Graphics Reference
In-Depth Information
Ray Segments
- - - - ææææææææ - - - - >
- - ææææ - - - - ææææ - - >
----ææ---- ææ---->
--
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--
æææææææææææææ - - >
Figure 10.6.
CSG ray tracing.
left subtree of the CSG tree for an object
X
, then it will also miss
X
except possibly
in the case where the operation at the root is the union operation.
The CombineSegs function in Algorithm 10.2.3.1 described in [Roth82] consists
of three steps:
(1) One merges the sorted endpoints of the segments in LL and RL to produce a
new segmentation of the ray.
(2) The resulting segments are classified as “in” or “out” depending on the set
operation being applied to the left and right subtree of the CSG tree and the
classification of the segments in LL and RL.
(3) Lastly, contiguous segments with the same classification are merged to sim-
plify the result.
Step (2) uses the following lookup table:
