1. A method for simulating physical effects in two-dimensional (2D) drawings, comprising: receiving input specifying a two-dimensional (2D) physical simulation tool to be applied to a 2D object in a displayed digital image; receiving gesture input indicating a gesture that applies the specified 2D physical simulation tool to at least one point on the 2D object as indicated by the gesture input; in response to the gesture input, applying a 2D physical simulator corresponding to the specified 2D physical simulation tool to the 2D object, wherein the 2D physical simulator iteratively executes to apply a physics-based simulation to the 2D object as indicated by the gesture to generate a simulated physical effect; rendering results of said applying the 2D physical simulator to the 2D object in the displayed image; and generating an output image including the rendered results of said applying the 2D physical simulator to the 2D object.