Add the math3d.move_towards function

README.md

@@ -151,6 +151,7 @@ The table briefly describes the included helper math functions. The source code
 | `math3d.lerp(t, a, b, [dt])` | Linearly interpolates between `a` and `b` by `t`. The parameter `t` is clamped to the range `[0, 1]`. | `Mathf.Lerp` |
 | `math3d.lerp_angle(t, a, b, [dt])` | Same as `vmath.lerp` but makes sure the values interpolate correctly when they wrap around 360 degrees. | `Mathf.LerpAngle` |
 | `math3d.limited_lerp(t, a, b, max_step)` | Same as `vmath.lerp` but `max_step` limits the increment of value. | - |
+| `math3d.move_towards(a, b, max_delta)` | Moves the `a` value towards `b`. | `Mathf.MoveTowards` |
 | `math3d.ping_pong(t, length)` | Pingpongs the value t, so that it is never larger than length and never smaller than 0. | `Mathf.PingPong` |
 | `math3d.repeat_(t, length)` | Loops the value t, so that it is never larger than length and never smaller than 0. | `Mathf.Repeat` |
 | `math3d.sign(x)` | Returns the sign of x. | `Mathf.Sign` |

scene3d/helpers/math3d.lua

@@ -191,9 +191,9 @@ function M.lerp_angle(t, a, b, dt)
 end
 
 --- Calculates the lerp parameter between of two values.
+-- @param t Value between start and end.
 -- @param a Start value.
 -- @param b End value.
--- @param t Value between start and end.
 -- @return A percentage of value between start and end.
 function M.inverse_lerp(t, a, b)
     if a ~= b then
@@ -203,6 +203,18 @@ function M.inverse_lerp(t, a, b)
     end
 end
 
+--- Moves the `a` value towards `b`.
+-- @param a Current value.
+-- @param b Target value.
+-- @param max_delta A maximum change that should be applied to the value.
+-- @return An interpolated value.
+function M.move_towards(a, b, max_delta)
+    if math.abs(b - a) <= max_delta then
+        return b
+    end
+    return a + M.sign(b - a) * max_delta
+end
+
 --- Pingpongs the value t, so that it is never larger than length and never smaller than 0.
 function M.ping_pong(t, length)
     t = M.repeat_(t, length * 2)