Explosions
Explosive Damage to Walls and Objects
Explosions differ from weapons in a couple of important ways.
- First, of course, they are area effect. (Duh.)
- Second, they impart damage within a narrower range than weapons. Weapons impart from 0 to 2 times their rated strength. (In other words, the UFOpaedia is showing you their average strength.) But explosives have a minimum of average/2 and a maximum of 3/2*average. So a blaster (HE 200) does from 100 to 300 damage at ground zero (GZ). You will still receive the damage listed in the UFOpaedia at GZ, on average. But you are guaranteed to get some damage (if not so far from GZ that the minimum has become zero). Of course, if your armor is high enough relative to the damage roll, it will block any actual damage.
Average explosive damage to units decreases by 10 per tile away from GZ. At the same time, the maximum damage is decreasing by 15 (3/2*10) and the minimum damage by 5 (10/2). Thus at GZ of a grenade blast (HE 50), units receive 25-75 damage, and at its outer edge (radius=5 inc. GZ), units receive 5-15 damage.
Unlike for units, explosive damage to non-units (ground, walls, and objects) is constant. Thus a specific explosive will always form the exact same blast pattern on the same type of terrain. It is calculated based on the minimum damage (i.e., average/2) for a given square. Thus it starts (at GZ) as half average damage and decreases by 5 per tile outward. If this value is greater than tile armor strength, the tile will be destroyed. However, a given type of explosive always has the same blast radius, regardless of terrain effects (except if there is blockage by e.g. walls). A Blaster can still kill you when 11 tiles away, even if you're on hard UFO floors which will only be damaged four tiles from GZ.
HE Statistics
Here's a table of explosive strength and resulting expected blast damage and radii.
HE @ Ground Zero HE @ Edge Type Min Ave Max BD BR Disc Min Ave Max AC - HE 22 44 66 7 3 0 7 14 21 Grenade 25 50 75 9 4 0 5 10 15 HC - HE 26 52 78 7 3 1 11 22 33 Proxy 35 70 105 13 6 0 5 10 15 Small Rocket 37.5 75 112.5 9 4 2 17.5 35 52.5 Rocket Tank 42.5 85 127.5 11 5 2 17.5 35 52.5 Alien Grenade 45 90 135 13 6 2 15 30 45 Large Rocket 50 100 150 13 6 3 20 40 60 Hi - EX 55 110 165 13 6 4 25 50 75 Fusion Hovertank 70 140 210 23 11 2 15 30 45 Blaster Bomb 100 200 300 23 11 8 45 90 135
- HE @ Ground Zero is damage to units at ground zero (GZ). Min=Ave/2, Max=Ave*3/2.
- HE @ Edge is damage at the edge of the blast.
- BD is Blast Diameter (including GZ tile)
- BD is Blast Radius (not including GZ tile)
- Disc is the discrepancy between actual radius, and the radius expected based on HE. Higher explosives have their blast size 'nipped'. Otherwise the Blaster would have a diameter of 39 - almost 4 tilesets wide!
Average damage to units falls off by 10 per tile away from GZ. Damage to tiles is fixed at half the damage for that tile (i.e., the minimum damage that units can receive) and decreases by 5 per tile (half the 10, that the average is decreasing). Note that damage is still done to units at the stated radii, even if blast strength was not strong enough to damage tiles. That is, you can still be hurt even past where you see floor damage. This is especially true in UFOs and alien bases, which have very strong tiles (see Blast Diameters and Tile Characteristics). Even the mighty Blaster only hurts UFO floor tiles (armor=80) out to four tiles from GZ, but your men can still be killed 11 tiles away, regardless. Also note, floor damage does not "soak up" any of the blast. However, some tiles (especially wall tiles) have an "HE Block" value which does prevent some damage from being passed on. This is what keeps blasts from acting as if walls didn't exist.
Because damage to tiles is fixed, they always produce the same blast pattern for a given type of terrain. Terrains differ in their "armor" (a.k.a. constitution) levels, and are destroyed if the blast damage is equal to or greater than their armor. Most ground terrain also has a second "damaged" tile which appears when the first tile is destroyed. This second tile (a.k.a. death tile) may also be destroyed by the blast, if the blast strength is equal to the armor for both tiles. Raw earth is left if all tiles are destroyed. Some tile sets (such as arctic) have the second death tile set to such a high armor value (255) that no blast will destroy it; thus you'll never see raw earth right under the surface of ice(!). For what it's worth, you can calculate the tile armor simply by looking at the blast pattern and comparing the HE strength (dropping of by 5 at center) to the point where tiles are no longer damaged.
Example: On a desert map, a prox mine will make a pattern with damaged tiles out to a radius of 6. The 9 innermost tiles (radius=1) will show a different tile (blown to raw earth). The first tile in desert has armor of 5 (thus, it's damaged all the way to edge of blast) but the second "dimpled" tile seen after the first one is blown through, has armor of 25. The prox mine is HE 70, so it's hitting ground zero for 35 and GZ+1 for 30. Thus it blows through to raw earth out to GZ+1 (5+25=30).
You may also see additional terrain damage with subsequent explosions. Example: the humble grenade (HE 50) damages the first tile (armor=5) out to radius=5, but does not break through the second tile (armor=25) to raw earth. But a second grenade in the same place will break through the injured tile at GZ, because now that the top tile is gone, the second tile is exactly equal to half grenade strength, right where it exploded.
Blast Propagation
As an example of a progressing blast front, Blaster Bombs impart damage to units as follows:
Dist from GZ Unit Damage
Rad Diam Min Ave Max
0 1 100 200 300
1 3 95 190 285
2 5 90 180 270
3 7 85 170 255
4 9 80 160 240
5 11 75 150 225
6 13 70 140 210
7 15 65 130 195
8 17 60 120 180
9 19 55 110 165
10 21 50 100 150
11 23 45 90 135
Based on testing by Zombie.
So, the Blaster Bomb is rated at 200 HE damage, and does that - but on average at ground zero. Then the range decreases by 10 per tile away from GZ. Maximum damage decreases by 15 (3/2*average), and minimum damage by 5 (average/2).
Unlike damage to units, tile (i.e., terrain) damage is fixed, and is equal to the minimum damage at that radius (i.e., half the average).
Most large explosions are "nipped" as shown above; in theory the Blaster could've kept going for eight more tiles until it decreased to zero. (But the blast pattern would've been HUGE!, Diameter=39.) Some smaller explosions are not nipped, and decrease until they drop off to zero.
Blaster Bomb Pattern
A screencap showing Blaster damage. Just for the halibut.
Ground Zero Effect
Units at ground zero (center of blast) and the eight adjacent tiles (GZ+1; nine tiles in total) receive damage through their Under Armor. All others receive damage to the side facing ground zero (never Under Armor).
This is true regardless of whether using thrown items (grenades, Hi-Ex) or shot/launched explosives (AC-HE, HC-HE, Rockets, Blaster).
Susceptibility
Critters have the following susceptibility or resistance modifiers to explosive damage:
Silacoid 130% Sectopod 80% Zombie 80% Tanks 70% Cyberdisc 60%
So Silacoids are more susceptible, presumably because they are close to the ground.
Equipment Destruction
Equipment dropped on the ground is destroyed by blasts of the following magnitude. Blast magnitude is given as half the average for that tile, i.e., equipment is assumed to be treated like tile armor damage, not like unit damage. This is supported by the fact that damage never varies; it occurs as a fixed function of blast strength.
Min Damage Equipment Destroyed
5 Electroflares
10 Unloaded standard pistol ammo (that's all that's destroyed! past flares)
15 Everything* except the three plasma weapons and the blaster launcher.
Unloaded ammo for these four weapons is also destroyed.
20 (No change - the four weapons still survive)
25 Only plasma rifle and heavy plasma left
30 Nothing at all survives
* "Everything" includes all man-made, bought, and alien weapons, explosives, and ammo; medkits, motion scanners, everything I could think of. Rather than list it all, here's a pic.
Ammo loaded in a weapon is safe (until the weapon itself is gone).
Blast Diameters
Blast diameters differ according to terrain type. The table below was copied from a post by Zombie. To get radius, subtract 1 and divide by 2:
Grass,
Lawn,
Corn Dirt, Asphalt Polar
Fields,Weeds, Roads, White Snow,
Wheat Desert White Tin Tile Concrete Mars Mtn. Alien
Cost $/HE Weapon HE Fields Sand Shngls Roofs Roofs Walkway Sand Tundra Floors
700 15.9 AC - HE 44 7 7 5 3 1 1 0 0 0
300 6.0 Grenade 50 7 9 7 5 3 3 1 0 0
500 9.6 HC - HE 52 7 7 7 5 3 3 1 0 0
500 7.1 Prox G 70 11 13 11 9 7 7 5 0 0
600 8.0 Small R 75 9 9 9 9 7 7 5 0 0
6700+2E 74.4 Alien G 90 13 13 13 13 11 11 9 3 0
900 9.0 Large R 100 13 13 13 13 13 13 11 5 1
1500 13.6 Hi Ex. 110 13 13 13 13 13 13 13 7 3
8000+3E 40.0 Blaster 200 23 23 23 25 25 23 23 23 21
Tile Armor - Initial 6* 5? 10 20 10? 20 25-40 40 50
See next section Dead 50 255 255 255 30? 255 30-255 20 50
* "Wheat" is complex - see Note 3 under Tile Characteristics
Where HE is the High Exposive rating for each round and: "White Shingles" is the roof on the gas station complex, "Mars Sand" is the soil on the Martian surface in Cydonia, "Alien Floors" is the floor of an alien base (alien ships were not checked), and "Concrete Walkway" is sidewalks near buildings or roads. Buy price or manufacturing cost are also shown (part cost only; does not include labor), whether Elerium-115 is needed ("+E"), and "Dollars per HE" (Cost/HE).
Note that these diameters only show damage to terrain. Damage to units is still done out to the radius for each bomb, as shown in HE Statistics above. So you can still be killed by a Blaster if 11 tiles away in a UFO, even though the hard UFO floors are only damaged out to 4 tiles from GZ. The tiles do not "soak up" any damage AFAIK. (Not counting tiles with HE Block, such as walls.)
For an Excel spreadsheet with 2D diagrams of all blast patterns (including stun bomb and tanks), see this.
Terrain tile properties (Armor, HE Block, etc.) can be readily seen in DaiShiva's excellent MapView program.
Distance from Ground Zero
"Distance" from GZ for explosives is actually computed by taking the TUs needed to walk to tiles in the blast radius. For example, 2 diagonal tiles away is considered to be 3 tiles since it takes 6+6=12 TUs to walk (and 12/4=3). This can be modelled on a spreadsheet using the equation:
Distance = INT( MAX(X,Y) + MIN(X,Y)/2 ) where X and Y are positive offsets from Ground Zero
This simplified approach sometimes makes blasts a little stronger down diagonals than would be expected from the Pythagorean theorem (a^2=b^2+c^2; a=SQRT(a^2+b^2)). Using Pythagoras, a diagonal tile is 1.4 tiles away, but the game considers them 1 tile away (INT(SQRT(2)). The 1.4 would've led to 1/1.4=71% blast strength. This is the worst case; the TUs approach is much closer to Pythagoras on a percentage basis at greater diagonal distances.
Tile Characteristics
This section is mainly for folks doing research on explosion propagation. Values were gathered with DaiShiva's excellent MapView program. Caution: You must install the extensive MicroSoft .NET platform to use MapView; see DaiShiva's site.
Ini Ded HEB Type _ 80 50 Most UFO floors UFOs AND ALIEN BASES 100 NDT UFO roof 100 220 100 Outer UFO walls 80 50 80 Most inner UFO walls 100 50 100 Inner UFO security walls (See Note 1) 80 50 80 Most inner UFO doors 100 50 100 Inner UFO security doors 100 NDT Partial UFO floors and adjacent tiles along diagonals etc. 50 50 Base floors 150 50 Green start tiles 200 50 Red elevator tiles. Yellow rays add 200 armor. 50 65 Purple floor around 2x2 elevators, in entertainment room, etc. 90 100 Dark black base floor in gardens and around command center _ 25 255 Arctic ground ARCTIC 20 255 Road CITIES 8 255 Smooth grass 10 255 Grass patches and dirt 15 30 Gas station ceiling - 150 Flame 10 30 Gray store floor 15 30 Slate roof for buildings - 160 Flame 18 50 Gray warehouse floor - 155 Flame 15 30 Rough gray concrete store roof - 150 Flame 12 40 Pastel pink(?) indoor tile - 111 Flame 8 255 Flowers 6 50 Pink patterned carpet - Normal 20 Flame, DT 100 Flame _ 40 30 Sand. Crater objects add armor, HE Block, 4 TUs. CYDONIA 100 NDT Green Start tiles. All others as for alien bases. _ 5 25 Sand DESERT 5 255 Grass FARM 10 255 Dirt and cultivated fields 6 25 Wood floor - Flame 16 6 25 25 Hay loft ground floor - Normal 12 Flame, DT 25 Flame 10 255 Stable - Flame 10 30 35 Cobblestone floor - 160 Flame _ 10 30 Light green weeds add 8 armor, 25-30 Flame FOREST 8 30 Plants add armor and HEB; see Note 2 JUNGLE 40 NDT Normal ground. Also see Mountain Madness. MOUNTAIN 50 NDT 50 Solid mountain walls (full height) _ 15 80 Common pink(?) or gray floors, inc. Access Lift XCOM BASE 10 80 Lighter tile in center of some common floors 12 70 Blue floors 16 80 Hangar floor _ 255 NDT 0 Ramp object. See Note 4. XCOM CRAFT 255 NDT 0 Floor of craft
"Ini" is initial tile armor; "Ded" is tile armor for the next ("dead") tile that appears after the initial one is blown away. If no tile is indicated (DeathTile=0), NDT is put. This means that raw earth will appear when the tile is killed, on ground level (or nothing does if above that, such as with UFO roof). Nothing is strong enough to break through Death Tiles with armor 255. Thus you can't break through artic ice to reveal raw earth, which makes sense. Basically anything over 100 (half the blaster's damage) cannot be broken through; thus elevators and start tiles (except in Cydonia surface!) are safe from explosions.
HEB is the "HE Block" value in MapView. We can only guess exactly how that works, at this point. Currently I (MTR) theorize that it does not add to tile armor; i.e., you can break through an outer UFO wall because its armor is 100; the HE Block is irrelevant for that square (but does damp damage that might have passed on to subsequent tiles). Thus HE Block is the variable responsible for preventing explosions from passing through walls as if they didn't exist.
Note 1: The inner UFO walls with "crown molding" have higher armor, and can be considered "security walls". The whole third level of battleship is this, and it's also found around the control room in large UFOs. Also, the darker doors without the line down their center are also higher strength. These are also generally found in secure areas; the top of the battleship elevator is ringed by them. These strong doors are also found in a few interesting places such as the entrance to the "engine room" on the bottom floor of the Supply Ship (even though the walls there are not security walls).
Most solid floors etc. have no flame ("Flammable") value. Most plants and human buildings do. Some tiles look weird, but make sense when you think about it. For example, cobblestone in farms has a high flame value - but it's found as the first floor of wooden buildings. Also (Note 2:) Most largish plants (shrubs and larger) had HE Block values. The jungle, in particular, has many full trees with HE Block of 20. Don't ask me why the hay loft ground floor has HEB=25.
There are a number of small objects that add armor to a tile. Example: Rocks in the desert are separate objects, with 20 armor. But snakes and bones are just painted onto a common desert tile; they are not separate objects nor do they add anything to the tile properties. Generally, anything that adds TUs also adds armor and possibly HE Block and Flammability. Most objects (including walls) that block movement add armor and HE Block, as well.
Note 3 (from Blast Diameters): For what it's worth, the effects of e.g. wheat and flowers in the farm map are actually added to the base tile (and add TUs to it). They are separate objects in addition to the ground tile. The additional TU costs can be seen in MapView, such as 2 (i.e., +2) for wheat. They also have their own armor ratings. Thus the wheat itself has Initial Armor 6, DT Armor 50 (this one shows burnt crops), which then goes to another DT (dirt) of Armor 255. But the tile it's on has Initial Armor 10, then goes directly to the same final DT as wheat (Armor 255). What happens is that wheat tiles go directly to their DT if blast strength is 60+, or to burnt crops if 60 > strength >= 6.
Note 4: All ramp-section objects add 4 TUs to underlying terrain except the middle and top of Avenger's ramp only adds 2 TUs. I think Danial has pointed this out before. Also see Mountain Madness.
Take these values as a rough guide. Some were hard to tell apart. If you want to do research on a particular tile, please double-check MapView before spending a lot of time on it! - MTR
Experience Points
Any alien (not under mind control) caught in a blast radius will give experience points toward Firing Accuracy. So one blast can give many Firing experience points. It does not matter if the alien was not harmed (i.e., damage was blocked by armor); you still get experience points if they were in the blast radius. Mind controlled aliens are considered friendly and do not give experience points.
The Small Launcher's stun bomb also gives Firing experience. Again, even if aliens did not actually fall unconscious (or receive any stun at all). Stun bomb radius in desert terrain is 5, diameter 11.
If thrown, one Throwing Accuracy experience point will be given. Note that if no one throws it (it's dropped instead), your first soldier gets the experience (even if a tank or if dead!). Thrown objects are attributed to the last person to throw them, or default to your first soldier "slot". Your tanks always occupy the first slot(s) (but enemy tanks such as the cyberdisc do not occupy your first slot).
If you make a reaction shot with a projectile explosive, you will receive one Reactions experience point, even if many aliens were hit by the blast (giving you many Firing XPs). Technically, you were only reacting to the movement of one of the aliens.
To see how experience points translate into skill points (when combat ends), see here.
NOTE: The Proximity Grenade does NOT give Firing experience to the thrower. Instead, it gives Firing experience to the person that triggers it to explode. Keep this in mind because this tends to make it a poor choice, especially early in the game (SIGH!).
Playing With Fire
The Blaster Bomb is the only thing capable of blasting through a UFO outer hull (walls and roof). It does exactly 200 damage at the epicenter and only ever knocks out one tile.
When we boost the power of the humble High Explosive with a game editor we see the following:
- 190 for HE strength is not enough to bust a hull open.
- 200 is, but only one tile wide.
- 210 opens up a hole 3 tiles wide
- 220 opens up a hole 5 tiles wide.
For every 10 points of HE strength above 200, it adds 2 to the width of the hole.
- reposted from NKF/Jasonred/Zombie discussion, strategycore forums 2005 -JellyfishGreen
Keep in mind that damage to tiles (as opposed to units) is actually a fixed amount based on half the average damage, as discussed above. Outer UFO walls actually have armor of 100. When HE strength is hacked, it also changes the minimum damage being applied to walls.
Mile-High Madness
Mountains have the inherent weirdness that they "weaken" some structures, as pointed out by NKF, BombBloke, and others. For example, a Blaster explosion on the ground below an XCOM craft will destroy its ramp and landing struts, in mountain terrain. Ordinarily, these objects are indestructible (armor=255) for all three troop transports.
The reason for this unusual behavior is seen by using MapView. It seems that XCOM programmers accidentally pointed to an object instead of a tile for the death tile of mountain terrain. It looks like they pointed to MCD id 76 (a stump object) when they should've pointed to MCD id 77 (scorched mountain ground tile). Perhaps someone stuck in an extra tile without keeping an eye on the pointers. In any event, this object only has armor of 20. It is theorized that when mountain terrain is destroyed (armor=40), the stump object then erroneously replaces e.g. the craft ramp, and then the explosion is also enough to take out that object. Note that the code for explosions appears to process ground first and then process objects; this must be how the inadvertent stump object also gets destroyed. (Otherwise is should've been seen all along the outer edge of a blaster explosion, where the blaster's tile-damage strength is less than 60; see Blast Propagation.)
Conversely, if you shoot a weapon at mountain ground terrain, you will see the stump. This is presumably because shots are "directed" at ground alone and only destroy the ground tile, whereas explosions are checked against everything in a square (ground, two walls, and object, if any). You can even turn craft ramps and gear into stumps, if you try hard enough. Most shots will hit the ramp instead of ground, but eventually one will miss and hit the ground, turning the ramp into a stump!
Another oddity due to the incorrect tile is that mountain ground destroyed in an explosion will burn for one turn. Most common ground tiles have 0 Flammability and will not burn due to an explosion. Presumably mountain terrain burns a turn because the stump has Flammability=14. It must burn one turn as a "last gasp" as the stump gets exploded and destroyed.
See Also
- Damage Formula
- Firing Accuracy
- Throwing Accuracy (including throwing distance)
- Reactions
- Weapons
- Health
- Fatal Wounds
- Armor