Geometry Nodes: porting the VertexWeightProximity modifier #84842

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Victor-Louis De Gusseme · 2021-01-18T22:14:04+01:00

2021-01-18 22:14:04 +01:00

This task covers the design of how the functionality of the VertexWeightProximity modifier could be ported to geometry nodes.

I've started implementing an Attribute Proximity node here: https://developer.blender.org/D10154

VertexWeightProximity modifier

The VertexWeightProximity modifier sets the weights of vertex group based on the distance of each vertex to a Target Object. The distances are mapped to values in the 0 to 1 range.

The main code for this modifier can be found in blender/source/blender/modifiers/intern/MOD_weightvgproximity.c. The distance calculations are done using a BVH.

Use Cases

Among other things, something users will definitely want to do is:

Create a scene with some objects
Scatter points/objects in the remaining free space

In this video Miro Horvath shows a nice example: scattering trees in a landscape, but not on a road and a river in the landscape. He achieves this by using VertexWeightProximity to create vertex weights that are 0 around the road and river, and then feeding these vertex weights to the Point Distribute Node. Below are screenshots of his vertex weights and his result:

What's nice about this workflow is that he can move the river around and the trees will appear/disappear as needed.

Design for Geometry Nodes

In the spirit to keep geometry nodes atomic, it probably makes sense to strip away most of the options in the VertexWeightProximity modifier. All the mapping functionality (falloff, lowest, highest, normalize) and masking functionality (the stuff in 'Influence') could be done by other nodes. The geometry nodes should thus basically calculate and output distances. The node could look something like this:

Attribute Proximity Node

So how it would work is that the node would output for each vertex in the first geometry, the distance to the closest point on the second geometry.
Suggestions for better names for the inputs are welcome, maybe Geometry and Target Geometry?

Miro's workflow could then be simplified to something like this:

Add geometry nodes modifier to the landscape
Read road geometry with an Object Info node
Use proximity node to calculate a vertex proximities between the landscape and the road
Map the proximities to a 0->1 range with other nodes

Scatter on landscape with the values from the previous step as density attribute

Notes

In general I think a "procedural vertex weights" workflow will be essential for geometry nodes, but we should also think how about the trade offs between a texture driven/vertex weights driven workflow. One thing that comes to mind is that increasing the resolution of vertex weights requires you to add additional vertices that are not needed from a modelling perspective. This might be a problem for controlling scattering on low-poly meshes.
I can't figure out how to visualize vertex weights in Object mode. It would be very useful to be able to move a target object around and see the effect on the vertex weights.

This task covers the design of how the functionality of the VertexWeightProximity modifier could be ported to geometry nodes. I've started implementing an Attribute Proximity node here: https://developer.blender.org/D10154 VertexWeightProximity modifier **** The VertexWeightProximity modifier sets the weights of vertex group based on the distance of each vertex to a Target Object. The distances are mapped to values in the 0 to 1 range. ![vertex_weight_proximity.png](https://archive.blender.org/developer/F9585964/vertex_weight_proximity.png) The main code for this modifier can be found in `blender/source/blender/modifiers/intern/MOD_weightvgproximity.c`. The distance calculations are done using a BVH. Use Cases **** Among other things, something users will definitely want to do is: - Create a scene with some objects - Scatter points/objects in the remaining free space In this [video ](https://www.youtube.com/watch?v=rd5joo1aKmk) Miro Horvath shows a nice example: scattering trees in a landscape, but not on a road and a river in the landscape. He achieves this by using VertexWeightProximity to create vertex weights that are 0 around the road and river, and then feeding these vertex weights to the Point Distribute Node. Below are screenshots of his vertex weights and his result: ![river.png](https://archive.blender.org/developer/F9586117/river.png) ![result.png](https://archive.blender.org/developer/F9586119/result.png) What's nice about this workflow is that he can move the river around and the trees will appear/disappear as needed. Design for Geometry Nodes **** In the spirit to keep geometry nodes atomic, it probably makes sense to strip away most of the options in the VertexWeightProximity modifier. All the mapping functionality (falloff, lowest, highest, normalize) and masking functionality (the stuff in 'Influence') could be done by other nodes. The geometry nodes should thus basically calculate and output distances. The node could look something like this: Attribute Proximity Node -------------------------------- ![attr_proximity.png](https://archive.blender.org/developer/F9588156/attr_proximity.png) So how it would work is that the node would output for each vertex in the first geometry, the distance to the closest point on the second geometry. Suggestions for better names for the inputs are welcome, maybe `Geometry` and `Target Geometry`? Miro's workflow could then be simplified to something like this: - Add geometry nodes modifier to the landscape - Read road geometry with an Object Info node - Use proximity node to calculate a vertex proximities between the landscape and the road - Map the proximities to a 0->1 range with other nodes # Scatter on landscape with the values from the previous step as density attribute Notes **** - In general I think a "procedural vertex weights" workflow will be essential for geometry nodes, but we should also think how about the trade offs between a texture driven/vertex weights driven workflow. One thing that comes to mind is that increasing the resolution of vertex weights requires you to add additional vertices that are not needed from a modelling perspective. This might be a problem for controlling scattering on low-poly meshes. - I can't figure out how to visualize vertex weights in Object mode. It would be very useful to be able to move a target object around and see the effect on the vertex weights.

Victor-Louis De Gusseme commented

2021-01-18 22:14:04 +01:00

Added subscriber: @victorlouis

Dimitri Bastos commented

2021-01-19 02:48:28 +01:00

Added subscriber: @DimitriBastos

Dimitri Bastos commented

2021-01-19 02:48:28 +01:00

Is it possible to not be totally vertex dependent on those effects?

EDIT for clarity:

For instance, we can create weights by using an empty or another mesh, but it would be nice to create weights using a parametric workflow not mesh dependent like using a curve, or like using some sort of linear object (similar to the weight gradient tool). For what I know, the Weight Proximity Modifier is based on object origin, so even if you use a curve it will only read the curve origin, not the curve points or the curve geometry.

Is it possible to not be totally vertex dependent on those effects? EDIT for clarity: For instance, we can create weights by using an empty or another mesh, but it would be nice to create weights using a parametric workflow not mesh dependent like using a curve, or like using some sort of linear object (similar to the weight gradient tool). For what I know, the Weight Proximity Modifier is based on object origin, so even if you use a curve it will only read the curve origin, not the curve points or the curve geometry.

Victor-Louis De Gusseme commented

2021-01-19 09:32:43 +01:00

You mean working texture based? I'm not sure what the current plan is for integration of textures and geometry nodes. I think there's some complexities with integrating textures that aren't there for vertex weights, so using vertex weights is just a start.

Miro Horváth commented

2021-01-19 10:15:01 +01:00

Added subscriber: @MiroHorvath

Dimitri Bastos commented

2021-01-19 15:04:22 +01:00

In #84842#1096268, @victorlouis wrote:
You mean working texture based? I'm not sure what the current plan is for integration of textures and geometry nodes. I think there's some complexities with integrating textures that aren't there for vertex weights, so using vertex weights is just a start.

Not exactly using textures. I think I'm not making myself clear, sorry. What probably I want to say is if there is a way to add more shapes for creating weights.

For instance, we can create weights by using an empty or another mesh, but it would be nice to create weights using a parametric workflow not mesh dependent like using a curve, or like using some sort of linear object (similar to the weight gradient tool). . For what I know, the Weight Proximity Modifier is based on object origin, so even if you use a curve it will only read the curve origin, not the curve points or the curve geometry.

> In #84842#1096268, @victorlouis wrote: > You mean working texture based? I'm not sure what the current plan is for integration of textures and geometry nodes. I think there's some complexities with integrating textures that aren't there for vertex weights, so using vertex weights is just a start. Not exactly using textures. I think I'm not making myself clear, sorry. What probably I want to say is if there is a way to add more shapes for creating weights. For instance, we can create weights by using an empty or another mesh, but it would be nice to create weights using a parametric workflow not mesh dependent like using a curve, or like using some sort of linear object (similar to the weight gradient tool). . For what I know, the Weight Proximity Modifier is based on object origin, so even if you use a curve it will only read the curve origin, not the curve points or the curve geometry.

Victor-Louis De Gusseme commented

2021-01-19 16:37:47 +01:00

I think current modifier can already do a few things you describe by choosing Proximity Mode Geometry. But indeed, the goal is that distances are calculated to all sorts of geometry, meshes, point clouds, curves etc. I'm not sure how hard supporting curves would be, maybe as a first version curves could be converted to a set of edges.

I think current modifier can already do a few things you describe by choosing Proximity Mode `Geometry`. But indeed, the goal is that distances are calculated to all sorts of geometry, meshes, point clouds, curves etc. I'm not sure how hard supporting curves would be, maybe as a first version curves could be converted to a set of edges.

blender-admin commented

2021-02-05 15:28:31 +01:00

This issue was referenced by 4d39a0f8eb

This issue was referenced by 4d39a0f8eb1103aa58611fff7219f4bf3d70f70f

Dalai Felinto commented

2021-02-05 16:30:46 +01:00

Changed status from 'Needs Triage' to: 'Resolved'

Dalai Felinto closed this issue

2021-02-05 16:30:46 +01:00

Dalai Felinto self-assigned this 2021-02-05 16:30:46 +01:00

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Geometry Nodes: porting the VertexWeightProximity modifier #84842

Attribute Proximity Node

Scatter on landscape with the values from the previous step as density attribute