Araújo, BrunoJorge, JoaquimMarcos, Adérito and Mendonça, Ana and Leitão, Miguel and Costa, António and Jorge, Joaquim2021-10-142021-10-142021978-3-03868-163-2https://doi.org/10.2312/pt.20031421https://diglib.eg.org:443/handle/10.2312/pt20031421We present BlobMaker, a program for modelling surfaces using variational implicit surfaces. Our approach uses variational implicit surfaces as a geometrical representation for free-form shapes. We have implemented new modelling operations to support stroke (pen-based) input. To this end, we have built a complete modeller application using variational implicit surfaces. Users can create and manipulate shapes using sketches on a perspective or parallel view. The main operations are inflate, which creates 3D forms from a 2D stroke, merge, which creates a 3D shape from two blobs and oversketch, which allows users to redefine shapes using a single stroke to change their boundaries or to modify a surface by an implicit extrusion. We compare these techniques with those of other approaches published. Finally, we describe their implementation in BlobMaker. We have provided additional features such as copying, picking and dragging to offer a natural user interface suitable free-form modelling.Stroke based modelling applicationvariational implicit surfaces10.2312/pt.2003142117-26