The aim of this paper is to analyse the emergence of spatial–semiotic resources attached to an eighth-grade student's use of 3D modelling software while solving certain spatial tasks. The data comes from a task-based interview and it is analysed within a spatial-semiotic lens, including different kinds of resources not only based on the discourse, but also based on extra-linguistic expressions such as that sketches and gestures. The results of the study show that generally the student's reasoning steps explored a viewpoint for adding or removing cubes by use of the ‘orbit' and ‘select' tools, using ready-made mental pictures derived from completed steps, linking 2D and 3D representations through spatial visualisation and spatial orientation, emergence of spatial vocabulary including his strategies and generalizations.