Often it would be beneficial to avoid the virtual array implementation
in `geometry_component_curve.cc` that flattens an attribute for every
spline and instead read an attribute separately for every input spline.
This commit implements functions to do that.
The downside is some code duplication-- we now have two places handling
this conversion. However, we can head in this general direction for the
attribute API anyway and support accessing attributes in smaller
contiguous chunks where necessary.
No functional changes in this commit.
Differential Revision: https://developer.blender.org/D11456
With this patch you will be able to add and remove attributes from curve
data inside of geometry nodes. The following is currently implemented:
* Adding attributes with any data type to splines or spline points.
* Support for working with multiple splines at the same time.
* Interaction with the three builtin point attributes.
* Resampling attributes in the resample node.
The following is not implemented in this patch:
* Joining attributes when joining splines with the join geometry node.
* Domain interpolation between spline and point domains.
* More efficient ways to call attribute operations once per spline.
Differential Revision: https://developer.blender.org/D11251
This code in the geometry set header was not directly related to
geometry sets, it makes more sense in the attribute access header.
This makes it clearer that code for geometry components uses attribute
code, rather than the other way around. It also allows adding more
functionality to `BKE_attribute_access.hh` that depends on these things
without including `BKE_geometry_set.hh` there.
A virtual array is a data structure that is similar to a normal array
in that its elements can be accessed by an index. However, a virtual
array does not have to be a contiguous array internally. Instead, its
elements can be layed out arbitrarily while element access happens
through a virtual function call. However, the virtual array data
structures are designed so that the virtual function call can be avoided
in cases where it could become a bottleneck.
Most commonly, a virtual array is backed by an actual array/span or
is a single value internally, that is the same for every index.
Besides those, there are many more specialized virtual arrays like the
ones that provides vertex positions based on the `MVert` struct or
vertex group weights.
Not all attributes used by geometry nodes are stored in simple contiguous
arrays. To provide uniform access to all kinds of attributes, the attribute
API has to provide virtual array functionality that hides the implementation
details of attributes.
Before this refactor, the attribute API provided its own virtual array
implementation as part of the `ReadAttribute` and `WriteAttribute` types.
That resulted in unnecessary code duplication with the virtual array system.
Even worse, it bound many algorithms used by geometry nodes to the specifics
of the attribute API, even though they could also use different data sources
(such as data from sockets, default values, later results of expressions, ...).
This refactor removes the `ReadAttribute` and `WriteAttribute` types and
replaces them with `GVArray` and `GVMutableArray` respectively. The `GV`
stands for "generic virtual". The "generic" means that the data type contained
in those virtual arrays is only known at run-time. There are the corresponding
statically typed types `VArray<T>` and `VMutableArray<T>` as well.
No regressions are expected from this refactor. It does come with one
improvement for users. The attribute API can convert the data type
on write now. This is especially useful when writing to builtin attributes
like `material_index` with e.g. the Attribute Math node (which usually
just writes to float attributes, while `material_index` is an integer attribute).
Differential Revision: https://developer.blender.org/D10994
When a function is executed for many elements (e.g. per point) it is often the case
that some parameters are different for every element and other parameters are
the same (there are some more less common cases). To simplify writing such
functions one can use a "virtual array". This is a data structure that has a value
for every index, but might not be stored as an actual array internally. Instead, it
might be just a single value or is computed on the fly. There are various tradeoffs
involved when using this data structure which are mentioned in `BLI_virtual_array.hh`.
It is called "virtual", because it uses inheritance and virtual methods.
Furthermore, there is a new virtual vector array data structure, which is an array
of vectors. Both these types have corresponding generic variants, which can be used
when the data type is not known at compile time. This is typically the case when
building a somewhat generic execution system. The function system used these virtual
data structures before, but now they are more versatile.
I've done this refactor in preparation for the attribute processor and other features of
geometry nodes. I moved the typed virtual arrays to blenlib, so that they can be used
independent of the function system.
One open question for me is whether all the generic data structures (and `CPPType`)
should be moved to blenlib as well. They are well isolated and don't really contain
any business logic. That can be done later if necessary.
This node allows sampling a texture for every vertex based on some
mapping attribute. Typical attribute names are the name of a uv map
(e.g. "UVMap") and "position". However, every attribute that can be
converted to a vector implicitly is supported.
It should be noted that as of right now, uv map attributes can only be
accessed after a Point Distribute node.
Ref T82584.
Differential Revision: https://developer.blender.org/D10121
Previously, the span returned by `WriteAttribute`s might not contain the
current value of the attribute for performance reasons. To avoid some
bugs, the span now always contains the old values (they might have to
be copied over from the internal storage, dependending on how the
attribute is stored).
The old behavior is still available with the `get_span_for_write_only`
method. The span that it returns might not contain the current
attribute values. Therefore, it should only be used when you want
to overwrite an attribute without looking at the old values.
Currently, the random attribute node doesn't work well for most
workflows because for any change in the input data it outputs
completely different results.
This patch adds an implicit seed attribute input to the node, referred
to by "id". The attribute is hashed for each element using the CPPType
system's hash method, meaning the attribute can have any data type.
Supporting any data type is also important so any attribute can be
copied into the "id" attribute and used as a seed.
The "id" attribute is an example of a "reserved name" attribute,
meaning attributes with this name can be used implicitly by nodes like
the random attribute node. Although it makes it a bit more difficult
to dig deeper, using the name implicitly rather than exposing it as an
input should make the system more accessible and predictable.
Differential Revision: https://developer.blender.org/D9832
This adds a boolean attribute and custom data type, to be used in the
point separate node. It also adds it as supported data types in the
random attribute and attribute fill nodes.
There are more clever ways of storing a boolean attribute that make
more sense in certain situations-- sets, bitfields, and others, this
commit keeps it simple, saving those changes for when there is a proper
use case for them. In any case, we will still probably always want the
idea of a boolean attribute.
Differential Revision: https://developer.blender.org/D9818
This is the initial merge from the geometry-nodes branch.
Nodes:
* Attribute Math
* Boolean
* Edge Split
* Float Compare
* Object Info
* Point Distribute
* Point Instance
* Random Attribute
* Random Float
* Subdivision Surface
* Transform
* Triangulate
It includes the initial evaluation of geometry node groups in the Geometry Nodes modifier.
Notes on the Generic attribute access API
The API adds an indirection for attribute access. That has the following benefits:
* Most code does not have to care about how an attribute is stored internally.
This is mainly necessary, because we have to deal with "legacy" attributes
such as vertex weights and attributes that are embedded into other structs
such as vertex positions.
* When reading from an attribute, we generally don't care what domain the
attribute is stored on. So we want to abstract away the interpolation that
that adapts attributes from one domain to another domain (this is not
actually implemented yet).
Other possible improvements for later iterations include:
* Actually implement interpolation between domains.
* Don't use inheritance for the different attribute types. A single class for read
access and one for write access might be enough, because we know all the ways
in which attributes are stored internally. We don't want more different internal
structures in the future. On the contrary, ideally we can consolidate the different
storage formats in the future to reduce the need for this indirection.
* Remove the need for heap allocations when creating attribute accessors.
It includes commits from:
* Dalai Felinto
* Hans Goudey
* Jacques Lucke
* Léo Depoix
