Melee attacks sometimes having a bigger range than intended

[Ahli]

In some cases, melee units seem to be able to attack over a much greater distance than expected.

• A Zealot kills an SCV that constructs a Supply Depot in a wall: https://www.twitch.tv/uthermalsc2/clip/AttractiveGracefulLyrebirdPeteZaroll

• A SCV kills a Probe across a Pylon and Vespene Geyser: https://clips.twitch.tv/TangentialAdorableOpossumHumbleLife-Us0E1TsqAa1FY9ou

Facts:

• Workers and Zealots have a weapon range of 0.1 and a range slop of 1.0
• Zealots have a damage point of 0.0. Workers have 0.167
• You can see the units rotating when they acquire the other unit. When they finish rotating they are likely starting the weapon execution
• Inner radius of workers is 0.375. Radius is 0.375
• Inner radius of Zealot is 0.375. Radius is 0.5
• units usually overlap slightly with their radius (maybe due to math precision issues)
• Both of above cases have the attacker damage a building before. This could be a part of the issue
• Both units were in walled off areas (would be weird if that had anything to do with this)

Weapon range visualized: The difference is day and night!

Theories:

• the weapon could skip its initial range check for some reason, then the slop is in range
• distance calculation is boken in general?
• distance calculation is broken around structures?
• distance calculation is broken towards terrain that the attacker cannot reach (footprints)?

[Ahli]

I was able to recreate the first bug in an automated test map.

Test Map - the bug with happen at 1:10 on timer

Test results:

• happens with melee flag disabled
• happens with arc 360
• happens with range 0.0
• happens with random delay min 0.0
• happens with damage point 0.01
• happens with continuous scan enabled
• happens with only fire at attack target disabled
• range slob 0 fixes this. The Zealot sometimes moves/rotates oddly as it briefly acquired the SCV, but it is not able to damage beyond its weapon range. There seems to be a rounding error in the trigger script, so the max valid range in the trigger script needs to be 0.1033 instead of 0.1
• Zergling has the same issue
• happens to Marines (with weapon range 0.1) as well

[Ahli]

It does not happen when I set the range slop to 0. => This is a fix for the Zealot. His second hit is not influenced by the weapon, so this is a fix without side effects.

However, the bug is still present for all other melee attackers =/

When I reduce the range slop, it only happens at that distance. So, the buggy scenario uses the range slop distance to initiate an attack. For the Zealot, range slop 0.1 and range 0.0 do not trigger the bug. Having both at 0.1 triggers it. Thus, the buggy scenario uses both ranges combined when starting an attack

Partial Fix:

Most units with a damage point of 0.0 can have their range slop set to 0.0. Just the Mutalisk could require that value as it has to slow down, thus I would not suggest changing it without a lot of tests. The following units can be altered without issues:

    <CWeaponLegacy id="InterceptorLaunch">
        <RangeSlop value="0"/>
    </CWeaponLegacy>
    <CWeaponLegacy id="LurkerMP">
        <RangeSlop value="0"/>
    </CWeaponLegacy>
    <CWeaponLegacy id="MothershipBeam">
        <RangeSlop value="0"/>
    </CWeaponLegacy>
    <CWeaponLegacy id="P38ScytheGuassPistol">
        <RangeSlop value="0"/>
    </CWeaponLegacy>
    <CWeaponLegacy id="PsiBlades">
        <RangeSlop value="0"/>
    </CWeaponLegacy>
    <CWeaponLegacy id="PunisherGrenades">
        <RangeSlop value="0"/>
    </CWeaponLegacy>
    <CWeaponLegacy id="VolatileBurst">
        <RangeSlop value="0"/>
    </CWeaponLegacy>
    <CWeaponLegacy id="VolatileBurstBuilding">
        <RangeSlop value="0"/>
    </CWeaponLegacy>