Visualization
Visualization in Open CASCADE Technology is based on the separation of modeling data you want to display and select, and on the graphical presentation of that data structure. For visualizing data structures, OCCT provides ready-to-use algorithms, which create graphic presentations from geometric models. These data structures may be used with the viewers supplied, and can be customized to take the specificity of your application into account. Displaying is managed through presentation services, and selection in its turn is managed through selection services. With these services, data structures and algorithms are provided to display objects of an application, and to support graphical selection of these objects. Application Interactive Services (AIS) are provided to manage displaying, detection and selection of graphical presentations. These services associate data structures and interactive objects.
Please, refer for more details to Visualization User's guide See also: our web site at E-learning and Training. |
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3D Graphics (Graphic3d package) supports three-dimensional manipulation of graphic primitives such as polylines, planar polygons with or without holes, text, and markers by controlling attributes such as color, transparency, reflection, line type, line width, and text font. These primitives can be displayed, zoomed, panned and rotated in a 3D viewer, which runs using OpenGL graphic library on all platforms.
Most types of primitives supported by Graphic3d can be dumped to a vector file format such as PDF and PostScript. Export to vector formats is implemented with help of GL2PS library.
This library provides services for:
Selection of 3D data structures
Presentation of 3D data structures
Access to 3D presentation and selection is provided through AIS (Application Interactive Services). This package is a high-level interface that offers access to the lower-level presentation and selection services. AIS expand this underlying functionality with standard 3D selection attributes, presentation management, and standard 3D presentation attributes, and manages it in the definition of GUI viewers. To implement these services, AIS package includes the following:
Interactive context
Interactive objects
A graphic attributes manager
Selection filters
Interactive context pilots 3D visualizations and selections. The interactive context allows you to manage, in a transparent way, graphic and "selectable" behavior of interactive objects which is not yet defined in the predefined types of these objects.
AIS have two operating context types. The default neutral point type allows you to easily visualize and select entire interactive objects, which have been loaded into the context. Opening a local context allows you to prepare and use a temporary selection environment to select a part of an interactive object.
Entities which are visualized and selected in the AIS viewer are objects. They connect the underlying reference geometry of a model to its graphic representation in AIS. You can use predefined OCCT classes of standard interactive objects for which all necessary functions have already been programmed, or, in case you are an advanced user, you can implement your own classes of interactive objects.
Graphic attributes manager, or AIS Drawer, stores graphic attributes for specific interactive objects and for interactive objects controlled by interactive context.
Initially, all drawer attributes are filled out with the predefined values which will define the default 3D object appearance.
When an interactive object is visualized, the required graphic attributes are first taken from its own drawer if one exists, or from the context drawer if no specific drawer for that type of object exists.
An important aspect in selection is the filtering of entities you to select. Selection filters allow you to refine the dynamic detection context, which you want to put into effect. Some of these filters can be used at the Neutral Point, others in an open local context only. You can also program your own filters and load them into the context.