#ifndef CC_SURFACES_FRAGMENT_MODIFY_BASECOLOR_AND_TRANSPARENCY
// depends on CC_SURFACES_FRAGMENT_MODIFY_BASECOLOR_AND_TRANSPARENCY
vec4 SurfacesFragmentModifyBaseColorAndTransparency()
{
    return FSInput_vertexColor;
}
#endif

#ifndef CC_SURFACES_FRAGMENT_ALPHA_CLIP_ONLY
// depends on CC_SURFACES_FRAGMENT_ALPHA_CLIP_ONLY
// for base shape without color usage, such as render-to-shadow
void SurfacesFragmentAlphaClipOnly()
{
}
#endif


#ifndef CC_SURFACES_FRAGMENT_MODIFY_WORLD_NORMAL
// depends on CC_SURFACES_FRAGMENT_MODIFY_WORLD_NORMAL
vec3 SurfacesFragmentModifyWorldNormal()
{
    return normalize(FSInput_worldNormal);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_WORLD_TANGENT_AND_BINORMAL
// depends on CC_SURFACES_FRAGMENT_MODIFY_WORLD_TANGENT_AND_BINORMAL
void SurfacesFragmentModifyWorldTangentAndBinormal(inout vec3 worldTangent, inout vec3 worldBinormal, vec3 worldNormal)
{
    vec3 tangent = normalize(FSInput_worldTangent);

#if CC_SURFACES_USE_TANGENT_SPACE
    vec3 binormal = normalize(CalculateBinormal(worldNormal.xyz, tangent, FSInput_mirrorNormal));
    tangent = normalize(cross(binormal, worldNormal));
#else
    vec3 binormal = vec3(0.0, 0.0, 0.0);
#endif

    worldTangent = tangent;
    worldBinormal = binormal;
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_IOR
// depends on CC_SURFACES_FRAGMENT_MODIFY_IOR
float SurfacesFragmentModifyIOR()
{
    return 1.0;
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_ANISOTROPY_PARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_ANISOTROPY_PARAMS
// isRotation=1.0: shape(0~1), rotation(0~2PI), 0.0, 0.0
// or
// isRotation=0.0: shape(0~1), anisoDir.xyz(-1~1)
vec4 SurfacesFragmentModifyAnisotropyParams(out float isRotation)
{
    isRotation = 1.0;
    return vec4(1.0, 0.0, 0.0, 0.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_EMISSIVE
// depends on CC_SURFACES_FRAGMENT_MODIFY_EMISSIVE
vec3 SurfacesFragmentModifyEmissive()
{
    return vec3(0.0, 0.0, 0.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_PBRPARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_PBRPARAMS
vec4 SurfacesFragmentModifyPBRParams()
{
    // ao, roughness, metallic, specularIntensity
    return vec4(1.0, 0.5, 0.0, 0.5);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_TRANSMIT_SCATTERING_PARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_TRANSMIT_SCATTERING_PARAMS
// scattering related parameters and colors, shared by transmit diffuse and specular
vec4 SurfacesFragmentModifyTransmitScatteringParams()
{
    // x: extinction coef for out/in-scattering, 0 means disable scattering, thin object needs larger value such as 100-1000
    // y: in-scattering coef (constant phase function)
    // z: transmit normal type, default is 1 means using back face normal, 0 means using view-dependent normal, for shapeless materials such as hair
    // w: transmit distance, depending on CC_SURFACES_LIGHTING_USE_SHADOWMAP_TRANSMIT macro value:
    //    macro is 0: affect direct / env transmit lighting, 0 means disable scattering, (water depth, leaf / hair thicknessMap, ear / nose thicknessMap)
    //    macro is 1: only affect env transmit when shadow dir not match back normal (actual mesh thickness for ear / nose, nephrite)
    return vec4(1.0, 1.0, 1.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_TRANSMIT_IN_SCATTERING_COLOR
// depends on CC_SURFACES_FRAGMENT_MODIFY_TRANSMIT_IN_SCATTERING_COLOR
vec3 SurfacesFragmentModifyTransmitInScatteringColor()
{
    // added light multiplier
    return vec3(0.0);
}
#endif
#ifndef CC_SURFACES_FRAGMENT_MODIFY_TRANSMIT_OUT_SCATTERING_COLOR
// depends on CC_SURFACES_FRAGMENT_MODIFY_TRANSMIT_OUT_SCATTERING_COLOR
vec3 SurfacesFragmentModifyTransmitOutScatteringColor()
{
    // transmit background multiplier
    return vec3(1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_TRANSMIT_DIFFUSE_PARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_TRANSMIT_DIFFUSE_PARAMS
vec4 SurfacesFragmentModifyTransmitDiffuseParams()
{
    // this param valid only when CC_SURFACES_LIGHTING_USE_SHADOWMAP_TRANSMIT is 1
    // material should use cull none for shadow caster pass, and enable shadow casting and receive shadow

    // x: object (material part) thickness (worldspace unit bounding box max length), apply shadows for backlit only when shadowmap distance > object thickness, 0 means always apply shadows(thin object), SURFACES_MAX_TRANSMIT_DEPTH_VALUE means do not apply shadows.
    //    notice: setting too small a value for thick objects, no transmit light will disappear.
    // y: transmit area mask, limit area to avoid shadowmap coverage precision artifacts, default 1.0 means enable full transmit, and gradient value makes transmit lighting look smoother
    // z: environment transmit scale, useless (env transmit is not accuracy, some material should give 0 to disable, or use area mask instead)
    // w: shadowmap transmit distance scale, useless (very large model is hard to control transmit lighting through extinction coef, should use small value to scale its distance)
    return vec4(1.0, 1.0, 1.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_TRT_PARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_TRT_PARAMS
vec4 SurfacesFragmentModifyTRTParams()
{
    //x: roughness offset
    //y: lighting rotation offset
    //w: intensity
    return vec4(0.2, 0.0, 0.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_TRT_COLOR
// depends on CC_SURFACES_FRAGMENT_MODIFY_TRT_COLOR
vec3 SurfacesFragmentModifyTRTColor()
{
    return vec3(1.0, 1.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_TT_PARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_TT_PARAMS
vec4 SurfacesFragmentModifyTTParams()
{
    //x: scatter coef
    //w: intensity
    return vec4(0.0, 0.0, 0.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_TT_COLOR
// depends on CC_SURFACES_FRAGMENT_MODIFY_TT_COLOR
vec3 SurfacesFragmentModifyTTColor(in vec3 baseColor)
{
    // baseColor for reference
    return vec3(1.0, 1.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_SSS_PARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_SSS_PARAMS
vec4 SurfacesFragmentModifySSSParams()
{
    // x: sssIntensity, moisture
    // y: sssCurvature, for preintegrated sss
    // z: sssColoration, for sss transmitted light color with dark area
    // w: unused
    return vec4(1.0, 0.1, 1.0, 0.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_DUAL_LOBE_SPECULAR_PARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_DUAL_LOBE_SPECULAR_PARAMS
vec4 SurfacesFragmentModifyDualLobeSpecularParams(float roughness)
{
    //x: secondary lobe roughness, according to argument (first lobe roughness)
    //w: intensity
    return vec4(0.2, 0.0, 0.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_CLEAR_COAT_PARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_CLEAR_COAT_PARAMS
vec4 SurfacesFragmentModifyClearCoatParams()
{
    //x: coat roughness
    //y: coat ior
    //z: coat opacity
    //w: coat intensity
    return vec4(0.2, 1.5, 1.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_CLEAR_COAT_COLOR
// depends on CC_SURFACES_FRAGMENT_MODIFY_CLEAR_COAT_COLOR
vec3 SurfacesFragmentModifyClearCoatColor()
{
    // for iridescense color variation
    return vec3(1.0, 1.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_CLEAR_COAT_WORLD_NORMAL
// depends on CC_SURFACES_FRAGMENT_MODIFY_CLEAR_COAT_WORLD_NORMAL
vec3 SurfacesFragmentModifyClearCoatWorldNormal()
{
    return normalize(FSInput_worldNormal);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_SHEEN_PARAMS
// depends on CC_SURFACES_FRAGMENT_MODIFY_SHEEN_PARAMS
vec4 SurfacesFragmentModifySheenParams()
{
    //x: sheen roughness
    //y: sheen opacity
    //z: unused
    //w: sheen intensity
    return vec4(0.7, 1.0, 1.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_SHEEN_COLOR
// depends on CC_SURFACES_FRAGMENT_MODIFY_SHEEN_COLOR
vec3 SurfacesFragmentModifySheenColor()
{
    return vec3(1.0, 1.0, 1.0);
}
#endif

#ifndef CC_SURFACES_FRAGMENT_MODIFY_SHARED_DATA
// depends on CC_SURFACES_FRAGMENT_MODIFY_SHARED_DATA
// some material datas use shared raw data, avoid sample / calculate same raw data multiply times, use this function for better performance
// this function invokes at last
// should use corresponding shading-model header: #include <surfaces/data-structures/XXX> before function define
void SurfacesFragmentModifySharedData(inout SurfacesMaterialData surfaceData)
{
}
#endif