This workbench is used in the initial stages of product development. It enables you to import
various sketches and images created by the product stylists into CATIA. In this workbench,
you will first position and scale the image in 3D space, then use CATIA Freestyle workbench
to draw the geometry over the Sketches.
The CATIA Sketch Tracer workbench is part of the Shape Design group of workbenches.

There are two ways of creating an Immersive Sketch:
Creating an Immersive Sketch using
an existing image
In the Sketch Tracer workbench, you can import the pictures created by stylist or you
can a take snapshot of an existing CATIA component. This process of importing an
image is called as creating an Immersive Sketch. Immersive Sketch is the image of a
product  that is used in 3D environment for designing the product.
Creating an Immersive Sketch using existing
an assembly or a part

The images or sketches created by a Stylist can be imported into CATIA and used to define the
wireframe elements like points and curves in FreeStyle workbench. These wireframe elements
will be further used for designing the parts in other workbenches.
The CATIA Sketch Tracer workbench allows you to import images, which offers following
benefits:
The images can also be captured from an existing geometry. These images can then be
modified in any image editing application (e.g. Photo Shop)  and then updated in CATIA
environment. CATIA keeps link between original images and the product in which images are
imported.