Glide details...

Hi all, I'm currently building a demo that requires a few glides. All glides are through 32-unit gaps with parallel linedefs. I understand that movement speed needs to be very low to do this, but I could use a few examples as I haven't had any luck, yet. Can someone point me toward a few demos with this type of glide?

Are there specific conditions under which this is possible, or is it simply a matter of placement?

I've only done one such glide so far which you can find in this thread. Position is all important, just a matter of getting that absolutely perfect and then you go on through.

Not quite what I'm dealing with(no wall to run up against), but that's okay. While working on a DSDA update I ran across Xit's pn08-042 which is exactly my situation. From the looks of it, it depends more on being in just the right position(near the exact center) and less on movement speed(Xit got it with a GF37 tic, if I'm not mistaken).

Now, the hard part: duplicating it. Man, this is frustrating.

Thanks! :-)

You might know this already, but be sure to disable novert (or the equivalent) to use the mouse to make precise movements.

dew did one in the pl2 demo thread I think. I think it was the p204-045.zip run. If you need to go slow and precise maybe keyboarders can't do this.

my glide is wall aligned, so i didnt have to mouse strafe to find the right spot. and i used keyboard for finding the right angle, it's somehow easier when recording :)

Xit's pn08-042

I missed this one - I've just been inspired to do 19 seconds but can't upload so will attach.

Here's my method of doing the glide:

1) Use vanilla Doom (nosound is OK here), be recording, set mouse sensitivity to the lowest, don't disable vertical movement, adjust your monitor so it shows the entire picture.

2) Run towards the gap and keep on running - you will slide against the wall. Turn straight until you no longer seem to be sliding - this is easier while recording as angles are "chunkier".

3) Slowly mouse-strafe until you are almost precisely aligned with the gap.

4) Run against the wall - you will slide very slowly left. This is how you move precisely into position. You can tell the position is right immediately the first column of pixels of the front face of the left wall comes into view (this is why you need to see the whole picture - the contrast is very clear on this map but it usually isn't so!).

5) Edge directly forward with the mouse as slowly as you can - just push hard enough for your gun to start trembling. With a bit of practice it should go rather easily on this map, but on others it's a lot harder and you may have to make repeated tries for minutes at a time for it to work.

That's for normal play, I don't know about building. I believe that slow forward movement is not important for getting through the gap, but rather for moving into position. Moving forwards slides you slowly to the left, so lots of GF1 ticks rather than a few GF50 ticks gives you many more chances of being in exactly the right position.

Thanks everyone.

You're right Cack, it is used to move into position. Best I can figure is that you have to be at the EXACT center between the two bars. When building, the DRE X/Y position readouts don't have enough precision(even at five decimal places) to tell you when you're there. My strategy was to get the readout to show you as being in the right position(center point, with five zeroes after it), then inch forward with GF1s. Once I figured this out, I was able to do it several times.

I was working on an MM28 Nightmare run, because I thought with an Arch-Vile jump and a glide you'd be able to access the Yellow Key. What I didn't know was that the door leading up to that can only be opened by a switch, which requires the Blue Key to access. A shortcut would still be possible, but it would require three Vile jumps instead of one(into/out of the Blue Key room, in addition to the ledge leading to the YK); plus one glide at the end. I don't know if I want to even try building that.:-)

This is really disappointing, because the thirty seconds I created is pretty cool. For your amusement, here's what I built before I realized I hadn't quite thought this through. Man, Jens was good.:-)

mm28nm_badshortcut_aro.zip

cack_handed said:
I've just been inspired to do 19 seconds but can't upload so will attach.

Sounds cool. And where is it?

Andy Olivera said:
three Vile jumps instead of one(into/out of the Blue Key room, in addition to the ledge leading to the YK)

You probably missed this.

Yes, I did miss that one. So it would take two Vile jumps. Still, that extra jump adds a considerable increase in difficulty...

Andy Olivera said:

Best I can figure is that you have to be at the EXACT center between the two bars.

Yes. Internally the engine uses coordinates which are in 16.16 fixed point. That is coordinates can be written in the form (xpos+xfrac/65536, ypos+yfrac/65536) for integers xpos, ypos, xfrac and yfrac, with xfrac and yfrac between 0 and 65535.

Now the wad format only stores the integer part of a vertex's coordinate. That means, in the above notation, all vertices have xfrac and yfrac equal to zero.

In order to glide, you have to be exactly lined up with these map vertex coordinates, having no fractional component to your position.

Incidentally the infamous second glide between the bars on scythe map18 is possible, but to do it I had to edit a savegame to put myself in exactly the right position. It seems to be impossible to walk there. Why some of these types of guideless glides[1] are possible, and others are not, is currently beyond me.

[1] "guideless" as opposed to those with walls you can hug to guide yourself into the right position - e.g. the first glide on scythe map18, which is almost trivial to accomplish.

RjY said:

In order to glide, you have to be exactly lined up with these map vertex coordinates, having no fractional component to your position.

Incidentally the infamous second glide between the bars on scythe map18 is possible, but to do it I had to edit a savegame to put myself in exactly the right position. It seems to be impossible to walk there. Why some of these types of guideless glides[1] are possible, and others are not, is currently beyond me.

I tried that glide and found it to be not very hard, so I suppose it all depends on your setup. For me it's almost impossible to do them at all with prboom and have to revert to using Vanilla. One thing worth noting is that it's a lot easier to glide from east to west than any other direction.

Trying to attach a zip of sc18o016 & the missing pn08-019 ...

pn08sc18.zip

If there's anyone who likes to keep track of what glides are possible, I remember squeezing through a ring of bars around a BFG and cells in the first level of this and then I couldn't get out again. This is not especially relevant to this thread, but I wanted to share.