1 / 15

Octree Traversal

Octree Traversal. Ref: Revelles et al. 2000. Ray Tracing. Global illumination that considers shadow, reflection, refractions, …. The most time-consuming operations in ray tracing. Object-Ray Intersection. Octree. Hierarchical spatial structure that speeds up the computation.

ash
Download Presentation

Octree Traversal

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Octree Traversal Ref: Revelles et al. 2000

  2. Ray Tracing • Global illumination that considers shadow, reflection, refractions, …

  3. The most time-consuming operations in ray tracing Object-Ray Intersection

  4. Octree • Hierarchical spatial structure that speeds up the computation

  5. the process of finding the subset of voxels in an octree pierced by a directed line Only ray trace the objects in the voxels Two groups of algorithms Bottom-up: traversing starts at first terminal node intersected by ray. Use neighbor-finding to obtain the next node Top-down: start from the root node; recursive down to the terminal voxel Octree Traversal

  6. Ex: SMART[91] A bottom-up traversal

  7. Top-down Algorithm [Revelles00] In the following discussion, assume dx > 0 dy > 0 p d

  8. Ray/Boundary Intersection ty1 tx1 ty0 tx0

  9. Ray/SubnodeBoundary Intersection o2 o3 tx1 tym txm o0 o1 With these, the intersection parameters at child node can be easily derived tx0 Similarly,

  10. ty1 t and tx1  t0 ty0 tx0 Ray-Node Intersection (1) Parametrically,

  11. t and  t0 Ray-Node Intersection (2) ty1 ty0 tx1 tx0

  12. Equivalently tx1 tx0 ty0 ty1 tx1 tx0 ty0 ty1

  13. q2 q3 q0 q1 Algorithm If ray hit this node … Use tx0, tx1, ty0, ty1 to compute txm, tym This procedure selects the first-hit subnode

  14. Observation

  15. Summary • The method is based on parametric representation of the ray • Incrementally compute the parameter values at which the ray intersects the planes • Computation uses only additions and divisions by two

More Related