The document discusses techniques for generating undergrowth in game environments using cellular noise. It describes using a 3x64x64 texture atlas of alpha masks for undergrowth placed in 16x16m grid cells on the CPU and instantiated on the GPU. Normal maps are also generated to add detail to undergrowth. Care for anti-aliasing shaders is mentioned to improve the appearance of undergrowth edges.

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5. Xbox 360 & PS3

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float3 filterNormal(float2 uv, float texelSize, float texelAspect)
{
float4 h;
h[0] = hmap.Sample(bilSampler, uv + texelSize*float2( 0,-1)).r;
h[1] = hmap.Sample(bilSampler, uv + texelSize*float2(-1, 0)).r;
h[2] = hmap.Sample(bilSampler, uv + texelSize*float2( 1, 0)).r;
h[3] = hmap.Sample(bilSampler, uv + texelSize*float2( 0, 1)).r;
float3 n;
n.z = (h[0] - h[3]) * texelAspect;
n.x = (h[1] - h[2]) * texelAspect;
n.y = 2;
return normalize(n);
}

28. Photoshop Overlay blend
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float overlayBlend(float base, float value, float opacity)
{
float a = base < 0.5 ? 2*base*value : 1 - 2*(1-base)*(1-value);
return lerp(base, a, opacity);
}

43. UndergrowthϵͳЧ¹û
No undergrowth With undergrowth

45. 16x16m cell
cells

46. UndergrowthϵͳÄʱ´ú
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Generated mask
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Normalmap

51. More care for shader antialiasing

52. Battlefield
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