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This reverts commit ecbfa31caaadb03c53c0fe1459718b99613c8804.
Original commit broke logic in nodes re-fitting. That area can
access non-existing children momentarely. Not sure what would
be best solution here, for now simply reverting the change/
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The idea here is to make assert failure to fail sooner on an incorrect
node address rather than later with stack overflow.
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The issue was caused by some false-positive empty non-AABB intersection.
Tried to tweak it a bit so it does not record intersection anymore.
Hopefully will work for all platforms. Tested here on iMac and Debian.
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For proper indexing to work we need to use unaligned node with
identity transform instead of aligned nodes when doing refit.
To be backported to 2.78 release.
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Was causing CUDA issues on viewport edits.
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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.
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This seems to be straightforward way to support heterogeneous nodes
in the same tree.
There is some penalty related on 4gig limit of the address space now,
but here's are the thing:
Traversal code was already using ints to store final offset, so
there can't be regressions really.
This is a required commit to make it possible to encode both aligned
and unaligned nodes in the same array. Also, in the future we can use
this to get rid of __leaf_nodes array (which is a bit tricky to do since
trickery in pack_instances().
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There are several internal changes for this:
First idea is to make __tri_verts to behave similar to __tri_storage,
meaning, __tri_verts array now contains all vertices of all triangles
instead of just mesh vertices. This saves some lookup when reading
triangle coordinates in functions like triangle_normal().
In order to make it efficient needed to store global triangle offset
somewhere. So no __tri_vindex.w contains a global triangle index which
can be used to read triangle vertices.
Additionally, the order of vertices in that array is aligned with
primitives from BVH. This is needed to keep cache as much coherent as
possible for BVH traversal. This causes some extra tricks needed to
fill the array in and deal with True Displacement but those trickery
is fully required to prevent noticeable slowdown.
Next idea was to use this __tri_verts instead of __tri_storage in
intersection code. Unfortunately, this is quite tricky to do without
noticeable speed loss. Mainly this loss is caused by extra lookup
happening to access vertex coordinate.
Fortunately, tricks here and there (i,e, some types changes to avoid
casts which are not really coming for free) reduces those losses to
an acceptable level. So now they are within couple of percent only,
On a positive site we've achieved:
- Few percent of memory save with triangle-only scenes. Actual save
in this case is close to size of all vertices.
On a more fine-subdivided scenes this benefit might become more
obvious.
- Huge memory save of hairy scenes. For example, on koro.blend
there is about 20% memory save. Similar figure for bunny.blend.
This memory save was the main goal of this commit to move forward
with Hair BVH which required more memory per BVH node. So while
this sounds exciting, this memory optimization will become invisible
by upcoming Hair BVH work.
But again on a positive side, we can add an option to NOT use Hair
BVH and then we'll have same-ish render times as we've got currently
but will have this 20% memory benefit on hairy scenes.
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It was initially unsupported because initial idea of checking visibility
of all children was slowing scenes down a lot. Now the idea has changed
and we only perform visibility check of current node. This avoids huge
slowdown (from tests here it seems to be withing 1-2%, but more tests
would never hurt) and gives nice speedup of ray traversal for complex
scenes which utilized ray visibility.
Here's timing of koro.blend:
Without visibility check With visibility check
Original file 4min 20sec 4min 23sec
Camera rays only 1min 43 sec 55sec
Unfortunately, this doesn't come for free and requires extra data in
BVH node, which increases memory usage of BVH nodes by 15%. This we
can solve with some future trickery of avoiding __tri_storage created
for curve segments.
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separate some arrays.
Differential Revision: https://developer.blender.org/D2016
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It's no longer a pre-computed data and just a storage of triangle
coordinates which are faster to access to.
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This commit makes it so casting subsurface rays will totally ignore all
the BVH nodes and primitives which do not belong to a current object,
making it much simpler traversal code and reduces number of intersection
tests.
Reviewers: brecht, juicyfruit, dingto, lukasstockner97
Differential Revision: https://developer.blender.org/D1823
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Notes:
- There is still some bvh cache code, but that is from the engines initial commit, we might clean this up further or keep it.
- Changes in util_cache.h/.c are kept, this might be re-used in the future.
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Previous idea behind having vector during building and array for actual storage
was needed in order to minimize amount of re-allocations happening during the
build, but it lead to double memory overhead used by those arrays at the vector
to array conversion stage.
Issue with such approach was that for BVH without spatial split size of arrays
is known in advance and it never changes, which made vector to array conversion
totally redundant.
Also after testing with several rather complex from spatial split scenes (such
as trees) it seems even conservative approach of reallocation (when we perform
re-allocation when leaf does not fit into the memory) doesn't give measurable
difference in time.
This makes it so we can switch to array, which will avoid unneeded memory
re-allocations when spatial split is disabled without harming other cases.
it's a bit difficult to measure exact benefit of this change on our production
files here, but depending on the scene it might give quite reasonable memory
save.
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Still need to solve issues with reading old cache with new builds.
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This way we can get rid of inefficient memory usage caused by BVH boundbox
part being unused by leaf nodes but still being allocated for them. Doing
such split allows to save 6 of float4 values for QBVH per leaf node and 3
of float4 values for regular BVH per leaf node.
This translates into following memory save using 01.01.01.G rendered
without hair:
Device memory size Device memory peak Global memory peak
Before the patch: 4957 5051 7668
With the patch: 4467 4562 7332
The measurements are done against current master. Still need to run speed tests
and it's hard to predict if it's faster or not: on the one hand leaf nodes are
now much more coherent in cache, on the other hand they're not so much coherent
with regular nodes anymore.
Reviewers: brecht, juicyfruit
Subscribers: venomgfx, eyecandy
Differential Revision: https://developer.blender.org/D1236
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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.
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The issue was caused by mismatch in how aligned triangles storage was
filled in during BVH construction and how it was used during rendering.
Basically, i was leaving uninitialized storage for triangles when
there was deformation motion blur detected for the mesh. Was likely
some sort of optimization, but in fact it's still possible that regular
triangles would be needed for rendering.
So now we're storing aligned storage for all triangle primitives and
only skipping motion triangles (the deformation motion blur flag from
mesh is now ignored).
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Ideally we should get rid of those temporary vectors anyway, but
it's not so trivial because of the alignment. For untl then we'll
just have a bit worse solution. This part of code is not the root
of the issue of memory spikes for now anyway.
But since we're getting rid of temporary memory earlier actual spike
is a bit smaller as now. For example in franck_sheep file it's now
5489.69MB vs. previously 5599.90MB.
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This will save some memory during BVH Build.
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This way we save 3 bytes per BVH node while building BVH, which overall
gives 100Mb memory save when preparing Frank for render.
It's not really much comparing to overall memory usage (which is 11Gb
during scene preparation here) but still doesn't harm to have solved.
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Handy for troubleshooting.
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It's apparently not nice to access 0th element of zero-size vector in C++.
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The idea of this change is make it possible to split leaf nodes by primitive
type, making leaf containing primitives of the same type.
This would become handy when working on a single ray to multiple triangles
intersection code, plus with careful implementation it might give some extra
benefits on BVH traversal code by avoiding primitive type fetch and check for
each primitive in the node. But that's a bit tricky to have benefits on this
change only because depth of BVH increases.
This option is not exposed to the interface at all and not used even secretly,
the commit is only needed to help working further in this direction without
messing around with local patches and worrying of them running out of date.
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This is harmless for now because tail of the node is zero in there, but better
to fix it early so in the case of extending BVH nodes this code doesn't give
issues.
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This commit implements traversal for QBVH tree, which is based on the old loop
code for traversal itself and Embree for node intersection.
This commit also does some changes to the loop inspired by Embree:
- Visibility flags are only checked for primitives.
Doing visibility check for every node cost quite reasonable amount of time
and in most cases those checks are true-positive.
Other idea here would be to do visibility checks for leaf nodes only, but
this would need to be investigated further.
- For minimum hair width we extend all the nodes' bounding boxes.
Again doing curve visibility check is quite costly for each of the nodes and
those checks returns truth for most of the hierarchy anyway.
There are number of possible optimization still, but current state is good
enough in terms it makes rendering faster a little bit after recent watertight
commit.
Currently QBVH is only implemented for CPU with SSE2 support at least. All
other devices would need to be supported later (if that'd make sense from
performance point of view).
The code is enabled for compilation in kernel. but blender wouldn't use it
still.
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The idea is to make sure those childs would never be intersected with a ray
in order to make it so kernel never worries about number of child nodes.
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Using this paper: Sven Woop, Watertight Ray/Triangle Intersection
http://jcgt.org/published/0002/01/05/paper.pdf
This change is expected to address quite reasonable amount of reports from the
bug tracker, plus it might help reducing the noise in some scenes.
Unfortunately, it's currently about 7% slower than the previous solution with
pre-computed triangle plane equations, but maybe with some smart tweaks to the
code (tests reshuffle, using SIMD in a nice way or so) we can avoid the speed
regression.
But perhaps smartest thing to do here would be to change single triangle / ray
intersection with multiple triangles / ray intersections. That's how Embree does
this and it's watertight single ray intersection is not any faster that this.
Currently only triangle intersection is modified accordingly to the paper, in
the future we would also want to modify the node / ray intersection.
Reviewers: brecht, juicyfruit
Subscribers: dingto, ton
Differential Revision: https://developer.blender.org/D819
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The idea is to store visibility flags for leaf nodes only since visibility check
for inner nodes costs too much for QBVH hence it is not optimal to perform.
Leaf QBVH nodes have plenty of space to store all sort of flags, so we can make
nodes one element smaller, saving noticeable amount of memory.
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Previously offsets were calculated based on the BVH node size,
which is wrong and real PITA in cases when some extra data is
to be added into (or removed from) the node.
Now use offsets which are not calculated form the node size.
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This solves quite an over-allocation in BVH instances packing code,
unfortunately, it's not a magic bullet to solve memory bump caused
by the recent QBVH changes.
For that we'll likely need to decouple storage for leaf and inner
nodes. However, it's not really clear for now if it's something
important since that'd still be just a fraction of memory comparing
to all the hi-res textures.
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Title says it all, quite straightforward implementation.
Would only mention that there's a bit of code duplication around packing node
into pack.nodes. Trying to de-duplicate it ends up in quite hairy code (like
functions with loads of arguments some of which could be NULL in certain
circumstances etc..). Leaving solving this duplication for later.
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Before all the nodes were counted and allocated, leading to situations when
bunch of allocated memory is not used because reasonable amount of nodes are
simply ignored.
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Before this Cycles used to try using the cache even so it knew for the
fact that reading it from the disk failed. This change doesn't make it
more stable if someone will try to trick Cycles and give malformed data
but it solves general cases when Blender crashed during the cache write
and will preserve rendering from crashing when trying to use that partial
cache.
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attribute.
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