Geometry Nodes: support matrix socket in accumulate field node #121326

Jacques Lucke · 2024-05-02T01:19:45+02:00

Jacques Lucke commented

2024-05-02 01:19:45 +02:00

This adds support for matrices in the accumulate field node. This is quite useful to evaluate chains of parent matrices (although branching is not easily possible with this approach).

The main tricky thing here is that matrices are generally accumulated using multiplication and the order of multiplication matters. For other data types we currently always use addition. I don't have use cases for other ways to accumulate matrices right now, so maybe it's fine not to add additional options here for now.

This adds support for matrices in the accumulate field node. This is quite useful to evaluate chains of parent matrices (although branching is not easily possible with this approach). The main tricky thing here is that matrices are generally accumulated using multiplication and the order of multiplication matters. For other data types we currently always use addition. I don't have use cases for other ways to accumulate matrices right now, so maybe it's fine not to add additional options here for now. ![image](/attachments/bdd35e27-76f5-4b86-8f57-b20c677deba8) ![image](/attachments/1443aa02-9c8e-4a4a-a3b4-298c33f39571)

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2024-05-02 01-11-45.mp4

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accumulate_matrices.blend

943 KiB

Jacques Lucke added 1 commit 2024-05-02 01:19:55 +02:00

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5e05465a41 support matrix in accumulate field node

Jacques Lucke requested review from Simon Thommes 2024-05-02 01:23:19 +02:00

Jacques Lucke requested review from Hans Goudey 2024-05-02 01:23:19 +02:00

Jacques Lucke commented

2024-05-02 01:23:41 +02:00

@blender-bot build

Iliya Katushenock referenced this pull request

2024-05-02 06:18:29 +02:00

Geometry Nodes: Accumulate Field for Rotation value type #116701

Hans Goudey approved these changes 2024-05-02 20:00:41 +02:00

Hans Goudey left a comment

I think this is reasonable. The only argument against it is if we wanted to have a separate node for multiply accumulation. But that can be versioned later like you say.
We should probably support rotations here too if we support matrices.

I think this is reasonable. The only argument against it is if we wanted to have a separate node for multiply accumulation. But that can be versioned later like you say. We should probably support rotations here too if we support matrices.

Shmuel Israel commented

2024-05-07 07:17:18 +02:00

First-time contributor

I agree. Multiplication is the most useful accumulation. I actually wanted rotation (quaternion) accumulation (with quaternion multiplication) ever since we got the rotation socket. This could be very useful and make things much faster than needing to use Repeat Zone.

Simon Thommes reviewed 2024-05-08 16:37:31 +02:00

Simon Thommes left a comment

I think it's generally fine to include this multiplicative accumulation in this node, but I'm not entirely sure that accumulating Matrices implies multiplication as much as accumulating Transforms clearly does.

What about calling the enum option Transform? If we go the more generic route it seems a little arbitrary to me to opt for multiplication which we are clearly favoring due to the application for transforms specifically.

I think it's generally fine to include this multiplicative accumulation in this node, but I'm not entirely sure that accumulating Matrices implies multiplication as much as accumulating Transforms clearly does. What about calling the enum option `Transform`? If we go the more generic route it seems a little arbitrary to me to opt for multiplication which we are clearly favoring due to the application for transforms specifically.

Iliya Katushenock commented

2024-05-08 16:42:12 +02:00

Additional options make its harder to switch data type in procedural context.

Jacques Lucke commented

2024-05-08 18:24:07 +02:00

What about calling the enum option Transform?

Hmm, generally sounds reasonable, but might be a bit annoying internally.

> What about calling the enum option Transform? Hmm, generally sounds reasonable, but might be a bit annoying internally.

Jacques Lucke added 1 commit 2024-05-08 18:24:28 +02:00

12ea086017 Merge branch 'main' into accumulate-field-matrix

Hans Goudey commented

2024-05-08 18:25:38 +02:00

Rather than this intermediate method of "Transform" vs "Matrix" I'd just add the add/multiply option or figure out how that would work more generally.

Jacques Lucke commented

2024-05-08 18:28:45 +02:00

The general solution is more complex than just add/multiply because matrix multiplication is not commutative. But we could have a separate matrix accumulation mode.

Iliya Katushenock commented

2024-05-08 18:47:49 +02:00

Yeah, Multipy node with rotation, matrix, and any other type... and explicit outputs for different args order

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Geometry Nodes: support matrix socket in accumulate field node #121326

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