Use noskip textures on a func_wall instead 

sorry, I meant skip textures 

Because not using skip textures.. possible makes some surfaces disappear when looking from different angles? 

I placed armor and health on elevator (func_train) which slowly goes from up to down.. when it reaches its destination bottom, I hear stopping sound and then items falls through floor..

Should I use skip there as well? I already tried clip brushes. 

Right now in my map I'm trying to create a little plant in a pot, like one of those shitty plastic ones you see in foyers or something like that. Does anyone have any advice on the best way to go about it? I'd be happy to just have a texture that's feasible to cut a shape out of with brushes, I've got some good ideas as to how to use something like that, but something better would be nice as well.

It's an AD map so although I haven't looked into it I think I can load arbitrary models, so that's another avenue.

What would be really juicy is a guide on how to get transparent textues working in Q1, if that's even possible (I doubt it!). I've got a .wad with a plant that I could use if this was made possible somehow, but it's on that ugly pink background and the details are far too fine for me to simply chop it out, even at the smallest possible grid size. 

Several AD maps use fence textures (vines in ad_swampy, broken windows in ad_necrokeep) so you could try that - add a "{" to the beginning of the texture name so it's something like "{plant", this will make palette index 255 transparent.

It's not a vanilla quake feature but engine support is good (QS, MarkV, FTE, latest DP) 

Skip = the compiler removes the textures from the visual plane, so there are invisible but solid surfaces the monsters can walk over like they was a smooth floor. It's preferable to make them func_wall, because then you can cover the whole gap. They can work as world geometry as well - however, then they can't touch adjacent geometry as that would cause their faces to become invisible as well.

Skip works in vanilla Quake which makes it the way to go, whereas alpha is only supported by a handful of ports. 

An apparent exception to the "can't touch adjacent geometry" rule seems to be if the brushes that are skipped are func_illusionary brushes. Obviously not applicable for creating invisible solids, but still an interesting exception. I'm using it to make a "catwalk" for my map: http://i.imgur.com/M5o1Dsa.jpg
http://i.imgur.com/WUpcCxs.jpg

Also, is the "monsters can't walk on clip brushes" statement actually true? I ask because this guy seems to be doing just fine, granted this is in a mod, not the default game. 

monsters use pointcontents in order to avoid walking off cliffs. this means that they'll refuse to walk over gaps,
the exception is if they're already off the side of a cliff, in which case they're 'allowed' to just walk off it entirely, thus there's no issue if they spawn on it, but they won't step back onto the clip brush if they did find solid ground.
obviously you can trick the movetogoal function by adding in FL_PARTIALGROUND before each call to it, but you'd probably need extra triggers for that... 

I have a spot where monsters not walking on clip brushes is less than good. I've been avoiding anything not part of Quake originally, but would this "alpha" thing work on a moving entity like a door?

If so, is it done in the engine or by the compiler? 

a func_wall with only skip textures on it will be totally invisible (and not do nasty things to pvs+csg+etc), and yet still support monsters walking over it just fine.

however, your shots will also hit it instead of passing straight through, which is how come monsters will be willing to walk over it.
so pick your poison. 

The walkway is made of four bars. At first they are not extended. Later they move to the position here (lower right).

http://quaketastic.com/files/screen_shots/Wish13_e.jpg

Sorry for the poor angle, but the screenshot is one I uploaded a while back.

Monsters do not move on to the walkway because of the gaps. I've used monsters that have ranged attacks, but it would be better if they would use the walkway once it extends. A func_wall or skip textured brush won't work because of the need to move. 

Would making a second overlapping func_door that's just a skip-textured box work? 

Skip textures work on doors? That was what I was asking. I didn't know, never use them.

Special compiler needed? I use txqbsp_xt

I was thinking to try the tyrutils as long as marksurfaces don't go up, but I would have to relight a lot of the map because there are parts that look a lot different from MH/BJ light. I think it's the lack of "soft distance". 

There is already a clip brush inside the bars to smooth out the "bumpiness" to the player, changing that to a separate door would be no problem. 

I'm pretty sure skip on doors will work fine with txqbsp-xt or tyrutils (I tested my version, probably the original works too). As spike said it'll block gunshots but otherwise it should be ideal. 

Does it really need to be func_wall only, when using skip textures? Just wondering because func_train is used in many places, and if ever decide make a floor about irons bars then there will be problems if monsters can't move over it. 

In general, for anything non moving I would use a func_wall. For something that moves along one axis only, func_door. If a complex path is needed, multiple directions, continuous loop, etc., that is what func_train is for. I don't actually use func_plat any more, too limited. 

By the way.. because I'm still discovering new keys and things... does func_door has key "angles" like in buttons? 

Yes, but like buttons, only in the horizontal plane, and from what I've seen it can get confusing if you use non-orthogonal directions.

Doors make great lifts and extending walk ways, you just have to learn how to control them by setting the "lip" value. 

So it is better than func_plat in many cases?

I tried using now skip, I think I asked about whether it makes same effect when using invisible textures.. and it makes the same weird effect, it kind of don't want to draw some faces:
https://drive.google.com/file/d/0BwxYkKdSD855eDdtQU1JdEpPSE0/view?usp=sharing 

From Quake Wiki...

"Skip is a nonstandard special texture, used by modern QBSP compilers, but does not have any function in the stock Quake compilers as released by ID Software. Skip is a texture much like clip in that it is invisible, but skip's use is to remove an entire face from ever rendering, and a brush does not have to be fully textured in skip. The removed face remains solid, and will block player and monster movement, as well as block weapon fire. In general, this is of little use on solid geometery, as Quake performs backside culling, but can be used on brush entities or "hacks" like windows to hide unwanted faces. A "*waterskip" texture exists as well, for use with liquid brushes."

So you use it only on those faces of a brush that you want to remove, not on a whole brush. 

I don't want to remove anything, I only want to let monsters move surfaces. 

Thanks for who mentioned about func_wall + alpha.. it worked! 

Looking at your screenshot I think you have a grid, and that you want monsters to be able to cross the grid?

If so, then you cannot cover the whole grid with one skip brush. You need to fill each of the spaces in the grid with a brush of exactly the same size as the gap, and with the same texture as the grid, then retexture just the top and bottom faces of that new brush with the skip texture.

After compiling, the faces with the skip texture will be solid but invisible, meaning that you can see what is below the grid, and all the other faces of that brush will remain, thereby making the grid look complete. Monsters will then be able to cross the grid.

I used that technique in FMB-BDG2 where I had a grid with some holes big enough for the player to fall through if he was not careful, and skip textures everywhere else so that the monster could chase the player across the grid and maybe panic the player into falling through one of the bigger holes (those bigger holes did not have skip textures in them).