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  1. RAY TRACING: SPEEDING UP THINGS (OBJECTS)
  2. RAY TRACING: SPEEDING UP THINGS (GLOBALS)
  3. RAYTRACING: INDEX OF REFRACTION (IOR)
  4. RENDERING: FILTERS FOR STILL IMAGES VERSUS VIDEO
  5. RENDERING VIDEO: RENDER FRAMES, NOT FIELDS
  6. RENDERING VIDEO: MAKE SURE VIDEO COLOR CHECK IS ON
  7. RENDERING VIDEO: CHECK YOUR GAMMA!
  8. RENDERING GREAT BIG, GIANT, HONKING, ENORMOUS IMAGES SUCCESSFULLY
  9. DON'T RENDER MOVIES—RENDER FRAMES!
  10. SPEAKING OF THE RAM PLAYER...
  11. RERENDERING FROM THE ENVIRONMENT BACKGROUND
  12. OKAY, SO YOU REALLY WANT TO RERENDER YOUR ANIMATION...
  13. IFL = IMAGE FILE LIST
  14. YOU CAN'T CREATE .IFL FILES ON READ-ONLY MEDIA!
  15. MANIPULATING IMAGE SEQUENCES USING .IFLS
  16. CREATE NESTED .IFL FILES
  17. A CHICKEN AND EGG PROBLEM: HOW DO YOU SET UP AN ANIMATED BACKGROUND FOR A SCENE IF YOU HAVEN'T RENDERED THE BACKGROUND YET?
  18. COULD YOU MAKE THINGS MORE COMPLICATED, PLEASE? (WHAT ABOUT USING A COMPOSITING PROGRAM?)
  19. COMPOSITING USING VIDEO POST
  20. RENDERING WITH SCANLINE MOTION BLUR: MULTI-PASS AND IMAGE
  21. RENDERING WITH SCANLINE: MIX IMAGE AND MULTI-PASS MOTION BLUR
  22. RENDERING IMAGES FOR PRINT: TEACH THOSE PRINT FOLKS A LESSON (OR TWO...)
  23. RENDERING IMAGES FOR PRINT: OH YEAH, ANOTHER THING...
  24. "THOSE PRINT PEOPLE"—MAKE IT EASIER ON THEM WITH 3DS MAX 6
  25. THE PRINT SIZE WIZARD (ENOUGH WITH THE PRINTING STUFF ALREADY!)
  26. MENTAL RAY IS IN THE BUILDING!
  27. MENTAL RAY IS ON THE COUCH!
  28. USE MENTAL RAY'S IMAGE SAMPLING WISELY
  29. IN MENTAL RAY, CONTRAST CAN SAVE YOUR DAY!
  30. HIDDEN LINE RENDERING: RENDER TO VECTORS IN MENTAL RAY
  31. TRIM YOUR (BSP) TREE IN MENTAL RAY
  32. MENTAL RAY PREFERENCES: PLEASE LEAVE ME A MESSAGE
  33. RENDERING AESTHETICS: OUTER SPACE SCENES
  34. RENDERING AESTHETICS: UNDERWATER SCENES
  35. RENDERING AESTHETICS: DISTANT LANDSCAPES
  36. RENDERING AESTHETICS: STILL LIFE AND MACROPHOTOGRAPHY
  37. "HELLO... YOU'VE GOT RENDER!"
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This chapter is from the book

This chapter is from the book

TRIM YOUR (BSP) TREE IN MENTAL RAY

In mental ray's Rendering > Render > Renderer tab, look at the Rendering Algorithms section. Under Raytrace Acceleration: Method, there's a drop-down menu where the default is set to BSP. A BSP (binary space partition) "tree" basically is a method of categorizing your whole scene with the help of an imaginary sub-divided bounding box encompassing your scene. This is necessary because it helps mental ray cast rays much faster in this structure than without.

Figure 6.35Figure 6.35

The subdivision cells of this bounding box are called voxels, and the creation of those is what you control with the two settings Size and Depth. Size is the number of cells along one side, so the default would divide your whole scene into a maximum of 10 x 10 x 10 cells. Depth is the parameter that tells mental ray how many subdivisions of one cell should be allowed. The default of 40 allows a maximum of 40 subdivisions in voxels, with a lot of faces.

That's the theory. In practice, you're looking for a good balance between the creation of your BSP tree (the "idle" time before the actual render starts, when the grid is built and subdivided) and the render time of your image. Increased BSP values can cause a long scene render preparation time but result in a lightning-fast render; conversely, decreased settings result in the preparation/render time equation being reversed. The time difference might not be seconds; it might be much longer.

Depending on the complexity of your scene, pay attention to your BSP settings and experiment with different Size and Depth subdivision values. Due to the nature of the default "bounding box" effect, you might be better off tweaking these settings from scene to scene until you get the results you want (or at least, the results that you can live with).

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