Procedural Grass

RedGPU.Landscape.GrassManager scatters and culls hundreds of thousands to millions of grass and vegetation clumps across the terrain around the camera in 16m cells directly in GPU compute shaders.

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1. Registering Grass Types (grassManager.addType)

Prepare a grass clump Mesh and call landscape.grassManager.addType(options) to register it. Call addType() multiple times to mix several grass varieties or wildflowers.

• Two-Sided Foliage PBR & Subsurface Scattering: Supports backlit transmission (subsurfaceStrength, subsurfaceColor) through thin blades and ground color blending (groundBlendStrength) that blends the underlying terrain color into grass roots.
• Global Wind Synchronization: Automatically animates vertex wind sway based on scene.windManager direction and speed.

new RedGPU.GLTFLoader(
    redGPUContext,
    './assets/terrain/grass.glb',
    (loader) => {
        const grass = landscape.grassManager.addType({
            name: 'Lawn Clump',
            mesh: loader.resultMesh,            // Source grass clump Mesh to instance
            densityPerHectare: 20000,           // 20,000 instances per hectare (10,000㎡)
            cullingDistance: 110,               // Maximum visible distance (110m)
            targetLayer: 'Grass',               // Spawn only on the 'Grass' terrain layer
            maxSlope: 35,                       // Spawn only on slopes up to 35 degrees
            minScale: [12.0, 8.0, 12.0],        // Minimum random scale [x, y, z]
            maxScale: [18.0, 12.0, 18.0],       // Maximum random scale [x, y, z]
            roughness: 0.55,
            subsurfaceStrength: 0.35,           // Backlit subsurface scattering (SSS) strength
            subsurfaceColor: [0.35, 0.65, 0.15],
            groundBlendStrength: 0.85,          // Root color blending strength with terrain ground (VBT)
            receiveShadow: true,
            castShadow: true
        });
    }
);

Live Example: Procedural Grass

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2. GrassOptions Key Properties

Category	Property	Default	Description
Identity & Mesh	name	Required	Unique identifier name for the grass type
	mesh	Required	Source Mesh instance from which grass geometry and default textures are extracted
	baseColorTexture	From mesh material	Grass base color texture path or BitmapTexture
Density & Culling	densityPerHectare	5000.0	Baseline placement density per hectare (10,000㎡)
	densityMultiplier	1.0	Real-time multiplier applied to the baseline density
	cullingDistance	100.0	Maximum camera distance at which grass is rendered (with automatic distance scale fade-out)
	targetLayer	''	Name or index of the LandscapeLayer referenced for placement density
Transform & Slope	minSlope / maxSlope	0.0 / 35.0	Minimum and maximum terrain slope angles allowed for growth (in degrees)
	minScale / maxScale	[0.7, 0.7] / [1.3, 1.4]	Per-instance random scale range ([width, height] or [x, y, z])
	bottomOffset	0.0	Vertical (Y) offset relative to the terrain surface
Material & PBR	alphaCutoff	0.2	Texture alpha mask cutoff threshold (0.01 ~ 1.0)
	roughness	0.55	Grass surface roughness (0.04 ~ 1.0)
	subsurfaceStrength	0.25	Backlit subsurface scattering intensity (0.0 ~ 3.0)
	subsurfaceColor	[0.35, 0.65, 0.15]	Subsurface scattering RGB color (0.0 ~ 1.0)
	exposureBoost	1.0	Brightness exposure boost multiplier
	groundBlendStrength	1.0	Bottom blending strength with terrain ground color (VBT) and normal (0.0 ~ 1.0)
Shadows	receiveShadow / castShadow	true / true	Enables shadow receiving and casting
	shadowStrength	1.0	Darkness strength of received shadows (0.0 ~ 1.0)

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Related Examples

• Procedural Grass
• Open World Integration

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Next Step: Learn Foliage & Impostors