The visualization module of Analysis Situs is based on VTK (Visualization Toolkit) [Schroeder, 2006], which is a widely-used and industrially proven open-source library. Analysis Situs adds the CAD-oriented data processing pipelines to specialize the generic VTK engine for Computer-Aided Design use cases. The main contribution of Analysis Situs in this regard is adding a set of data sources that convert precise B-rep geometries to the polygonal format of VTK. In this chapter, we give an overview of the visualization techniques available in Analysis Situs.
By default, Analysis Situs comes up with a shaded display mode having edges rendering enabled.
The display mode of the active CAD part can be tuned in the Parameter Editor.
One important setting that is related to both visualization and interactive selection is the "Use scalars" flag. If disabled, the per-element colors are not rendered. Since the highlighting mechanism is also based on scalars, it will not show up as well. The following image illustrates the rendering view without scalars. As you can see, shape anomalies are not accented anymore with the red color.
To enable the visualization of the B-rep facets backing the precise geometry, press "W" ("wireframe") key whenever the focus is set to the viewer. The facets are rendered in hidden line removal mode, so you see only the visible features of a model. To get back to the shaded view, press "S" ("shading").
The "W"/"S" toggle is applied only to the actors that are currently visible on the scene. If you want to keep the visualization of facets enabled for a dedicated object while keeping others shaded, temporarily hide them from the scene and use the toggle.
Hidden line removal
Press "H" ("hidden") key to render the hidden line image of the active Part. The "Alt + H" combination is reserved for a discrete HLR which is designed to work faster at the expense of presicion loss.