#ifndef UNIVERSAL_PARALLAX_MAPPING_INCLUDED
#define UNIVERSAL_PARALLAX_MAPPING_INCLUDED

// Return view direction in tangent space, make sure tangentWS.w is already multiplied by GetOddNegativeScale()
half3 GetViewDirectionTangentSpace(half4 tangentWS, half3 normalWS, half3 viewDirWS)
{
    // must use interpolated tangent, bitangent and normal before they are normalized in the pixel shader.
    half3 unnormalizedNormalWS = normalWS;
    const half renormFactor = 1.0 / length(unnormalizedNormalWS);

    // use bitangent on the fly like in hdrp
    // IMPORTANT! If we ever support Flip on double sided materials ensure bitangent and tangent are NOT flipped.
    half crossSign = (tangentWS.w > 0.0 ? 1.0 : -1.0); // we do not need to multiple GetOddNegativeScale() here, as it is done in vertex shader
    half3 bitang = crossSign * cross(normalWS.xyz, tangentWS.xyz);

    half3 WorldSpaceNormal = renormFactor * normalWS.xyz;       // we want a unit length Normal Vector node in shader graph

    // to preserve mikktspace compliance we use same scale renormFactor as was used on the normal.
    // This is explained in section 2.2 in "surface gradient based bump mapping framework"
    half3 WorldSpaceTangent = renormFactor * tangentWS.xyz;
    half3 WorldSpaceBiTangent = renormFactor * bitang;

    half3x3 tangentSpaceTransform = half3x3(WorldSpaceTangent, WorldSpaceBiTangent, WorldSpaceNormal);
    half3 viewDirTS = mul(tangentSpaceTransform, viewDirWS);

    return viewDirTS;
}

#ifndef BUILTIN_TARGET_API
half2 ParallaxOffset1Step(half height, half amplitude, half3 viewDirTS)
{
    height = height * amplitude - amplitude / 2.0;
    half3 v = normalize(viewDirTS);
    v.z += 0.42;
    return height * (v.xy / v.z);
}
#endif

float2 ParallaxMapping(TEXTURE2D_PARAM(heightMap, sampler_heightMap), half3 viewDirTS, half scale, float2 uv)
{
    half h = SAMPLE_TEXTURE2D(heightMap, sampler_heightMap, uv).g;
    float2 offset = ParallaxOffset1Step(h, scale, viewDirTS);
    return offset;
}

float2 ParallaxMappingChannel(TEXTURE2D_PARAM(heightMap, sampler_heightMap), half3 viewDirTS, half scale, float2 uv, int channel)
{
    half h = SAMPLE_TEXTURE2D(heightMap, sampler_heightMap, uv)[channel];
    float2 offset = ParallaxOffset1Step(h, scale, viewDirTS);
    return offset;
}
#endif // UNIVERSAL_PARALLAX_MAPPING_INCLUDED