Q3View_StartBoundingBox (IM: QD3D)

Inside Macintosh: 3D Graphics Programming With QuickDraw 3D /

Chapter 13 - View Objects / View Objects Reference

View Objects Routines / Bounding in a View

Q3View_StartBoundingBox
You can use the Q3View_StartBoundingBox function to start computing an object's bounding box.
TQ3Status Q3View_StartBoundingBox (
TQ3ViewObject view, 
TQ3ComputeBounds computeBounds);
view
A view.
computeBounds
A constant that specifies how the bounding box should be computed. See the following description for details.

DESCRIPTION
The Q3View_StartBoundingBox function begins the process of calculating a bounding box in the view specified by the view parameter. After calling Q3View_StartBoundingBox, you specify the model (for instance, by calling Q3Geometry_Submit). When you have completely specified that model, you should call Q3View_EndBoundingBox to complete the bounding operation. The renderer attached to the specified view might need to reprocess the model data, so you should always call Q3View_StartBoundingBox and Q3View_EndBoundingBox in a bounding loop.
The computeBounds parameter determines the algorithm that QuickDraw 3D uses to calculate the bounding box. You should set computeBounds to one of these constants:
typedef enum TQ3ComputeBounds {
   kQ3ComputeBoundsExact,
   kQ3ComputeBoundsApproximate
} TQ3ComputeBounds;
If you set computeBounds to kQ3ComputeBoundsExact, the vertices of the geometric object are transformed into world space, and then the world space bounding box is computed from the transformed vertices. This method of calculating a bounding box produces the most precise bounding box but is slower than using the kQ3ComputeBoundsApproximate method.
If you set computeBounds to kQ3ComputeBoundsApproximate, a local bounding box is computed from the vertices of the geometric object, and then that bounding box is transformed into world space. The transformed bounding box is returned as the approximate bounding box of the geometric object. This method of calculating a bounding box is faster than using the kQ3ComputeBoundsExact method but produces a bounding box that might be larger than that computed by the exact method.