IBM Visualization Data Explorer Programmer's Reference

Chapter 16. Rendering

Partial Table-of-Contents

This chapter describes the Data Explorer rendering model, introduces additional elements of the data model relevant only to rendering, and describes routines for manipulating data structures for rendering. (For descriptions of these routines, see Appendix C. "Data Explorer Library Routines".)

The Data Explorer renderer is designed for data visualization. For example, it directly renders scenes described by the Data Explorer data model (see Chapter 3. "Understanding the Data Model"). The renderer handles all combinations of Groups and Fields as input Objects. The members of a Group or of a subclass of a Group (e.g., Series and Composite Fields) are combined into one image by the renderer.

Rendering a scene involves fours steps:

1. Transformation to world coordinates--Applying transforms specified by transform nodes in the Object.

2. Shading--Assigning colors to the vertices, using the intrinsic surface colors, surface normals, surface properties specified by Field components, and lights specified by Light Objects.

3. Transformation to image coordinates--Applying transforms specified by a camera Object.

4. Tiling--Generating an image by interpolating point colors and opacities across faces, and rendering volumes with a rendering algorithm.

16.1 Transformation

Transformation is the process of computing pixel coordinates from model coordinates (i.e., the coordinates of the Object). Because DXRender() performs necessary transformations, most applications do not need DXTransform() .

Transformation is essentially a two-step operation: (1) transform the model coordinates of an Object into world coordinates; and (2) transform the world coordinates into image coordinates (see Figure 10).

Figure 10. Transformation of Coordinates
The transformation from model to world coordinates is specified by transform nodes (see 16.4 , "Xform Class") in the description of the input Object. The transformation from world coordinates to image coordinates is specified by a camera Object.

Object DXApplyTransform()

Recursively applies a transform to an Object. See DXApplyTransform.

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