houdini-procedural-generation

houdini-procedural-generation

Version: 1.1.0 Last Updated: 2026-10-09 Dependencies: Houdini 20+

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CRITICAL: MANDATORY FIRST STEP

ALWAYS verify geometry inputs before procedural operations:

// In Attribute Wrangle before scatter/copy operations
// Check geometry validity
int pt_count = npoints(0);
int prim_count = nprims(0);

printf("Input geometry: %d points, %d primitives\n", pt_count, prim_count);

// Verify normals exist (required for orientation)
if (!hasattrib(0, "point", "N")) {
    printf("WARNING: Missing normals - add Point/Primitive Normal SOP\n");
}

Why Critical:

• Empty Geometry: Scatter/copy on empty geometry produces no output
• Missing Normals: Copy to Points without normals = no orientation control
• Scale Issues: Geometry too large/small affects scatter density and distribution

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QUICK START

Most Common Use Case: Scatter and Copy Instances

Goal: Scatter points on surface and copy geometry to those points

Step 1: Create Base Surface

Grid SOP (or any surface geometry)
- Rows: 50
- Columns: 50
- Size: 10x10

Step 2: Scatter Points

Scatter SOP 2.0
- Input: Grid
- Total Count: 1000
- Relax Iterations: 10 (distributes evenly)
- Generate Normals: ON

Step 3: Create Instance Geometry

Box SOP (or custom geometry to copy)
- Size: 0.5, 0.5, 0.5
- Center: 0, 0.25, 0 (pivot at bottom)

Step 4: Copy to Points

Copy to Points SOP
- Target Points (Left Input): Scatter output
- Source Geometry (Right Input): Box
- Attributes:
  - scale: Vary size (create f@scale on scatter points)
  - orient: Control rotation (p@orient quaternion)

Step 5: Add Variation

// On scatter points (Attribute Wrangle before Copy to Points)
// Random scale
f@scale = fit01(rand(@ptnum), 0.5, 1.5);

// Random Y rotation
vector axis = {0, 1, 0};
float angle = rand(@ptnum + 123) * 360;
p@orient = quaternion(radians(angle), axis);

// Random color (transferred to copies)
@Cd = rand(@ptnum + 456);