IR faster wihout embree ?

[Alexandre Besson]

In my case, my IR is faster (x10 in beginning) without embree (BVH full SAH).

Is this normal behavior?

(Last daily build win10 64bit max16)

[maru]

No, it's not normal. Disabling Embree should make IR (and regular rendering) super slow compared to Embree enabled.
Can you do a quick video recording showing what's going on?

[Alexandre Besson]

First IR with BVH full SAH)
Second IR with Embree

[Ryuu]

OK, so the actual rendering is faster with Embree, but the initial geometry preprocessing takes longer, right?

This is expected as the non-embree version is not really that optimized, which also results in faster preprocessing time (since it does not try to build the acceleration structures in optimal way). embree does more magic at the preprocessing stage to be able to render much faster. You can see the difference in the ray/s, where the non-embree version gets 6.2M, while embree scores 8.5M

IIRC we're already disabling some optimizations in embree to get faster preprocessing time in interactive, but we can probably look into it to find out if there's something more we can do.

[Ondra]

embree should actually have super-fast initialization, much faster than corona trees, especially for bigger scenes... we should investigate this

[Ryuu]

Alexandre, could you please send us the scene to check this issue? You can use the private uploader from my signature.

[Dung (Ivan)]

Hi Alexandre,

I investigated the issue using our internal scenes. My results are less surprising as they show either marginal difference or Embree being much faster then BVH full SAH.

No Embree:

Archiviz:
 - Scene Parsing: 00:00:46.786 - geo: 00:00:39.030
 - Scene Parsing: 00:00:45.157 - geo: 00:00:39.910
 
 Academy Exterior:
 - Scene Parsing: 00:00:04.781 - geo: 00:00:07.830
 - Scene Parsing: 00:00:04.615 - geo: 00:00:07.980
 - Scene Parsing: 00:00:04.751 - geo: 00:00:07.931
 
 - Scene Parsing: 00:00:04.876 - geo: 00:00:07.844
 - Scene Parsing: 00:00:04.799 - geo: 00:00:07.835

Embree:

Archiviz:
 - Scene Parsing: 00:00:46.720 - geo: 00:00:08.72
 - Scene Parsing: 00:00:44.410 - geo: 00:00:08.382
 
Academy Exterior:
 - Scene Parsing: 00:00:04.762 - geo: 00:00:01.789
 - Scene Parsing: 00:00:04.687 - geo: 00:00:01.795
 - Scene Parsing: 00:00:04.646 - geo: 00:00:01.896
 
 - Scene Parsing: 00:00:04.781 - geo: 00:00:01.701
 - Scene Parsing: 00:00:04.785 - geo: 00:00:01.772

Would it likely that your scene contains something that might be slowing down Embree. Would you be so kind and able to share your scene? (as Ryuu has asked) :)

[Ondra]

this is probably because embree has faster IR mode, while BVH SAH does not, so it parses exactly like in offline rendering. This is probably the same bug as "low mem being too slow" and "IR being too slow compared to offline rendering"