It had portals before Portal.

Not entirely accurate. Narbacular Drop, the first prototype for Portal (that caught Valve's attention and they hired the devs to recreate the tech in Source engine) was released a year before Prey, in 2005.

[oblak]

I actually deleted the line I had written about Narbacular Drop. You're technically correct, which is the best kind of correct, of course, but Prey was stuck in a development hell for what, 10 years? It had portals in the 90s!

[jasonwatkinspdx]

Portal Rendering style engines were invented in the early 90s. I think several people had roughly the same idea at the same time in academia, as well as industry.

Descent was based on a portal and cell renderer that used a unit cube with limited orientations as the cell. This let them simplify and pre tabulate some of the rendering math.

The PVS precalculation done for quake levels is effectively a portal renderer.

Unreal's software renderer needed portal rendering to limit overdraw, so the engine was based around it.

[hypertele-Xii]

Those portals are baked into the maps. I think we're specifically discussing dynamic portals, where the player has the ability to bridge any two spaces at runtime.

Descent can't do that.

[jasonwatkinspdx]

The way the underlying engine works is what's significant, not that it's a dynamic game design element. Descent levels are just a graph of cubes where a portal rendering algorithm runs per cube instance in a flood fill that spreads from the camera origin until there's no more unclipped portals visible on the screen. You could totally make a portal gun mechanic in that engine, they just didn't want to. Well beyond the hatches that open and close, which do case an end to the portal rendering cell walk when closed.

There's nothing particularly novel about Portal (the game) style portals in rendering. Racing simulators did the exact same thing for rear view mirrors for decades prior. It's just another transform in the scene graph clipped to a subscreen area.

[hypertele-Xii]

We are still not talking about rendering. Rendering portals is trivial, and as you say, is the basis of nearly all 3D engines as a means to figure out what to draw. But that info is compiled as the visibility graph into the game map data structure and cannot be modified in realtime.

Narbacular Drop is like, literally the first 3D game ever released that allowed dynamic creation of portals at runtime.

[jasonwatkinspdx]

I am aware of what you're saying. Please reread what I wrote a bit more carefully and charitably. Dynamic portals are not a precedent worth talking about.

[jamesfinlayson]

I think I remember an old game CD having screenshots of Prey from the 1990s - in .pcx format no less!