This is a special builder type which is allowed to orient nodes to
strands direction, hence minimizing their surface area in comparison
with axis-aligned nodes. Such nodes are much more efficient for hair
rendering.
Implementation of BVH builder is based on Embree, and generally idea
there is to calculate axis-aligned SAH and oriented SAH and if SAH
of oriented node is smaller than axis-aligned SAH we create unaligned
node.
We store both aligned and unaligned nodes in the same tree (which
seems to be different from what Embree is doing) so we don't have
any any extra calculations needed to set up hair ray for BVH
traversal, hence avoiding any possible negative effect of this new
BVH nodes type.
This new builder is currently not in use, still need to make BVH
traversal code aware of unaligned nodes.
This was only visible on systems with lots of threads and root of the issue
was that we've been pre-allocating too much memory for all the threads.
Now we only pre-allocate data for the main thread and rest of the threads
does allocation on-demand.
This brings down memory usage from 36Gig to 6.9Gig when building spatial
split for the Bunny.blend file on our Intel beast.
Originally regression was happened by the threaded spacial split builder
commit.
The title actually covers it all, This commit exploits all the work
being done in previous changes to make it possible to build spatial
splits in threads.
Works quite nicely, but has a downside of some extra memory usage.
In practice it doesn't seem to be a huge problem and that we can
always look into later if it becomes a real showstopper.
In practice it shows some nice speedup:
- BMW27 scene takes 3 now (used to be 4)
- Agent shot takes 5 sec (used to be 80)
Such non-linear speedup is most likely coming from much less amount
of heap re-allocations. A a downside, there's a bit of extra memory
used by BVH arrays. From the tests amount of extra memory is below
0.001% so far, so it's not that bad at all.
Reviewers: brecht, juicyfruit, dingto, lukasstockner97
Differential Revision: https://developer.blender.org/D1820
There are in fact some missing parts to it (Split BVH builder should
be creating bins from result of Object Split constructor).
Doable, but need to quickly fix issue for the studio here, easier to
revert for now.
This has following advantages:
- Localizes all the run-time storage into a single structure,
which could easily be extended further.
- Storage could be created per-thread, so once builder is
threaded we wouldn't have any conflicts between threads.
- Global nature of the storage avoids memory re-allocation
on the runtime, keeping builder as fast as possible.
Currently it's just API changes, which don't affect user at all.
Avoid memmove() happening on every insert of duplicated node to the references
list. Temporary pre-allocated vector is used for new references which is then
being inserted into actual array in one go later.
Gives around 4x speedup building spatially split BVH for the grass field in the
cassette player shot from Gooseberry.
This commit implements object reference node spatial split making it possible
to use spatial split for top-level BVH.
The code is not in use yet because enabling spatial split on top level BVH is
not coming for free and it needs to be investigated if it's worth in terms of
improved render times.
This way it's easy to add more reference types allowed for splitting to the
BVH reference split function without making this function too much big. This
way it's possible to experiment with such features as splitting object instance
references.
So far should not be any functional changes.
This inconsistency drove me totally crazy, it's really confusing
when it's inconsistent especially when you work on both Cycles and
Blender sides.
Shouldn;t cause merge PITA, it's whitespace changes only, Git should
be able to merge it nicely.
should be no functional changes yet. UV, tangent and intercept are now stored
as attributes, with the intention to add more like multiple uv's, vertex
colors, generated coordinates and motion vectors later.
Things got a bit messy due to having both triangle and curve data in the same
mesh data structure, which also gives us two sets of attributes. This will get
cleaned up when we split the mesh class.
Patch [#33445] - Experimental Cycles Hair Rendering (CPU only)
This patch allows hair data to be exported to cycles and introduces a new line segment primitive to render with.
The UI appears under the particle tab and there is a new hair info node available.
It is only available under the experimental feature set and for cpu rendering.
=== BVH build time optimizations ===
* BVH building was multithreaded. Not all building is multithreaded, packing
and the initial bounding/splitting is still single threaded, but recursive
splitting is, which was the main bottleneck.
* Object splitting now uses binning rather than sorting of all elements, using
code from the Embree raytracer from Intel.
http://software.intel.com/en-us/articles/embree-photo-realistic-ray-tracing-kernels/
* Other small changes to avoid allocations, pack memory more tightly, avoid
some unnecessary operations, ...
These optimizations do not work yet when Spatial Splits are enabled, for that
more work is needed. There's also other optimizations still needed, in
particular for the case of many low poly objects, the packing step and node
memory allocation.
BVH raytracing time should remain about the same, but BVH build time should be
significantly reduced, test here show speedup of about 5x to 10x on a dual core
and 5x to 25x on an 8-core machine, depending on the scene.
=== Threads ===
Centralized task scheduler for multithreading, which is basically the
CPU device threading code wrapped into something reusable.
Basic idea is that there is a single TaskScheduler that keeps a pool of threads,
one for each core. Other places in the code can then create a TaskPool that they
can drop Tasks in to be executed by the scheduler, and wait for them to complete
or cancel them early.
=== Normal ====
Added a Normal output to the texture coordinate node. This currently
gives the object space normal, which is the same under object animation.
In the future this might become a "generated" normal so it's also stable for
deforming objects, but for now it's already useful for non-deforming objects.
=== Render Layers ===
Per render layer Samples control, leaving it to 0 will use the common scene
setting.
Environment pass will now render environment even if film is set to transparent.
Exclude Layers" added. Scene layers (all object that influence the render,
directly or indirectly) are shared between all render layers. However sometimes
it's useful to leave out some object influence for a particular render layer.
That's what this option allows you to do.
=== Filter Glossy ===
When using a value higher than 0.0, this will blur glossy reflections after
blurry bounces, to reduce noise at the cost of accuracy. 1.0 is a good
starting value to tweak.
Some light paths have a low probability of being found while contributing much
light to the pixel. As a result these light paths will be found in some pixels
and not in others, causing fireflies. An example of such a difficult path might
be a small light that is causing a small specular highlight on a sharp glossy
material, which we are seeing through a rough glossy material. With path tracing
it is difficult to find the specular highlight, but if we increase the roughness
on the material the highlight gets bigger and softer, and so easier to find.
Often this blurring will be hardly noticeable, because we are seeing it through
a blurry material anyway, but there are also cases where this will lead to a
loss of detail in lighting.
