Renderer efficiency question

[Creaphis]

Before I get in trouble with a map I'm working on I figure I'd better ask this. I'm making a huge area with a whole mess of lines. There generally shouldn't be more than a few hundred lines visible at once - the rest of the lines in this area will just have lower textures, and will be blocked from view by raised floors. Here's the question: will these unseen lines slow down the rendering process for either software or hardware renderers? I'd assume that they still undergo some line-of-sight calculations, and I don't want to bring anyone's computer to a crawl with no visible reason.

For that matter, what's the "new" rendering limit? How many lines can be visible at once before the hypothetical average computer will suffer a significant drop in framerate?

[esselfortium]

I'm pretty sure that unless there's either a 1-sided line or a touching floor/ceiling (i.e. a completely solid 2-sided line), Doom will keep processing all the lines behind it, and they'll add to the drawsegs count for that frame, as it has to step through all of the lines to see whether it needs to do anything with them.

Visplanes, on the other hand, should only be rendered if they're actually visible.

Someone more knowledgeable can correct me if I'm wrong.

[Chopkinsca]

From experience, I noticed that 1 sided lines lowers the number of lines rendered. Phocas2 map01 has a "wall" of 1 sided line cliffs to lower the rendering lag.

Could be wrong though.

[Graf Zahl]

I can only speak for hardware rendering.

Any hardware renderer has to render all parts of a two-sided line if some part of the line is in line of sight. One could add additional checks but they tend to be very expensive. It's easier to pass the polygons to the graphics hardware and let it sort it out.

[Creaphis]

Alright, thanks everybody.

So, if these hidden lines do take some extra processing power, how many extra lines would it take to slow worse-to-average computers down to uncomfortable framerates?

The answer isn't crucial now, I've already changed my layout to prevent problems of this sort, but I'm still curious.

[Graf Zahl]

Creaphis said:

Alright, thanks everybody.

So, if these hidden lines do take some extra processing power, how many extra lines would it take to slow worse-to-average computers down to uncomfortable framerates?

That depends on so many things that it is hard to tell. And the things that cause slowdowns are quite different for hardware and software rendering.

[Creaphis]

Fair enough.