Update usage.md

docs/src/usage.md

@@ -36,3 +36,31 @@ println("Best design found: ", result)
 
 **Returns:** 
 - The best design `x` found by DIRECT.
+
+
+The package also provides `direct`, which is the same as `optimize` except it returns all hyperrectangular intervals:
+
+```julia
+using DividedRectangles
+
+# Define the objective function
+f(x) = x[1]^2 + x[2]^2 + 3 * sin(5 * x[1]) + 2 * cos(3 * x[2])  # Multivariate example
+
+# Set the search bounds
+a = [-2.0, -2.0]
+b = [2.0, 2.0]
+
+# Run DIRECT
+intervals = direct(f, a, b, max_iterations=10, min_radius=1e-4)
+
+```
+
+**Arguments:**
+- `f`: The objective function to be minimized.
+- `a`: Vector of lower bounds for the search space.
+- `b`: Vector of upper bounds for the search space.
+- `max_iterations`: (Optional) The maximum number of iterations (default: 100).
+- `min_radius`: (Optional) The minimum radius of hyper-rectangles (default: 1e-5).
+
+**Returns:** 
+- All hyperrectangular intervals maintained by DIRECT.