Abstract In this paper we present an efficient technique for sketch-based 3D modeling using automatically extracted image features. Creating a 3D model often requires a drawing of irregular shapes composed of curved lines as a starting point but it is difficult to hand-draw such lines without introducing awkward bumps and edges along the lines. We propose an automatic alignment of a user's hand-drawn sketch lines to the contour lines of an image, facilitating a considerable level of ease with which the user can carelessly continue sketching while the system intelligently snaps the sketch lines to a background image contour, no longer requiring the strenuous effort and stress of trying to make a perfect line during the modeling task. This interactive technique seamlessly combines the efficiency and perception of the human user with the accuracy of computational power, applied to the domain of 3D modeling where the utmost precision of on-screen drawing has been one of the hurdles of the task hitherto considered a job requiring a highly skilled and careful manipulation by the user. We provide several examples to demonstrate the accuracy and efficiency of the method with which complex shapes were achieved easily and quickly in the interactive outline drawing task. Highlights We present an efficient technique for sketch-based 3D modeling using automatically extracted image features. An automatic and real-time method is proposed to align a user's hand-drawn sketch line to the contour lines of an image, facilitating a considerable level of ease for 3D modeling. We use a geometric method to align a sketch line to the outlines of an image using the features of the sketch line and contour lines of an image, and some operations are proposed to refine the result of alignment. In the sketch-based 3D modeling method, the sketch line is represented by a editable spline, therefore, the aligned sketch line can be further adjusted interactively.