Wall portals

[ZZYZX]

Plane portal in ZDoom is essentially a skybox with dynamic camera. Renders the same way. That much, I know.

[Graf Zahl]

So why does this glitch so much but skyboxes don't?

[Graf Zahl]

How hard will it be to make this also work in hardware GZDOOM?

Not much. It's just waiting to be merged.

[edward850]

So why does this glitch so much but skyboxes don't?

Because the skybox camera never moves. The trick is with ZDoom's old portal camera is it offsets the rendering point relative to the portal surface during the render cycle, but this means the point can also be placed behind walls that are otherwise outside the "logical" area. It's pretty much the exact same problem mirrors have.

[Tormentor667]

This is good news

For ZDoom in general: How far is this from being merged? I imagine a lot of useful situations where you currently have to go crazy with 3d floors, for example creating a building and adding the interior through a portal.

[Graf Zahl]

but this means the point can also be placed behind walls that are otherwise outside the "logical" area. It's pretty much the exact same problem mirrors have.

That one's solvable. I had to cope with the same issue in GZDoom as well and managed to work around it. The solution would theoretically be transferrable to ZDoom.
(In short, it simply marks all subsectors belonging to a portal and if one is encountered during BSP traversal, the corresponding range in the clipper is marked visible. But this requires precise bounding boxes and shapes so it can't be made to work without GL nodes.)

The bigger problem is the 'no upper/lower textures' thing that severely limits what can be done with portals - and of course the performance issue. And even if I'd try to solve it - I'd only do it for linedef-defined portals, the thing-defined portals have been abused so extensively that any attempt to optimize here would break the bigger hack portals lile Urban Brawl.


For mirrors the solution is even easier: Do a simple PointOnLineSide check for each bit of geometry and discard anything that lies behind the mirror. I think the portal branch already implements this.

[hfc2x]

For mirrors the solution is even easier: Do a simple PointOnLineSide check for each bit of geometry and discard anything that lies behind the mirror. I think the portal branch already implements this.

Correct me if I'm wrong, but didn't ZZYZX try this already? There was a problem with actors placed behind the portal/mirror line causing their sprites to not render properly iirc.

[Graf Zahl]

Didn't I say this?

[Tormentor667]

For ZDoom in general: How far is this from being merged?

Sorry for asking again, I am just curious

[Major Cooke]

Didn't I say this?

He actually asked if zzyzx tried it under the notion that it hadn't worked.

Sorry for asking again, I am just curious

From looking over the past page, sounds like it's (almost) ready.

[Tormentor667]

This would come at the perfectly right time. Is this working also fluid through flats and not only walls?

[ZZYZX]

For mirrors the solution is even easier: Do a simple PointOnLineSide check for each bit of geometry and discard anything that lies behind the mirror. I think the portal branch already implements this.

Correct me if I'm wrong, but didn't ZZYZX try this already? There was a problem with actors placed behind the portal/mirror line causing their sprites to not render properly iirc.

It's in fact three simple PointOnLineSide checks:

Only lines that lie between the two 2D view rays AND are in front of the portal are drawn. Simple PointOnLineSide was causing various troubles.

Also to implement my method for plane portals, one would just need to calculate point of the portal sector that's closest to the player, and make virtual splitting line that goes through that point and is perpendicular to the player. Then translate this line to actual skybox/portal sector and clip with that, just as if it was a portal line on the picture.

[Graf Zahl]

In GZDoom I let the clipper (and the hardware stencil) handle the view angle but added a PointOnLineSide check for the actual portal line to exclude the stuff in front of the mirror. I guess in the software renderer it may not be enough because it's lacking the stencil so a bit more work is needed.

[Major Cooke]

Another thing to consider:


(red line = portal line)

Projectiles and hitscan attacks may want to skip damaging actors that are poking out through walls with a solid backside, if they aren't already.

[Tormentor667]

Is there an explanation btw how to use the line special in this special build? I'd like to test a few things

*EDIT*
Found the first post, was hard to miss

Anyway, a different question: I guess the height of the portal wall is always the whole sector, is this correct? Is it possible to restrict it somehow? For example by setting only the lower or upper texture as a portal?

*EDIT2*
To be more precise, test this one and you will see what I mean and want to achive
https://dl.dropboxusercontent.com/u/546 ... t_t667.wad