#if defined(BUMP) || defined(CLEARCOAT_BUMP) || defined(ANISOTROPIC)
	#if defined(TANGENT) && defined(NORMAL) 
		varying mat3 vTBN;
	#endif

	#ifdef OBJECTSPACE_NORMALMAP
		uniform mat4 normalMatrix;
	#endif

	vec3 perturbNormal(mat3 cotangentFrame, vec3 textureSample, float scale)
	{
		textureSample = textureSample * 2.0 - 1.0;

		#ifdef NORMALXYSCALE
			textureSample = normalize(textureSample * vec3(scale, scale, 1.0));
		#endif

		return normalize(cotangentFrame * textureSample);
	}

	// Thanks to http://www.thetenthplanet.de/archives/1180
	mat3 cotangent_frame(vec3 normal, vec3 p, vec2 uv, vec2 tangentSpaceParams)
	{
		// flip the uv for the backface
		uv = gl_FrontFacing ? uv : -uv;

		// get edge vectors of the pixel triangle
		vec3 dp1 = dFdx(p);
		vec3 dp2 = dFdy(p);
		vec2 duv1 = dFdx(uv);
		vec2 duv2 = dFdy(uv);

		// solve the linear system
		vec3 dp2perp = cross(dp2, normal);
		vec3 dp1perp = cross(normal, dp1);
		vec3 tangent = dp2perp * duv1.x + dp1perp * duv2.x;
		vec3 bitangent = dp2perp * duv1.y + dp1perp * duv2.y;

		// invert the tangent/bitangent if requested
		tangent *= tangentSpaceParams.x;
		bitangent *= tangentSpaceParams.y;

		// construct a scale-invariant frame
		float invmax = inversesqrt(max(dot(tangent, tangent), dot(bitangent, bitangent)));
		return mat3(tangent * invmax, bitangent * invmax, normal);
	}
#endif

#if defined(BUMP)
	#if BUMPDIRECTUV == 1
		#define vBumpUV vMainUV1
	#elif BUMPDIRECTUV == 2
		#define vBumpUV vMainUV2
	#else
		varying vec2 vBumpUV;
	#endif
	uniform sampler2D bumpSampler;
	
	vec3 perturbNormal(mat3 cotangentFrame, vec2 uv)
	{
		return perturbNormal(cotangentFrame, texture2D(bumpSampler, uv).xyz, vBumpInfos.y);
	}
#endif

#if defined(BUMP)
	vec3 perturbNormal(mat3 cotangentFrame, vec3 color)
	{
		return perturbNormal(cotangentFrame, color, vBumpInfos.y);
	}

	// Thanks to http://www.thetenthplanet.de/archives/1180
	mat3 cotangent_frame(vec3 normal, vec3 p, vec2 uv)
	{
		return cotangent_frame(normal, p, uv, vTangentSpaceParams);
	}
#endif

#if defined(BUMP) && defined(PARALLAX)
	const float minSamples = 4.;
	const float maxSamples = 15.;
	const int iMaxSamples = 15;

	// http://www.gamedev.net/page/resources/_/technical/graphics-programming-and-theory/a-closer-look-at-parallax-occlusion-mapping-r3262
	vec2 parallaxOcclusion(vec3 vViewDirCoT, vec3 vNormalCoT, vec2 texCoord, float parallaxScale) {

		float parallaxLimit = length(vViewDirCoT.xy) / vViewDirCoT.z;
		parallaxLimit *= parallaxScale;
		vec2 vOffsetDir = normalize(vViewDirCoT.xy);
		vec2 vMaxOffset = vOffsetDir * parallaxLimit;
		float numSamples = maxSamples + (dot(vViewDirCoT, vNormalCoT) * (minSamples - maxSamples));
		float stepSize = 1.0 / numSamples;

		// Initialize the starting view ray height and the texture offsets.
		float currRayHeight = 1.0;
		vec2 vCurrOffset = vec2(0, 0);
		vec2 vLastOffset = vec2(0, 0);

		float lastSampledHeight = 1.0;
		float currSampledHeight = 1.0;

		for (int i = 0; i < iMaxSamples; i++)
		{
			currSampledHeight = texture2D(bumpSampler, vBumpUV + vCurrOffset).w;

			// Test if the view ray has intersected the surface.
			if (currSampledHeight > currRayHeight)
			{
				float delta1 = currSampledHeight - currRayHeight;
				float delta2 = (currRayHeight + stepSize) - lastSampledHeight;
				float ratio = delta1 / (delta1 + delta2);
				vCurrOffset = (ratio)* vLastOffset + (1.0 - ratio) * vCurrOffset;

				// Force the exit of the loop
				break;
			}
			else
			{
				currRayHeight -= stepSize;
				vLastOffset = vCurrOffset;
				vCurrOffset += stepSize * vMaxOffset;

				lastSampledHeight = currSampledHeight;
			}
		}

		return vCurrOffset;
	}

	vec2 parallaxOffset(vec3 viewDir, float heightScale)
	{
		// calculate amount of offset for Parallax Mapping With Offset Limiting
		float height = texture2D(bumpSampler, vBumpUV).w;
		vec2 texCoordOffset = heightScale * viewDir.xy * height;
		return -texCoordOffset;
	}
#endif