This commit uses two changes to improve the performance of the point
instance node.
**Prevent Reallocations**
At 64 bytes, the transform matrix for every instance is rather large,
so reallocating the vector as it grows can become a performance bottle-
neck. This commit reserves memory for the instances that will be added
to prevent unecessary reallocations as the instance vector grows.
In a test with 4 million instances of 3 objects in a collection, the
node was about 40% faster, from 370ms to 270ms for the node.
**Parallelization**
Currently the instances are added by appending to a vector. By changing
this slightly to fill indices instead, we can parallelize the operation
so that multiple threads can fill data at the same time. Tested on a
Ryzen 3700x, this reduced the runtime from the above 270ms to 44ms
average, bringing the total speedup to ~8x.
Note that displaying the instances in the viewport is still much slower
than the calculations in node, this change doesn't affect that.
The main goal of this refactor is to not store Object/Collection
pointers for every individual instance. Instead instances now
store a handle for the referenced data. The actual Object/Collection
pointers are stored in a new `InstanceReference` class.
This refactor also allows for some better optimizations further down
the line, because one does not have to search through all instances
anymore to find what data is instanced.
Furthermore, this refactor makes it easier to support instancing
`GeometrySet` or any other data that has to be owned by the
`InstancesComponent`.
Differential Revision: https://developer.blender.org/D11125
Though to my knowledge we haven't had a report about this yet, this
looks like a clear oversight-- the ids are just more data stored by the
instances component, and should be cleared and copied like other data.
This might have resulted in incorrect random IDs for instances in
renderers in some cases where the component had to be copied.
Previously, the spreadsheet editor could only show data of the original
and of the final evaluated object. Now it is possible to show the data
at some intermediate stages too.
For that the mode has to be set to "Node" in the spreadsheet editor.
Furthermore, the preview of a specific node has to be activated by
clicking the new icon in the header of geometry nodes.
The exact ui of this feature might be refined in upcoming commits.
It is already very useful for debugging node groups in it's current
state though.
Differential Revision: https://developer.blender.org/D10875
Currently the implementations specific to each geometry type are in
the same file. This makes it difficult to tell which code is generic
for all component types and which is specific to a certain type.
The two files, `attribute_access.cc`, and `geometry_set.cc` are
also getting quite long.
This commit splits up the implementation for every geometry component,
and adds an internal header file for the common parts of the attribute
access code. This was discussed with Jacques Lucke.
