@animech-public/playcanvas/build/playcanvas.dbg/src/scene/shader-lib/chunks/lit/frag/TBNderivative.js

PlayCanvas WebGL game engine

var TBNderivativePS = /* glsl */`
uniform float tbnBasis;

// http://www.thetenthplanet.de/archives/1180
void getTBN(vec3 tangent, vec3 binormal, vec3 normal) {
    vec2 uv = $UV;

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

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

    // construct a scale-invariant frame
    float denom = max( dot(T,T), dot(B,B) );
    float invmax = (denom == 0.0) ? 0.0 : tbnBasis / sqrt( denom );
    dTBN = mat3(T * invmax, -B * invmax, normal );
}
`;

export { TBNderivativePS as default };