Radius
Many skill descriptions (notably those for a Necromancer's Curses and a Paladin's Defensive and Offensive Auras) specify radius in yards. However, radius is specified in sub-tiles in the game code; each sub-tile is a 2/3 yard by 2/3 yard square (i.e. 2 feet by 2 feet). Below is a diagram displaying both sub-tiles and radius in yards:
The radius of many skills increases with skill level, but skills with an invariable radius have been labelled:
| Skill | Radius | ||||||
|---|---|---|---|---|---|---|---|
| Sub-tiles | Yards | ||||||
| Terror | 4 |
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| Decrepify | 6 |
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| Iron Maiden | 7 |
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| Attract | 9 |
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| Redemption | 16 |
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20 |
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| Cloak of Shadows | 30 |
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Cloak of Shadows isn't labelled since its radius encompasses almost the entire visible area, with the exception of a tiny portion in the top left and right corners.
Sub-tiles
Diablo II uses an isometric projection which divides the horizontal playing surface into rhomboid tiles, each of which is composed of 5 x 5 sub-tiles. Below is an image of an individual sub-tile, magnified so that you can see the individual pixels and how the sub-tiles fit together:
Visible Area
Since a sub-tile is a 2/3 yard by 2/3 yard square (2 feet by 2 feet), this means the hypotenuse of the right-angled triangles created by bisecting that square from opposite corners is the square root of 8 (2² + 2²) in feet i.e. approximately 2.83 feet. Horizontally this distance equals 32 pixels, but vertically this distance equals just 16 pixels, resulting in the following:
| Resolution | Visible Area | |
|---|---|---|
| Pixels | Yards | |
| 640 x 480 | 640 x 433 | 18.86 x 25.51 |
| 800 x 600 | 800 x 553 | 23.57 x 32.59 |
If it seems counter-intuitive that the vertical distance in yards should be greater than the horizontal distance (since it's fewer pixels in length), take another look at the diagrams above; as an example, the radius of Inner Sight, Slow Missiles and Conviction is within the top and bottom limits of the visible area, but extends beyond these limits to the left and right.