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$$ \Large\textbf{Attributes are how Houdini gives meaning to geometry.} $$
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Learn about attributes: 1. Oversimplified Attributes — The Data 🟢
| Data Type | VEX Attribute Syntax | What it stores | Example | Common Use |
|---|---|---|---|---|
Integer — int |
i@name |
A whole number | i@id = 1; |
IDs, counts, flags |
Float — float |
f@name |
A floating-point number | f@weight = 1.5; |
Weights, scale, values |
Vector — vector |
v@name |
Three components: {x, y, z} |
v@dir = set(1, 0, 0); |
Positions, directions, colors |
Vector4 — vector4 |
No dedicated standard vector4 attribute binding equivalent to v@ |
Four components: {x, y, z, w} |
vector4 value = {0, 0, 0, 1}; |
Four-component data |
Quaternion — vector4 representation |
p@name |
A rotation represented by four components | p@orient = quaternion(radians(45), {0, 1, 0}); |
Orientations, rotations |
Matrix3 — matrix3 |
3@name |
A 3×3 matrix | 3@transform = ident(); |
Rotation and linear transforms |
Matrix — matrix |
4@name |
A 4×4 matrix | 4@transform = ident(); |
Full transforms, including translation |
String — string |
s@name |
Text | s@name = "Hello"; |
Names, paths, tags |
Integer array — int[] |
i[]@name |
Multiple integers | i[]@ids = array(1, 2, 3); |
Lists of IDs |
Float array — float[] |
f[]@name |
Multiple floats | f[]@values = array(1.0, 2.0, 3.0); |
Weights, samples, values |
Vector array — vector[] |
v[]@name |
Multiple vectors | v[]@positions = array(set(0,0,0), set(1,0,0)); |
Positions, directions |
String array — string[] |
s[]@name |
Multiple strings | s[]@tags = array("apple", "banana", "orange"); |
Paths, tags, identifiers |
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$$ \Large\textbf{Type} \;\rightarrow\; \textbf{What kind of data is it?} $$
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attribute_general_gerardojustel_re1mon_red.mp4
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$$ \Large\textbf{Class} \;\rightarrow\; \textbf{What geometry element does the data belong to?} $$
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An attribute is data attached to geometry.
Attributes aren't necessarily visible geometry. They're information about the geometry.
@Cd → color
@pscale → size
@v → velocity
@N → direction
@id → identity
@orient → rotation
Attributes are how you store information and use that information to control what Houdini does.
A point isn't just a point. With attributes, it can become:
**A particle moving at 5 m/s, rotated 30°, colored red, scaled to 0.2, and carrying ID 1847.**
$$ \textbf{Create data} \;\rightarrow\; \textbf{Store it as attributes} \;\rightarrow\; \textbf{Use that data to drive behavior.} $$
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$$ \Large\textbf{Attribute Types} $$
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Integer — int
Whole numbers:
$$ 1,\ 2, \ 3 $$
Float — float
Decimal numbers:
$$ 0.5,\ 3.14 $$
Vector — vector
Three floats:
$$ \{x, y, z\} $$
Vector4 — vector4
Four floats.
Commonly used for quaternions.
$$ \{x, y, z, w\} $$
Matrix3 — matrix3
A 3×3 matrix.
Commonly used for rotations and transforms.
$$ \begin{bmatrix}a & b & c \\d & e & f \\g & h & i\end{bmatrix} $$
Matrix — matrix
A 4×4 matrix.
Commonly used for full transforms.
$$ \begin{bmatrix}a & b & c & d \\e & f & g & h \\i & j & k & l \\m & n & o & p\end{bmatrix} $$
String — string
Text data.
$$ Hello $$
f[] i[] v[]Arrays allow an attribute to contain multiple values.
Integer, Float, Vector arrays
$$ \{x_1, x_2, x_3, \ldots, x_n\} $$
s[]Useful for storing multiple pieces of text such as paths, tags, or other identifiers.
$$ \{\text{"apple"},\ \text{"banana"},\ \text{"orange"}\} $$
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