three.js shader snippets.glsl

// world position
vPositionW = vec3( vec4( position, 1.0 ) * modelMatrix);

// world normal
vNormalW = normalize( vec3( vec4( normal, 0.0 ) * modelMatrix ) );

// world camera direction 
vec3 viewDirectionW = normalize(cameraPosition - vPositionW);

// fresnel, calc with dot mult between view and normal
float fresnel = dot(viewDirectionW, vNormalW);
// then clamp
fresnelTerm = clamp(1.0 - fresnelTerm, 0., 1.);