Abstract: Recently, in the area of non-photorealistic rendering, there has been a significant effort in digital painting research to simulate traditional painting styles and painting pigments. In particular, the simulation of painting tools is very important because this enables an intuitive painting experience for a user and generates rich painting effects. Many painting systems have been proposed using brushes, but less for other painting tools. As a result, there is still a limitation in the variety of painting effects that can be generated. In this paper, we propose a method to simulate painting using a painting knife, which is an important tool in oil painting. We model a painting knife and model the pigments such that the system is suitable for realizing the impasto style. We also present a technique for simulating the interaction between a painting knife and pigments on a canvas in real-time.