WIP: Make ComponentAttributeAccessor handle active/default_color_attribute #109083

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Martijn Versteegh wants to merge 4 commits from Baardaap/blender:addremovetrigger into blender-v3.6-release

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When Geometry Nodes created or deleted attributes it didn't handle
the active/default_color_attribute strings on Mesh. This lead to
Meshes with color attributes but without active/default_color_attribute
set, which is a regression from previous blender versions where newly
created color attributes are always set to active/default if they were the
first created color attribute.

When using GN to colorize point cloud data, for example, it's very
convenient if the created color_attribute is also used in solid mode attribute
coloring.

When Geometry Nodes created or deleted attributes it didn't handle the active/default_color_attribute strings on Mesh. This lead to Meshes with color attributes but without active/default_color_attribute set, which is a regression from previous blender versions where newly created color attributes are always set to active/default if they were the first created color attribute. When using GN to colorize point cloud data, for example, it's very convenient if the created color_attribute is also used in solid mode attribute coloring.
Martijn Versteegh added 1 commit 2023-06-17 18:08:46 +02:00
90e509d86d Make ComponentAttributeAccessor handle active/default_color_attribute
When Geometry Nodes created or deleted attributes it didn't handle
the active/default_color_attribute strings on Mesh. This lead to
Meshes with color attributes but without active/default_color_attribute
set, which is a regression from previous blender versions where newly
created color attributes are always set to active/default.
Author
Member

I think this is a better way to do what #109067 did as well.

I think this is a better way to do what #109067 did as well.
Martijn Versteegh added 1 commit 2023-06-17 18:11:27 +02:00
Martijn Versteegh added the
Module
Nodes & Physics
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Geometry Nodes
labels 2023-06-17 18:17:18 +02:00
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Member

Iliya suggested (i the chat) to use 'handler' instead of 'trigger' for the function names. Which is better I agree.

Also I have my doubts about the delete handler because:

  • it gets called for any deleted attribute regardless of type (the type isn't readily available)
  • it does unconditional strncmp for every deleted attribute, which is maybe too slow?
  • as it currently is there is no way to delete attributes from GN I think? So they only get deleted to just get recreated immediately.

But is does seem more 'correct' this way and I'm afraid not clearing those strings on attrib delete will come back to bite us in the ass later.

Now that I think of it... I'm not really sure the delete handler is even correct. As it uses the AttributeIDRef which points to the just deleted attribute. And it's name_ member probably points into the name of the deleted layer. Which could be the wrong layer name now that I think of it (because of the reordering of CD layers on remove). The delete handler would need to be called before deleting the layer, which is a bit more hard to integrate..

ok. back to the drawing board I guess. But I'd still very much appreciate some feedback on if this approach seems feasible and if it's something we want to have (setting the first created layer to active)

Iliya suggested (i the chat) to use 'handler' instead of 'trigger' for the function names. Which is better I agree. Also I have my doubts about the delete handler because: - it gets called for *any* deleted attribute regardless of type (the type isn't readily available) - it does unconditional strncmp for every deleted attribute, which is maybe too slow? - as it currently is there is no way to delete attributes from GN I think? So they only get deleted to just get recreated immediately. But is does seem more 'correct' this way and I'm afraid not clearing those strings on attrib delete will come back to bite us in the ass later. Now that I think of it... I'm not really sure the delete handler is even correct. As it uses the AttributeIDRef which points to the just deleted attribute. And it's name_ member probably points into the name of the deleted layer. Which could be the wrong layer name now that I think of it (because of the reordering of CD layers on remove). The delete handler would need to be called *before* deleting the layer, which is a bit more hard to integrate.. ok. back to the drawing board I guess. But I'd still very much appreciate some feedback on if this approach seems feasible and if it's something we want to have (setting the first created layer to active)
Martijn Versteegh added 1 commit 2023-06-17 21:03:43 +02:00
23356efa98 -Trigger -> Handler
-call remove handler before removing the layer
Martijn Versteegh added 1 commit 2023-06-17 21:23:25 +02:00
Author
Member

I think I solved the issue with the remove handler being wrong.

I think I solved the issue with the remove handler being wrong.
Hans Goudey reviewed 2023-06-18 01:21:07 +02:00
@ -1082,6 +1082,38 @@ class VertexGroupsAttributeProvider final : public DynamicAttributesProvider {
*/
static ComponentAttributeProviders create_attribute_providers_for_mesh()
{
static AttributeAddHandler mesh_add_handler =
Member

To me the need for a concept like "Trigger" suggests the system is getting a bit too complex. Seems like it might fit a bit better in the existing CustomDataAttributeProvider::try_delete() function.

To me the need for a concept like "Trigger" suggests the system is getting a bit too complex. Seems like it might fit a bit better in the existing `CustomDataAttributeProvider::try_delete()` function.
Author
Member

I thought about that. But the problem is that the active/default is set on the mesh, and not on the CustomData level
I'll look at it again, but I think CustomDataAttributeProvider just links to the CustomDataLayer and has no easy way to get back to the owning mesh.

Furthermore CustomDataAttributeProvider is also used for Curves and PointClouds, but this functionality is only needed for Mesh.

I thought about that. But the problem is that the active/default is set on the mesh, and not on the CustomData level I'll look at it again, but I think CustomDataAttributeProvider just links to the CustomDataLayer and has no easy way to get back to the owning mesh. Furthermore CustomDataAttributeProvider is also used for Curves and PointClouds, but this functionality is only needed for Mesh.
@ -1085,0 +1087,4 @@
Mesh *mesh = static_cast<Mesh *>(owner);
if ((type == CD_PROP_COLOR || type == CD_PROP_BYTE_COLOR) && !attribute_id.is_anonymous()) {
if (mesh->active_color_attribute == nullptr) {
mesh->active_color_attribute = static_cast<char *>(
Member

Shouldn't need to cast this to char *, that's the return type.

Shouldn't need to cast this to `char *`, that's the return type.
@ -1085,0 +1100,4 @@
static AttributeRemoveHandler mesh_remove_handler =
[](void *owner, AttributeIDRef const &attribute_id) -> void {
Mesh *mesh = static_cast<Mesh *>(owner);
if (mesh->active_color_attribute && !strncmp(mesh->active_color_attribute,
Member

Looks much better as StringRef(mesh->active_color_attribute) == attribute_id.name() IMO

Looks much better as `StringRef(mesh->active_color_attribute) == attribute_id.name()` IMO
@ -1085,0 +1104,4 @@
attribute_id.name().data(),
attribute_id.name().size()))
{
MEM_SAFE_FREE(mesh->active_color_attribute);
Member

So far we've decided not to remove the active name when removing the corresponding attribute. The idea is that the name might not always match an attribute on the geometry, since they might be created/set at different times. I'm not totally tied to that, but it does seem reasonable to me too.

So far we've decided not to remove the active name when removing the corresponding attribute. The idea is that the name might not always match an attribute on the geometry, since they might be created/set at different times. I'm not totally tied to that, but it does seem reasonable to me too.
Author
Member

ok, that's good I could just remove the delete handler.

ok, that's good I could just remove the delete handler.
Member

The basic idea of setting the first created color attribute active seems somewhat reasonable I guess. But the alternative is to add a "Set Active Color Attribute" node, which is probably a bit more explicit (and therefore intuitive?). The remaining question we had about that when we discussed it is what name to use. But something like "active_color" might be fine Or it could be specified too.

as it currently is there is no way to delete attributes from GN I think?

There is the "Remove Named Attribute" node.


Also, as a high level design goal, personally I think the whole concept of an active color attribute in a procedural context is more of a crutch than a design goal. It just means connections are more implicit, and means you need to keep track of even more state. But it's the only way we have to create reusable materials that use color attributes, so we're sort of stuck with it for now.

The basic idea of setting the first created color attribute active seems somewhat reasonable I guess. But the alternative is to add a "Set Active Color Attribute" node, which is probably a bit more explicit (and therefore intuitive?). The remaining question we had about that when we discussed it is what name to use. But something like "active_color" might be fine Or it could be specified too. >as it currently is there is no way to delete attributes from GN I think? There is the "Remove Named Attribute" node. --- Also, as a high level design goal, personally I think the whole concept of an active color attribute in a procedural context is more of a crutch than a design goal. It just means connections are more implicit, and means you need to keep track of even more state. But it's the only way we have to create reusable materials that use color attributes, so we're sort of stuck with it for now.
Author
Member

Creating a an Active Color node might be better/more intuitive.

Though a bit strange that an 'Active Color' node would set the 'default_color_attribute' and not the 'active_color_attribute'.

I think the whole concept of an active color attribute in a procedural context is more of a crutch than a design goal.

I don't really disagree. But there are numerous bugreports because GN behaves differently in this respect than all other modifiers.
For backwards compatibility I think it would still be nice to always set a default, even if we have an explicit node as well.

Creating a an Active Color node might be better/more intuitive. Though a bit strange that an 'Active Color' node would set the 'default_color_attribute' and not the 'active_color_attribute'. > I think the whole concept of an active color attribute in a procedural context is more of a crutch than a design goal. I don't really disagree. But there are numerous bugreports because GN behaves differently in this respect than all other modifiers. For backwards compatibility I think it would still be nice to always set a default, even if we have an explicit node as well.
Hans Goudey added this to the Nodes & Physics project 2023-11-28 21:17:39 +01:00
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Reference: blender/blender#109083
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