Clipping visualized 3D models with user-defined clipping planes is one of basic OpenGL features that allows the user to look inside the models.
However, in some cases it is more interesting to investigate the cross-section shape rather than the model's internals. For this purpose, the cross-section should be visualized in shading using some distinctive visual attributes (specific color, hatching).
Solving this task geometrically might be a heavy work with large complicated CAD models. If visualization of the cross-section is the only goal, this task can be solved efficiently using OpenGL-based capping algorithm.
Currently, the capping algorithm is being implemented in the OCCT visualization component. Capping will be applicable on per-object basis. Visual attributes for cross-section will be defined at the level or individual clip planes. An important consequence of this improvement is that clipping planes in general will be applicable to both the whole 3D view and individual 3D presentations. Capping is optional property of the improved clipping plane API.
It should be noted that OCCT interactive selection will be also improved to take object-specific clipping planes into account, to avoid interactive selection of the object parts that were clipped. The current development results can be obtained from OCCT Git branch CR24070_2.
A snapshot showing sample results of the capping algorithm (three object-specific clipping planes, different visual attributes used for each of the three sections):