I've been looking at the documentation on pegging from both the SRB2 and Doom World wikis. As a result, I'm becoming more and more entrenched in my position and convinced that I'm right about this new behavior being wrong.
Let me explain with references.
First off is how we're introduced to using lower unpegged in the first place.
srb2 wiki said:
The way to manipulate middle textures is as simple as checking or unchecking "Lower Unpegged". This is a very useful tool in making maps.
http://wiki.srb2.org/wiki/Lower_Unpegged
At the time this was written, Peg Midtexture did not exist. It didn't need too. But what this did was it told us that this was the easiest way to attach textures like GFZGRASS and the fences from Castle Eggman to the ground.
Next is what the doom wiki is telling us about pegging:
DOOM Wiki said:
Alignment of wall textures is a fairly complex subject. The way textures are aligned depends on the type of line (single or two sided line), the linedef flags controlling pegging, and the sidedef offsets.
- If a linedef is one sided (a solid wall), the texture is "pegged" to the top of the wall. That is to say, the top of the texture is at the ceiling. The texture continues downward to the floor.
- If the "lower unpegged" flag is set on the linedef, the texture is instead "pegged" to the bottom of the wall. That is, the bottom of the texture is located at the floor. The texture is drawn upwards from here. This is commonly used in the jambs in doors; because Doom's engine treats each door as a "rising ceiling", a doorjamb pegged to the top of the wall would "rise up" with the door.
- The alignment of the texture can be adjusted using the sidedef X and Y alignment controls. This is applied after the logic controlling pegging.
What is failed to be mentioned here is that solid walls, or single sided linedefs, use only the midtexture and neither the upper or lower textures.
But due to SRB2's Max speed, we normally can't uses these linedefs as sonic can just thok right through them into the void of endless mass.
This means we have to use double sided linedefs, or thok barriers. Let's see what the doom wiki has to say about these.
DOOM wiki said:
- If a linedef is two sided, acting as a "bridge" between two sectors - such as a window or a step - the upper texture is pegged to the lowest ceiling, and the lower texture is pegged to the highest floor. That is, the bottom of the upper texture will be at the lowest ceiling and drawn upwards, and the top of the lower texture will be at the highest floor and drawn downwards. This is appropriate for textures that "belong" to the surface behind them, such as lifts or platforms.
This is the normal double sided linedef. so I won't bother explaining it.
DOOM wiki said:
- If the "upper unpegged" flag is set on the linedef, the upper texture will begin at the higher ceiling and be drawn downwards.
- If the "lower unpegged" flag is set on the linedef, the lower texture will be drawn as if it began at the higher ceiling and continued downwards. So if the higher ceiling is at 96 and the higher floor is at 64, a lower unpegged texture will start 32 pixels from its top edge and draw downwards from the higher floor.
- Both forms of unpegging cause textures to be drawn the same way as if they were on a one-sided wall — relative to the ceiling — but with the middle section "cut out". Unpegging is thus appropriate for textures that "belong" to the surface in front of them, such as windows or recessed switches.
- The alignment of textures can be adjusted with the sidedef X and Y alignment control. This is applied after the logic controlling pegging and affects all textures.
- If a middle texture is set, it is clipped by the highest floor and the lowest ceiling and follows the same alignment logic as for a single sided linedef, but does not repeat vertically.
http://doomwiki.org/wiki/Texture_alignment
Here's what the SRB2 wiki says
srb2 wiki said:
Most linedefs are two-sided, which means they constitute a border between two sectors. Which textures are rendered and how they are rendered depends on the height differences between the ceilings and floors of the two sectors:
The upper texture is drawn as a solid wall between the two ceilings. By default, it attaches to the lower ceiling and is drawn from the bottom up. If the Upper Unpegged flag is checked, it attaches to the higher ceiling instead and is drawn from the top down.
This is confirmed to be the same still
srb2 wiki said:
The lower texture is drawn as a solid wall between the two floors. By default, it attaches to the higher floor and is drawn from the top down. If the Lower Unpegged flag is checked, it attaches to the lower floor instead and is drawn from the bottom up.
Now this, this where SRB2 is making an error. Earlier this year, the Doom Community finally corrected the wrong info on their wiki to what is now quoted from them above. All source ports and Vanilla Doom Based games have all been using lower unpegged the way it is now documented before it was ever corrected.
Now according to a change log on the DOOM wiki, this description of lower unpegging that SRB2 is now following, was completely wrong.
http://doomwiki.org/w/index.php?title=Texture_alignment&diff=110918&oldid=95552
I don't know why SRB2 would go with a wrong description, but as I've been experiencing, peg midtexture is not really a good replacement.
There is one last line from the Doom wiki's page that I think needs to be quoted:
DOOM wiki said:
Level designers must ensure that textures tile in a consistent and aesthetically pleasing manner, such that the player is unaware that walls, floors and so forth are actually made of repeating textures rather than a single, continuous texture.
The new behavior of Lower Unpegged makes tring to do this that much harder.
