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WIP: Volume grid attribute support in geometry nodes #110044

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Lukas Tönne wants to merge 130 commits from LukasTonne/blender:geometry-nodes-flip into main
pull from: LukasTonne/blender:geometry-nodes-flip
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Lukas Tönne commented 2023-07-13 08:43:03 +02:00
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Adds attributes to the VolumeComponent in geometry sets. Each grid is presented as an attribute, with the condition that all grids in the VolumeGridVector must share the same transform, topology, and active voxel set.

A specialized VArray implementation is added for accessing values stored in a grid, and associated built-in values such as voxel coordinates/positions.
image

A number of dummy nodes have been added as well. For the most part these are "aspirational" and not yet implemented, but they provide a test bed and motivation for features. The set of nodes is roughly what would be required for a basic FLIP/PIC fluid solver, on top of attribute support.image

Adds attributes to the `VolumeComponent` in geometry sets. Each grid is presented as an attribute, with the condition that all grids in the `VolumeGridVector` must share the same transform, topology, and active voxel set. A specialized `VArray` implementation is added for accessing values stored in a grid, and associated built-in values such as voxel coordinates/positions. ![image](/attachments/a39a92c9-3dff-4cf0-a1dd-34f4620a90e0) A number of dummy nodes have been added as well. For the most part these are "aspirational" and not yet implemented, but they provide a test bed and motivation for features. The set of nodes is roughly what would be required for a basic FLIP/PIC fluid solver, on top of attribute support.![image](/attachments/71190c90-dbd6-4a92-b0af-c5b9ef35178b)
image.png
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Lukas Tönne added 17 commits 2023-07-13 08:43:14 +02:00
Lukas Tönne added 1 commit 2023-07-13 09:31:54 +02:00
Lukas Tönne added 1 commit 2023-07-13 10:39:29 +02:00
Iliya Katushenock added the
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Iliya Katushenock added this to the Nodes & Physics project 2023-07-13 10:53:57 +02:00
Hans Goudey commented 2023-07-13 13:18:10 +02:00
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I think we should have some design discussions about this, because there are points where it diverges from #103248 in some fairly fundamental ways. I won't write that all here though, since it should probably happen elsewhere.

I think we should have some design discussions about this, because there are points where it diverges from #103248 in some fairly fundamental ways. I won't write that all here though, since it should probably happen elsewhere.
Lukas Tönne commented 2023-07-13 13:52:07 +02:00
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there are points where it diverges from #103248 in some fairly fundamental ways

If you are referring to the "Grid Value" and "Set Grid Value" nodes in the screenshot: Those are already outdated again. I was playing around with the idea of a single grid per volume, but went back to the "grids are attributes" concept from the #103248 design (e.g. grid lookup by attribute id). I wanted to update the screenshots but then ran into #110052 on my work machine. Besides that, i'm playing fast and loose with design here, i just want to get something working. It's more about learning how to access OpenVDB grids and integrate with the rest of GN.

> there are points where it diverges from #103248 in some fairly fundamental ways If you are referring to the "Grid Value" and "Set Grid Value" nodes in the screenshot: Those are already outdated again. I was playing around with the idea of a single grid per volume, but went back to the "grids are attributes" concept from the #103248 design (e.g. [grid lookup by attribute id](https://projects.blender.org/blender/blender/src/commit/0ae4ac4b64ea9235da11a0b9da07c7d282dce33a/source/blender/blenkernel/BKE_volume_attribute.hh#L228)). I wanted to update the screenshots but then ran into #110052 on my work machine. Besides that, i'm playing fast and loose with design here, i just want to get _something_ working. It's more about learning how to access OpenVDB grids and integrate with the rest of GN.
Lukas Tönne commented 2023-07-13 15:50:38 +02:00
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Had some discussion with Hans about how grids with different topology might work together as attributes. Grids don't necessarily have to have the same active voxel layout to work together, sampling grids is fast. If transforms are the same, which is easy to ensure, grid access should be well optimized by OpenVDB.

The difficulty is that domain size (number of active voxels) is not well defined when combining multiple grids. One possibility is to define domain size of the entire Volume as the maximum number of active voxels among all its grids. OpenVDB will use the background value when sampling at a coordinate that is not active on a grid. That leaves the question of what get(int64_t index) means, if index does not map to a consistent active voxel for different grids. The recommendation is to use (i,j,k) coordinates for openvdb grid sampling, but VArrays work with a 1D index space.

Another possibility i've been considering is to move up one conceptual layer and define a dedicated Field type for voxels instead of just a VArray. We'd probably need to specialize the FieldEvaluator, which could switch to grid evaluation based on the VolumeFieldContext.

Had some discussion with Hans about how grids with different topology might work together as attributes. Grids don't necessarily have to have the same active voxel layout to work together, sampling grids is fast. If transforms are the same, which is easy to ensure, grid access should be well optimized by OpenVDB. The difficulty is that domain size (number of active voxels) is not well defined when combining multiple grids. One possibility is to define domain size of the entire Volume as the maximum number of active voxels among all its grids. OpenVDB will use the background value when sampling at a coordinate that is not active on a grid. That leaves the question of what `get(int64_t index)` means, if `index` does not map to a consistent active voxel for different grids. The recommendation is to use (i,j,k) coordinates for openvdb grid sampling, but `VArrays` work with a 1D index space. Another possibility i've been considering is to move up one conceptual layer and define a dedicated `Field` type for voxels instead of just a `VArray`. We'd probably need to specialize the FieldEvaluator, which could switch to grid evaluation based on the `VolumeFieldContext`.
Hans Goudey commented 2023-07-13 16:39:00 +02:00
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The difficulty is that domain size (number of active voxels) is not well defined when combining multiple grids

I guess it's mostly necessary to know the domain size when creating the virtual array? That's essentially the problem with flattening things out I guess. I don't think we can really rely on having a meaningful domain size value for the whole volume data-block. That might be inconvenient with some attribute code that assumes this, but I think there's not much way around that.

Another possibility i've been considering is to move up one conceptual layer and define a dedicated Field type for voxels instead of just a VArray. We'd probably need to specialize the FieldEvaluator, which could switch to grid evaluation based on the VolumeFieldContext.

I think this makes a lot of sense!

This is also how I imagined evaluating an arbitrary field to create a grid in the capture and store named attribute nodes-- the values would be sampled on the topology of an existing grid that's part of the field context. If the field refers to a volume grid directly though, that's an important optimization that will probably be essential for simple cases like passing a grid to the sample volume node.

Going a bit further, I'd imagine this allows the divergence and gradient nodes to be field input nodes that don't require a volume input.

EDIT: we may still want to have a virtual array implementation for grids though, to simplify displaying values in the spreadsheet.

> The difficulty is that domain size (number of active voxels) is not well defined when combining multiple grids I guess it's mostly necessary to know the domain size when creating the virtual array? That's essentially the problem with flattening things out I guess. I don't think we can really rely on having a meaningful domain size value for the whole volume data-block. That might be inconvenient with some attribute code that assumes this, but I think there's not much way around that. > Another possibility i've been considering is to move up one conceptual layer and define a dedicated `Field` type for voxels instead of just a `VArray`. We'd probably need to specialize the FieldEvaluator, which could switch to grid evaluation based on the `VolumeFieldContext`. I think this makes a lot of sense! This is also how I imagined evaluating an arbitrary field to create a grid in the capture and store named attribute nodes-- the values would be sampled on the topology of an existing grid that's part of the field context. If the field refers to a volume grid directly though, that's an important optimization that will probably be essential for simple cases like passing a grid to the sample volume node. Going a bit further, I'd imagine this allows the divergence and gradient nodes to be field input nodes that don't require a volume input. EDIT: we may still want to have a virtual array implementation for grids though, to simplify displaying values in the spreadsheet.
Hans Goudey commented 2023-07-13 16:40:24 +02:00
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Also, I think for volumes the implicit position attribute you have here doesn't quite work, since it relies on the matching topology and "domain sizes".

Also, I think for volumes the implicit position attribute you have here doesn't quite work, since it relies on the matching topology and "domain sizes".
Lukas Tönne added 1 commit 2023-07-14 09:22:45 +02:00
Lukas Tönne added 1 commit 2023-07-15 02:19:27 +02:00
Lukas Tönne added 1 commit 2023-07-16 19:16:36 +02:00
Lukas Tönne added 1 commit 2023-07-16 19:50:34 +02:00
Lukas Tönne added 1 commit 2023-07-16 21:44:47 +02:00
Lukas Tönne added 1 commit 2023-07-17 00:11:45 +02:00
Lukas Tönne added 1 commit 2023-07-17 09:30:58 +02:00
Lukas Tönne added 1 commit 2023-07-18 01:14:29 +02:00
Lukas Tönne added 1 commit 2023-07-18 22:07:58 +02:00 
The new Grid and GridMask classes will act similar to VArrays during
field evaluation. The VolumeGrid struct is equivalent to
CustomDataLayers, it provides the attribute inputs for the field graph.
Lukas Tönne added 1 commit 2023-07-19 10:22:38 +02:00
Lukas Tönne added 2 commits 2023-07-19 18:32:11 +02:00
Lukas Tönne added 1 commit 2023-07-22 12:45:34 +02:00
Lukas Tönne added 2 commits 2023-07-22 17:08:54 +02:00
Lukas Tönne added 2 commits 2023-07-23 11:45:10 +02:00
Lukas Tönne added 1 commit 2023-07-23 16:14:03 +02:00
Lukas Tönne added 1 commit 2023-07-24 09:01:19 +02:00
Lukas Tönne added 1 commit 2023-07-24 14:19:55 +02:00
Lukas Tönne added 1 commit 2023-07-24 14:29:30 +02:00
Lukas Tönne added 1 commit 2023-07-24 15:18:14 +02:00
Lukas Tönne added 1 commit 2023-07-26 09:01:54 +02:00
Lukas Tönne added 2 commits 2023-07-26 20:14:51 +02:00
Lukas Tönne added 1 commit 2023-07-30 10:19:13 +02:00
Lukas Tönne added 1 commit 2023-08-05 12:45:07 +02:00 
OpenVDB is heavily templated and can dramatically increase build times
and memory requirement, if OpenVDB headers are included in too many
places. The solution is to avoid including openvdb.h in other header
files and only do this in .cc source files where the implementation is
really needed. The BLI_volume.hh header now only forward-declares
the OpenVDB types.
Lukas Tönne added 2 commits 2023-08-05 13:34:09 +02:00
Lukas Tönne added 3 commits 2023-08-05 14:43:32 +02:00
Lukas Tönne added 1 commit 2023-08-05 16:19:49 +02:00
Lukas Tönne added 1 commit 2023-08-05 17:37:57 +02:00
Lukas Tönne added 1 commit 2023-08-06 13:52:05 +02:00
Lukas Tönne added 1 commit 2023-08-06 13:58:07 +02:00
Lukas Tönne added 1 commit 2023-08-06 16:35:42 +02:00
Lukas Tönne added 1 commit 2023-08-07 00:34:01 +02:00
Lukas Tönne added 1 commit 2023-08-07 09:07:38 +02:00
Lukas Tönne added 1 commit 2023-08-07 09:19:20 +02:00
Lukas Tönne added 1 commit 2023-08-07 09:24:35 +02:00 
This assert makes sense for VArrays which are pre-allocated, but grids
change size dynamically and the destination can be just an empty grid.
Lukas Tönne added 1 commit 2023-08-07 10:30:49 +02:00
Lukas Tönne added 1 commit 2023-08-07 10:42:30 +02:00
Lukas Tönne added 1 commit 2023-08-07 14:05:44 +02:00
Lukas Tönne added 1 commit 2023-08-07 16:31:01 +02:00 
Static type dispatchers like `field_to_static_type` and
`grid_to_static_type` generate a lot of code, leading to combinatorial
explosion when they are nested. This can easily overwhelm the linker
and break the build, in addition to making it slow.
Lukas Tönne added 1 commit 2023-08-07 16:42:59 +02:00
Lukas Tönne added 1 commit 2023-08-09 15:09:58 +02:00
Lukas Tönne added 1 commit 2023-08-10 08:00:10 +02:00
Lukas Tönne added 1 commit 2023-08-10 08:59:36 +02:00 
Moving a grid pointer to the resource scope invalidates the pointer,
have to use the result of scope.add to return the actual grid.
Lukas Tönne added 1 commit 2023-08-10 10:46:31 +02:00
Lukas Tönne added 4 commits 2023-08-13 14:45:59 +02:00
Lukas Tönne added 2 commits 2023-08-13 18:08:57 +02:00
Lukas Tönne added 1 commit 2023-08-14 09:44:44 +02:00 
Grids can have active nodes with all-constant values, in which case
OpenVDB will optimize away leaf buffers. To be able to evaluate the
multifunction on each voxel we first need to voxelize the output grid.
Lukas Tönne added 1 commit 2023-08-14 10:17:00 +02:00
Lukas Tönne added 3 commits 2023-08-15 11:45:27 +02:00 
This needs to be unified, for now just make it work.
The selection grid can be empty but still `true` everywhere, in which
case the full mask should be used.
Lukas Tönne added 1 commit 2023-08-17 08:53:51 +02:00 
This makes it easier to load compatible grids from files and use
existing OpenVDB tools and algorithms. It requires some converter utils
to reinterpret vector types like `openvdb::Vec3f` as the equivalent
Blender vector types.
Lukas Tönne force-pushed geometry-nodes-flip from 9020dc99d2 to 3d99cd075d 2023-08-17 15:52:05 +02:00 Compare
Lukas Tönne added 1 commit 2023-08-17 17:35:32 +02:00 
Bool grids also effectively use the same LeafBuffer type as MaskGrids,
which directly exposes the bit fields of the activation state (WordType,
unsigned long int).
Lukas Tönne force-pushed geometry-nodes-flip from d70d9ffa39 to 36fedfa64f 2023-08-17 18:32:49 +02:00 Compare
Lukas Tönne added 2 commits 2023-08-18 10:34:30 +02:00
Lukas Tönne force-pushed geometry-nodes-flip from 3a3532a0e4 to 67bd1671cf 2023-08-18 12:45:08 +02:00 Compare
Lukas Tönne added 1 commit 2023-08-18 13:57:38 +02:00
Lukas Tönne added 1 commit 2023-08-18 14:36:38 +02:00
Lukas Tönne added 1 commit 2023-08-18 14:41:29 +02:00
Lukas Tönne added 1 commit 2023-08-18 15:31:38 +02:00 
A MaskGrid can be represented simply as a volume::Grid<bool>.
Lukas Tönne added 2 commits 2023-08-21 09:25:52 +02:00 
Example: voxel positions can be a virtual grid without actual voxel
values stored in a grid. As a virtual grid with a function
implementation they can be evaluated at any location without requiring
grid storage.
Lukas Tönne added 1 commit 2023-08-21 18:07:59 +02:00
Lukas Tönne added 2 commits 2023-08-27 18:52:28 +02:00
Lukas Tönne added 2 commits 2023-08-27 23:32:15 +02:00
Lukas Tönne added 2 commits 2023-08-28 16:44:57 +02:00
Lukas Tönne added 1 commit 2023-08-28 18:06:31 +02:00 
Grids are stored in shared_ptr and eventually freed using delete.
Lukas Tönne added 1 commit 2023-08-28 22:02:35 +02:00
Lukas Tönne added 1 commit 2023-08-29 09:12:50 +02:00
Lukas Tönne added 1 commit 2023-09-08 19:43:52 +02:00
Lukas Tönne added 1 commit 2023-09-08 22:10:11 +02:00
Lukas Tönne added 1 commit 2023-09-09 09:23:30 +02:00
Lukas Tönne added 1 commit 2023-09-09 10:01:28 +02:00
Lukas Tönne added 1 commit 2023-09-09 11:22:18 +02:00 
When evaluating input volume fields the output buffers are initialized
as empty grids. In order to have leaf node buffers to store values in
the output buffers needs to have the combined topology of all input
grids.
Lukas Tönne added 1 commit 2023-09-09 14:02:48 +02:00
Lukas Tönne added 1 commit 2023-09-09 19:00:25 +02:00
Lukas Tönne added 1 commit 2023-09-10 14:01:08 +02:00 
It's unclear why makesrna needs this implementation in the first place
(maybe the source crawling preprocess adds this dependency somehow).
Linking to bf_blenlib does not solve the problem, the only thing that
seems to work is adding a stub in bf_rna itself.
Lukas Tönne added 1 commit 2023-09-10 14:09:11 +02:00
Lukas Tönne added 1 commit 2023-09-10 15:02:52 +02:00
Lukas Tönne added 1 commit 2023-09-10 15:41:45 +02:00
Lukas Tönne added 1 commit 2023-09-10 23:29:07 +02:00
Lukas Tönne added 1 commit 2023-09-11 10:35:30 +02:00
Lukas Tönne added 1 commit 2023-09-11 11:06:20 +02:00
Lukas Tönne added 1 commit 2023-09-12 09:30:44 +02:00
Lukas Tönne added 1 commit 2023-09-12 22:42:37 +02:00
Lukas Tönne added 1 commit 2023-09-13 08:10:50 +02:00
Lukas Tönne added 1 commit 2023-09-14 20:21:22 +02:00
Lukas Tönne added 1 commit 2023-09-15 12:01:07 +02:00
Lukas Tönne added 1 commit 2023-09-15 12:05:54 +02:00
Lukas Tönne commented 2023-09-15 14:06:58 +02:00
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Lukas Tönne added 1 commit 2023-09-15 18:01:53 +02:00
Lukas Tönne added 1 commit 2023-09-16 10:26:17 +02:00 
This reverts commit 190035a1e8.
Lukas Tönne added 1 commit 2023-09-16 10:43:39 +02:00
Lukas Tönne added 1 commit 2023-09-16 23:37:27 +02:00
Lukas Tönne added 1 commit 2023-09-17 09:00:46 +02:00
Lukas Tönne added 1 commit 2023-09-17 09:01:20 +02:00
Hans Goudey commented 2024-02-14 16:31:34 +01:00
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Superseded by #116021

Superseded by #116021
Hans Goudey closed this pull request 2024-02-14 16:31:36 +01:00

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