Attributes¶

Attributes are data attached to your geometry. They're the secret to data-driven procedural modeling - enabling selections, coloring, and advanced workflows.

What are Attributes?¶

Attributes store information on geometry components:

Vertex (Point)  → Point Attributes   (position, color, normal, ...)
Face (Triangle) → Face Attributes    (material ID, ...)
Mesh (Object)   → Primitive Attribs  (name, layer, ...)

Think of them as spreadsheet data attached to your 3D geometry.

Built-in Attributes¶

Nodo automatically creates some attributes:

Point Attributes¶

Name	Type	Description
`P`	vector3	Position (x, y, z)
`N`	vector3	Normal vector
`Cd`	vector3	Color (RGB, 0-1 range)
`uv`	vector2	Texture coordinates
`id`	int	Vertex ID/index

Access in expressions:

@P       # Position vector
@P.x     # X coordinate
@P.y     # Y coordinate
@P.z     # Z coordinate
@N       # Normal
@Cd      # Color

Face Attributes¶

Name	Type	Description
`materialid`	int	Material assignment
`N`	vector3	Face normal

Primitive Attributes¶

Name	Type	Description
`name`	string	Object name

Creating Attributes¶

Use the Attribute Create node to add custom attributes.

Example: Height Attribute¶

Goal: Store Y-position for each vertex

Setup:

Sphere
  ↓
Attribute Create
  - Name: "height"
  - Type: Float
  - Value: @P.y

Result: Each vertex has a height attribute = its Y coordinate

Use: - Select high vertices: @height > 0.5 - Color by height: @Cd = [@height, 0, 0]

Attribute Types¶

Float¶

Single decimal number:

@height = 1.5
@temperature = 37.2
@weight = 0.8

Int¶

Whole number:

@id = 42
@material = 3
@group_id = 1

Vector2¶

Two floats (UV coordinates):

@uv = [0.5, 0.75]

Vector3¶

Three floats (positions, colors, normals):

@P = [1.0, 2.0, 3.0]
@Cd = [1.0, 0.0, 0.0]  # Red
@N = [0.0, 1.0, 0.0]   # Up

String¶

Text:

@name = "pillar_base"
@material_name = "brick"

Using Attributes¶

1. Selection (Groups)¶

Select geometry based on attribute values:

Group Node:
- Mode: Expression
- Expression: @P.y > 0.5

Result: Select all vertices above Y=0.5

2. Color¶

Set vertex colors procedurally:

Attribute Create:
- Name: Cd
- Type: Vector3
- Value: [@P.x, @P.y, 0]

Result: Color based on position (red = X, green = Y)

3. Conditional Operations¶

Use attributes to drive operations:

Delete faces where @materialid == 2
Extrude faces where @selected == 1

4. Data-Driven Deformations¶

Example: Twist based on height

Attribute Create:
- Name: twist_amount
- Value: @P.y * 45

Then in Twist node:
- Angle: ch("@twist_amount")

Common Workflows¶

Color Gradient by Height¶

1. Sphere
2. Attribute Create:
   Name: Cd
   Type: Vector3
   Value: [0, @P.y + 0.5, 0]

Result: Green gradient (dark bottom, bright top)

Random Colors¶

1. Box
2. Attribute Create:
   Name: Cd
   Type: Vector3
   Value: [rand(@id), rand(@id+1), rand(@id+2)]

Result: Each vertex has random color

Material ID by Position¶

1. Cylinder
2. Attribute Create:
   Name: materialid
   Type: Int
   Value: @P.y > 0 ? 1 : 2

Result: Top half = material 1, bottom = material 2

Distance from Center¶

1. Grid
2. Attribute Create:
   Name: dist
   Type: Float
   Value: length(@P)

Result: Each point stores distance from origin

Attribute Interpolation¶

When geometry changes, attributes can be interpolated:

Subdivide¶

Vertex A: @height = 0.0
Vertex B: @height = 1.0

After subdivide:
New vertex (midpoint): @height = 0.5 (interpolated)

Attributes blend smoothly across new geometry.

Merge¶

Mesh A vertices: @id = 0, 1, 2, ...
Mesh B vertices: @id = 0, 1, 2, ...

After merge:
Combined: @id renumbered to avoid conflicts

Attribute Promotion¶

Convert between attribute classes:

Point → Face¶

Average point values for each face:

3 vertices with @height = [0.5, 0.6, 0.7]
Face @height = (0.5 + 0.6 + 0.7) / 3 = 0.6

Face → Point¶

Distribute face values to points:

Face @material = 2
All 3 vertices get @material = 2

Use Case: Material IDs, selections

Deleting Attributes¶

Use Attribute Delete node to remove unneeded attributes:

Attribute Delete:
- Name: "temp_*"  (wildcard pattern)
- or specific: "old_color", "scratch_data"

Why delete? - Reduce memory usage - Clean up temporary data - Prepare for export

Expressions with Attributes¶

Reading Attributes¶

@P.y               # Current point's Y position
@Cd.r              # Red component of color
@N                 # Normal vector
@id                # Vertex ID

Writing Attributes¶

@Cd = [1, 0, 0]           # Set red
@height = @P.y * 2        # Double Y position
@active = @P.y > 0 ? 1 : 0  # Boolean flag

Math on Attributes¶

@dist = length(@P)               # Distance from origin
@normalized_height = @P.y / 10   # Normalize
@sum = @val1 + @val2             # Combine values

Conditionals¶

@result = @value > 0.5 ? 1 : 0
@color = @hot ? [1,0,0] : [0,0,1]  # Red if hot, blue if cold

Advanced Patterns¶

Checkerboard Pattern¶

Attribute Create:
- Name: checker
- Value: (floor(@P.x) + floor(@P.z)) % 2
- Then use for color:
  @Cd = @checker == 0 ? [1,1,1] : [0,0,0]

Radial Gradient¶

Attribute Create:
- Name: radial
- Value: length([@ P.x, @P.z])
- Then:
  @Cd = [1 - @radial, @radial, 0]

Selection Mask¶

Attribute Create:
- Name: mask
- Value: sin(@P.x * 3.14) > 0 ? 1 : 0

Group (Expression): @mask == 1
Group Delete: Removes masked areas

Instance ID¶

After Copy to Points:
Each instance gets @instanceid

Use for variation:
@Cd = [@instanceid * 0.1, 0, 0]

Attribute Scope¶

Point Attributes¶

Stored per vertex
Most common type
Used for: positions, colors, normals, UVs

Example:

1000 vertex mesh
@Cd attribute = 1000 color values (one per vertex)

Face Attributes¶

Stored per triangle
Less common
Used for: material IDs, face selections

Example:

500 triangle mesh
@materialid = 500 integer values (one per face)

Vertex Attributes¶

Same as point attributes in Nodo
Terminology varies by software

Best Practices¶

1. Name Attributes Clearly¶

✅ @selection_mask, @height_normalized, @color_gradient
❌ @x, @temp, @thing

2. Clean Up Temporary Attributes¶

After using @temp_dist for calculation:
→ Attribute Delete: temp_*

3. Use Standard Names¶

Follow conventions:

@Cd   for color (not @color, @rgb)
@N    for normal (not @norm)
@uv   for texture coords

4. Check Attribute Type¶

Float: Single values (height, weight, temperature)
Vector3: Positions, colors, normals
Int: IDs, indices, material numbers

5. Scope Awareness¶

Point attributes: Per-vertex data (most common)
Face attributes: Per-triangle data (materials, selections)

Troubleshooting¶

Attribute Not Found¶

Error: @myattr doesn't exist

Fix: - Check spelling (case-sensitive!) - Verify Attribute Create node executed - Check attribute was created on points (not faces)

Wrong Data Type¶

Error: Assigning vector to float attribute

Fix: - Match types: Float = scalar, Vector3 = [x,y,z] - Convert if needed: length(@P) (vector → float)

Attribute Not Updating¶

Cause: Node not re-executing

Fix: - Change a parameter to force update - Check node connections - Verify expression mode enabled

Colors Not Showing¶

Cause: @Cd attribute missing or wrong range

Fix: - Ensure @Cd is Vector3 - Values must be 0.0 to 1.0 range - Enable vertex colors in viewport

Performance Tips¶

Minimize Attributes¶

Only create what you need:

❌ 20 temporary attributes
✅ 3 essential attributes + delete temps

Batch Operations¶

✅ One Attribute Create with multiple attributes
❌ 10 separate Attribute Create nodes

Optimize Expressions¶

✅ @dist = length(@P)  (calculated once)
❌ Multiple uses of length(@P)  (calculated each time)

Examples¶

Rainbow Colors¶

Grid (10×10)
  ↓
Attribute Create:
  Name: Cd
  Type: Vector3
  Value: [(sin(@id * 0.5) + 1) * 0.5,
          (cos(@id * 0.3) + 1) * 0.5,
          (sin(@id * 0.7) + 1) * 0.5]

Height-Based Selection¶

Cylinder
  ↓
Group:
  Mode: Expression
  Expression: @P.y > 0.5
  ↓
Group Delete (delete selected = top half removed)

Distance Falloff¶

Sphere
  ↓
Attribute Create:
  Name: falloff
  Value: 1.0 - min(length(@P) / 2.0, 1.0)
  ↓
Attribute Create:
  Name: Cd
  Value: [@falloff, @falloff, @falloff]

Result: White center, black edges

Next Steps¶

Understand Groups - Groups
Use in Workflows - Procedural Patterns
Expression System - Expression Syntax
Node Reference - Attribute Create

Key Takeaways¶

✅ Attributes = Data attached to geometry components ✅ Types = Float, Int, Vector⅔, String ✅ Scope = Point (vertex), Face (triangle), Primitive (object) ✅ Built-ins = @P, @N, @Cd, @uv, @id ✅ Uses = Selection, coloring, data-driven operations ✅ Access = @attribute_name in expressions

Remember: Attributes turn geometry into data - enabling procedural magic!