A port of the "Bumped Lightmapped Diffuse" shader in Source Engine

BumpedLightmappedDiffuse

// ----------------------------------------
// Source Engine Bumped Lightmapped Diffuse

// Replace all values in full captials (not vertex semantics) with constants from the renderer
// Replace all functions in full captials with equivalent samplers

VertexInput
{
	float3 position    : POSITION;
	float3 normal      : NORMAL;
	float3 tangent     : TANGENT; // Every other engines ive used takes vec4 tangents from the mesh
	float4 texcoord    : TEXCOORD0;
	float2 lightmapUV0 : TEXCOORD1;
	float2 lightmapUV1 : TEXCOORD2;
};

VertexOutput
{
	float4 positionCS;
	float2 uv;
	float3 normalWS;
	float3 positionWS;
	float3 tangentWS;
	float3 bitangentWS;
	float4 lightmap01UV;
	float2 lightmap2UV;
};

VertexOutput vs (VertexInput i)
{
	VertexOutput o;
	
	o.positionWS = mul(i.position, MODEL_MATRIX);
	o.positionCS = mul(o.positionWS, VIEW_PROJECTION_MATRIX);
	o.uv = i.texcoord;
	o.normalWS = normalize(mul(i.normal, MODEL_MATRIX));
	o.tangentWS = normalize(mul(i.tangent.xyz, MODEL_MATRIX));
	o.bitangentWS = cross(o.tangentWS, o.normalWS); // Every other engine I've used divides this result by i.tangent.w
	float2 lm1 = = i.lightmapUV0 + i.lightmapUV1;
	float2 lm2 = lm1 + i.lightmapUV1;
	o.lightmap01UV = float4(lm1.xy, lm2.xy);
	o.lightmap2UV = lm2 + i.lightmapUV1;
}

float4 ps (VertexOutput IN)
{
	// Sample normal
	float3 nrm = SAMPLE_TEXTURE(NORMAL_TEXTURE, IN.uv);
	nrm = nrm * 2 - 1;
	
	// Bump basis
	float3 basisX = dot(nrm, BUMP_BASIS.x);
	float3 basisY = dot(nrm, BUMP_BASIS.y);
	float3 basisZ = dot(nrm, BUMP_BASIS.z);
	float3 basis = saturate(float3(basisX, basisY, basisZ));
	basis = basis * basis;
	
	// Sample lightmaps
	float3 lm0 = SAMPLE_TEXTURE(LIGHTMAP_TEXTURE, IN.lightmap01UV.xy) * basis.x;
	float3 lm1 = SAMPLE_TEXTURE(LIGHTMAP_TEXTURE, IN.lightmap01UV.zw) * basis.y;
	float3 lm2 = SAMPLE_TEXTURE(LIGHTMAP_TEXTURE, IN.lightmap01UV.xy) * basis.z;
	float lmScale = LIGHTMAPSCALE / (dot(basis, 1);
	float3 lmFinal = (lm0 + lm1 + lm2) * lmScale;
	
	// Sample Color
	float3 albedo = SAMPLE_TEXTURE(ALBEDO_TEXTURE, IN.uv);
	
	// Fianl
	float fogFactor = saturate(max(-(IN.positionCS.z), 0) * (-1/FARCLIP) + (FARCLIP/FARCLIP));
	float3 color = lerp(FOG_COLOR, color, fogFactor) * lmFinal;
	return color;
}