Experimental: This Feature is currently experimental and is subject to change in later major versions.
Set Position (Mesh)
Menu Path : Position > Set Position (Mesh)
Menu Path : Position > Set Position (Skinned Mesh)
The Set Position (Mesh) Block calculates a position based on mesh vertex data and stores the result in the position attribute, based on composition.
This Block also calculates a direction vector based on the mesh normal, and stores it to the direction attribute, based on composition.
Note: Velocity from Direction and Speed Blocks can then process the direction attribute.
Block compatibility
This Block is compatible with the following Contexts:
- Initialize
- Update
- Any output Context
Block settings
| Setting | Type | Description |
|---|---|---|
| Spawn Mode | Enum | Specifies how to distribute particles within the mesh. The options are: • Random: Calculates a per-particle random progress uniform sampling among the chosen primitive in Placement Mode. • Custom: Allows you to manually specify the sampling parameters. |
| Placement mode | Enum | Specifies which primitive part of the mesh to sample from: • Vertex: Samples positions from all listed vertices. • Edge: Samples from an interpolation between two consecutives vertices that are part of a triangle on the mesh. • Surface: Samples from an interpolation between three vertices that define a triangle on the mesh. |
| Surface coordinates | Enum | Specifies the method this Block uses to sample the surface of a triangle. • Barycentric: Samples the surface using raw barycentric coordinates. Using this method, sampled positions are not constrained by the triangle edges which is useful if you have baked a position outside of the Visual Effect Graph. • Uniform: Samples the surface uniformly within the triangle area. This property only appears if you set Placement mode to Surface and Spawn Mode to Custom. |
| Source | Enum | (Inspector) Specifies the kind of geometry to sample from. The options are: • Mesh: Samples from a mesh asset. • Skinned Mesh Renderer: Samples from a Skinned Mesh Renderer. |
| Composition Position | Enum | (Inspector) Specifies how this Block composes the position attribute. The options are: • Set: Overwrites the position attribute with the new value. • Add: Adds the new value to the position attribute value. • Multiply: Multiplies the position attribute value by the new value. • Blend: Interpolates between the position attribute value and the new value. You can specify the blend factor between 0 and 1. |
| Composition Direction | Enum | (Inspector) Specifies how this Block composes the direction attribute. The options are: • Set: Overwrites the position attribute with the new value. • Add: Adds the new value to the position attribute value. • Multiply: Multiplies the position attribute value by the new value. • Blend: Interpolates between the position attribute value and the new value. You can specify the blend factor between 0 and 1. |
Block properties
| Input | Type | Description |
|---|---|---|
| Mesh | Mesh | The source mesh asset to sample. This property only appears if you set Source to Mesh. |
| Skinned Mesh Renderer | Skinned Mesh Renderer | The source Skinned Mesh Renderer component to sample. This is a reference to a component within the scene. To assign a Skinned Mesh Renderer to this port, create a Skinned Mesh Renderer property in the Blackboard and expose it. This property only appears if you set Source to Skinned Mesh Renderer. |
| Vertex | uint | The index of the vertex to sample. This property only appears if you set Placement mode to Vertex and Spawn Mode to Custom. |
| Index | uint | The start index of the edge to sample from. The Block uses this index and the following index to select the line to sample from. This property only appears if you set Placement mode to Edge and Spawn Mode to Custom. |
| Triangle | uint | The index of triangle to sample, assuming the index buffer contains a triangle list. This property only appears if you set Placement mode to Surface, Spawn Mode to Custom, and Spawn Mode to Custom. |
| Edge | float | The interpolation value the Block uses to sample along the edge. This is the percentage along the edge, from start position to end position, that the sample position is taken. This property only appears if you set Placement mode to Edge and Spawn Mode to Custom. |
| Barycentric | Vector2 | The raw barycentric coordinate to sample from the triangle at. The input is two-dimensional (X and Y) and the block calculates the Z value using the values you input: Z = 1 - X - Y. This sampling method does not constrain the sampled position inside the triangle edges. This property only appears if you set Placement mode to Surface, Surface coordinates to Barycentric, and Spawn Mode to Custom. |
| Square | Vector2 | The uniform coordinate to sample the triangle at. The Block takes this value and maps it from a square coordinate to triangle space. To do this, it uses the method outline in the paper A Low-Distortion Map Between Triangle and Square (Heitz 2019). This property only appears if you set Placement mode to Surface, Surface coordinates to Uniform, and Spawn Mode to Custom. |
| Blend Position | Float | The blend percentage between the current position attribute value and the newly calculated position value. This property only appears if you set Composition Position to Blend. |
| Blend Direction | Float | The blend percentage between the current direction attribute value and the newly calculated direction value. This property only appears if you set Composition Direction to Blend. |
Limitations
The Mesh sampling feature has the following limitations:
- It only supports VertexAttributeFormat.Float32 for all VertexAttributes except Color, which has to be a four component attribute using either VertexAttributeFormat.UInt8 or VertexAttributeFormat.Float32 format.
- If a Mesh is not readable, the Position (Mesh) Block and Sample Mesh Operator return zero values when they attempt to sample from it. For information on how to make a Mesh readable, see Model import settings.
Reference list
- Heitz, Eric. 2019. "A Low-Distortion Map Between Triangle and Square". hal-02073696v2