qt-everywhere-src-5.15.1/qtquick3d/src/runtimerender/res/effectlib/tangentSpaceNormalTexture.glsllib

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#ifndef FILE_NORMAL_TEXTURE_GLSLLIB
#define FILE_NORMAL_TEXTURE_GLSLLIB

#ifdef QSSG_DEFINE_API

#include "luminance.glsllib"
#include "monoChannel.glsllib"
#include "textureCoordinateInfo.glsllib"
#define wrap_clamp 0
#define wrap_repeat 1
#define wrap_mirrored_repeat 2
#include "rotationTranslationScale.glsllib"
#include "transformCoordinate.glsllib"

#endif

//interpreting the color values of a bitmap as a vector in tangent space
vec3 tangentSpaceNormalTexture( in sampler2D tex, in float factor, in bool flipTangentU, in bool flipTangentV
                              , in texture_coordinate_info uvw, in vec2 cropU, in vec2 cropV, in int wrapU, in int wrapV )
{
  // if we mirror repeat a tangent space texture, tangent space needs to be flipped for every other tile
  bool flipU = flipTangentU;
  bool flipV = flipTangentV;
  if ( wrapU == wrap_mirrored_repeat )
  {
    if (    ( ( 0.0 < uvw.position.x ) && ( int( uvw.position.x ) % 2 == 1 ) )
        ||  ( ( uvw.position.x < 0.0 ) && ( int( uvw.position.x ) % 2 == 0 ) ) )
    {
      flipU = !flipU;
    }
    if (    ( ( 0.0 < uvw.position.y ) && ( int( uvw.position.y ) % 2 == 1 ) )
        ||  ( ( uvw.position.y < 0.0 ) && ( int( uvw.position.y ) % 2 == 0 ) ) )
    {
      flipV = !flipV;
    }
  }

  vec3 tangent = 2.0 * texture( tex, uvw.position.xy ).xyz - 1.0;

  vec3 tangentU = normalize( flipU ? -uvw.tangent_u : uvw.tangent_u );
  vec3 tangentV = normalize( flipV ? -uvw.tangent_v : uvw.tangent_v );
  vec3 normal = normalize( cross( tangentU, tangentV ) );

  return( mix( normal, normalize( tangent.x * tangentU - tangent.y * tangentV + tangent.z * normal ), factor ) );
}

#include "textureCoordinateInfo.glsllib"

//Simpler version built to run from UIC image data
//In our case, we have already generated the texture coordinate x,y position
//TODO - figure out if we need to manipulate tangent_u, tangent_v.
vec3 defaultMaterialFileNormalTexture( in sampler2D sampler, in float factor, vec2 texCoord, vec3 tangent, vec3 binormal )
{
  // factor should be in [0,1] range
  return tangentSpaceNormalTexture( sampler, clamp(factor, 0.0, 1.0), false, false
                                  , textureCoordinateInfo( vec3( texCoord.x, texCoord.y, 0.0 ), tangent, binormal )
                                  , vec2( 0.000000, 1.000000 ), vec2( 0.000000, 1.000000 )
                                  , wrap_repeat, wrap_repeat);
}

#endif