vec3 GetAmbient(float zonePos)
{
    return cAmbientStartColor + zonePos * cAmbientEndColor;
}

#ifdef NUMVERTEXLIGHTS
float GetVertexLight(int index, vec3 worldPos, vec3 normal)
{
    vec3 lightDir = cVertexLights[index * 3 + 1].xyz;
    vec3 lightPos = cVertexLights[index * 3 + 2].xyz;
    float invRange = cVertexLights[index * 3].w;
    float cutoff = cVertexLights[index * 3 + 1].w;
    float invCutoff = cVertexLights[index * 3 + 2].w;

    // Directional light
    #ifndef BILLBOARD
        if (invRange == 0.0)
        {
            float NdotL = max(dot(normal, lightDir), 0.0);
            return NdotL;
        }
        // Point/spot light
        else
        {
            vec3 lightVec = (lightPos - worldPos) * invRange;
            float lightDist = length(lightVec);
            vec3 localDir = lightVec / lightDist;
            float NdotL = max(dot(normal, localDir), 0.0);
            float atten = clamp(1.0 - lightDist * lightDist, 0.0, 1.0);
            float spotEffect = dot(localDir, lightDir);
            float spotAtten = clamp((spotEffect - cutoff) * invCutoff, 0.0, 1.0);
            return NdotL * atten * spotAtten;
        }
    #else
        if (invRange == 0.0)
            return 1.0;
        // Point/spot light
        else
        {
            vec3 lightVec = (lightPos - worldPos) * invRange;
            float lightDist = length(lightVec);
            vec3 localDir = lightVec / lightDist;
            float atten = clamp(1.0 - lightDist * lightDist, 0.0, 1.0);
            float spotEffect = dot(localDir, lightDir);
            float spotAtten = clamp((spotEffect - cutoff) * invCutoff, 0.0, 1.0);
            return atten * spotAtten;
        }
    #endif
}
#endif