Firearm CTH display can be misleading

[ToxiClay]

Describe the bug

While standing on a roof and aiming at an enemy right next to the building, 100% CTH is displayed, but no shot connects.

Steps To Reproduce

1. Load attached save.
2. Invoke fire menu.
3. Observe listed 100% chance to hit.
4. Take the shot.
5. Observe no result.

Expected behavior

I expected to blow the enemy to kingdom come.

Screenshots

Versions and configuration

• OS: Windows
  • OS Version: 10.0 20H2 (build 19042.685)
• Game Version: 0.E-8388-gb85c4a9 [64-bit]
• Graphics Version: Tiles
• Game Language: System language [English]
• Mods loaded:
  • Dark Days Ahead [dda],
  • C.R.I.T Expansion Mod [crt_expansion],
  • No Fungal Monsters [No_Fungi],
  • Disable NPC Needs [no_npc_food],
  • Alternative Map Key [alt_map_key],
  • SpeedyDex [speedydex],
  • Stats Through Kills [stats_through_kills],
  • Stats Through Skills [StatsThroughSkills]

Additional context

Woodcock.zip

[PaulBlay]

Yeah, you're shooting through the roof there. Sometimes it will show your line of fire going through the corner of a wall. What does the CTH display show then?

[int-ua]

AFAIU path taken by the projectile not always matches the line perfectly as there is always some spread in accuracy. Does it fail 100% of the time if you try shooting a lot of times?

[ToxiClay]

Yeah, it failed 100% of the time.

[Salty-Panda]

A sidenote:
The same happens while throwing grenades/casting spells at something below & one tile away, to be exact
Projectiles hit the tile you're on
Maybe the function to project line to target goes
X_________________X______XX
XX, instead of_____X, or___X
One could possibly check this by using spell/attack that ignores walls/surfaces?

EDIT. Yes, Gravity Well ( "NO_PROJECTILE" flag ) works properly when cast at this range

[actual-nh]

One could possibly check this by using spell/attack that ignores walls/surfaces?

Try the Magus Magic Missile spell (has the NO_PROJECTILE flag). (It does need to be targeted at a hostile, not at the ground, BW.)

[Cyprex]

Without any z-level stuff you can sometimes to select targets that actually have a wall in the way.

[PaulBlay]

@Cyprex

Without any z-level stuff you can sometimes to select targets that actually have a wall in the way.

Yeah, I was going to say something like that. Then I actually tried firing (burst mode) at a target that supposedly had a corner wall in the way and it got shot up nicely. Which is what int-ua was talking about ...

AFAIU path taken by the projectile [does] not always matches the line perfectly as there is always some spread in accuracy.
Does it fail 100% of the time if you try shooting a lot of times?