Explosions

Explosive Damage to Walls and Objects

Explosive damage to objects (anything that isn't a unit) is constant; grenades will always form the same blast pattern on the same terrain. The peak damage is done at the center and falls off by 10 points per tile radius.

It's known that a 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 discussion, NKF/Jasonred/Zombie, strategycore forums 2005 -JellyfishGreen 02:21, 25 Aug 2005 (PDT)

Blast Propagation

Blaster Bombs impart damage as follows:

 Distance From
  Ground Zero Damage Range
        0      100 - 300
        1       90 - 290
        2       80 - 280
        3       70 - 270
        4       60 - 260
        5       50 - 250
        6       40 - 240
        7       30 - 230
        8       20 - 220
        9       10 - 210
       10        0 - 200

Taken from a post by Zombie. Behavior past 10 tiles is not entirely certain.

Notice how 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.

Another way to view damage is relative to its edge (HPs=Health Point damage):

DFE   HE   MinHPs AveHPs  MaxHPs   N

 1   Gren     0     1.27     5    15
     AC-HE    0     2.50     8    10
     HC-HE    2     7.90    22    10
     SR       8    23.33    42    15
     LR      10    24.80    48    15
     BB      37    79.44   125    27

 2   Gren     1    11.60    20    15
     AC-HE    4    12.10    21    10
     HC-HE    7    21.10    37    10
     SR      12    33.60    57    15
     LR      15    36.60    60    15

 3   Gren     5    18.47    34    15
     SR      17    43.40    70    15
     LR      20    47.12    73    17

 4   LR      30    60.50    91    2

 5   LR      30    56.50    83    2

Where "DFE" equals Distance From Edge (1 is just inside edge of blast radius). The numbers are for Muton Soldiers (armor=10, max Health Points=125) not hit through their Under Armor, in Desert terrain.

Here we see that standard Grenades do very little damage at their edge, but Blaster Bombs are still doing tons and able to kill massive Mutons even there. (The edge for BBs was 13 tiles from GZ for the above.) The numbers also support the idea that BBs continue to decrease by 10; extending the Blast Propagation table to 13 gives 0-170; minus 10 for Muton armor leaves a max of 160; half of that (80) was seen, on average.

Zombie has posted a detailed discussion of the mathematics for blast propagation here.

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).

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.

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.

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).

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.

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
  50  65     Purple floor 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                                                    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  20     Normal ground. Death tile only needs 2 TUs!            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.

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 not a separate tile; they are objects. 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 this means, I don't know. Zombie, you listed wheat and corn fields in your Diameter table, but everything on the farm looks like wheat to me, and they all point to the same wheat object... ? Also, there are different types of dirt and grass. I assume you meant the common grass on the farm for your tests. I am taking a guess at what your terrain was for some of the columns... some of the descriptions are pretty succinct... probably the best thing is for you to use MapView to get them yourself. Please edit the Blast or Tile tables all you want.

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.

I tried my best with these values, but they can be awful hard to tell apart. I even broke out the magnifying glass under /Accessories /Accessibility! (Then, after I was done, I noticed that TopView clarifies just which tile is where, sigh.) Plus that was a lot of numbers to track. I did not methodically get all walls, and there are many (esp. small) objects that can be added to terrain and cause increases(?) in armor and possibly other values. Example: Rocks in the desert are separate objects, with 20 armor. So take these values as a rough guide. 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!).

Weirdness in the Mountains

Mountains have an inherent weird property in that some structures placed on them are "weaker", 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.

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. (Ramps otherwise are armor=255, i.e., indestructible.) 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 ground strength is less than 60.)

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).

Blaster Bomb Pattern

See Also

• Damage Formula
• Firing Accuracy
• Throwing Accuracy (including throwing distance)
• Reactions
• Weapons
• Health
• Fatal Wounds
• Armor