basics: utilise the Knife
In our continuing series of CGI basics we look at using the knife tool
Tips for using the knife tool
I existing geometry or has the ability to slice through everything due to a creative decision.
Alas not all implementations of a cutting tool are the same. Some applications give more options than others, most will enable free-form cutting along the face of a model, but only a few offer viewport-based cutting.
Some cutting tools offer the ability to create gaps when slicing; this can be really useful for all kinds of modelling tasks, especially when the software can cap the open cuts. This is because in most 3D applications meshes are seen as shells rather than being solid; there are some applications that can see meshes as solid, but you’ll find that they f you’re new to CGI you may feel that there are far too many tools to choose from in a dizzying array of software. This series aims to break everything in CGI down to the very basics, so that every artist can be armed with the knowledge of which tool is best. This time we are looking at the knife function.
It goes by many names: knife, slice or cut to name but a few, but effectively the implementation is the same – it cuts through polygons and edges to either split objects up or to create new boundaries within a mesh from which to create new geometry.
A good slicing tool should enable an artist to cut either in a way that is sympathetic to the are usually limited to CAD and sculpting applications.
Some applications offer the ability to create curved slices, which is useful for creating organic shapes, and if the application has the ability to place images in the viewport as a guide, using a curved knife tool is a great way to match reference.
Even if the slice tool does not offer a curved tool, using a slice or knife tool on a single polygon can be great way to start a model.
The other area where a cutting tool can be useful is in defining polygon flow on meshes that are going to be animated, as well as for making sure that n-gons are divided into quads or triangles for model export.