three.js/src/renderers/shaders/ShaderLib/meshmatcap_frag.glsl.js

export default /* glsl */`
#define MATCAP

uniform vec3 diffuse;
uniform float opacity;
uniform sampler2D matcap;

varying vec3 vViewPosition;

#ifndef FLAT_SHADED

	varying vec3 vNormal;

	#ifdef USE_TANGENT

		varying vec3 vTangent;
		varying vec3 vBitangent;

	#endif

#endif

#include <common>
#include <dithering_pars_fragment>
#include <color_pars_fragment>
#include <uv_pars_fragment>
#include <map_pars_fragment>
#include <alphamap_pars_fragment>

#include <fog_pars_fragment>
#include <bumpmap_pars_fragment>
#include <normalmap_pars_fragment>
#include <logdepthbuf_pars_fragment>
#include <clipping_planes_pars_fragment>

void main() {

	#include <clipping_planes_fragment>

	vec4 diffuseColor = vec4( diffuse, opacity );

	#include <logdepthbuf_fragment>
	#include <map_fragment>
	#include <color_fragment>
	#include <alphamap_fragment>
	#include <alphatest_fragment>
	#include <normal_fragment_begin>
	#include <normal_fragment_maps>

	vec3 viewDir = normalize( vViewPosition );
	vec3 x = normalize( vec3( viewDir.z, 0.0, - viewDir.x ) );
	vec3 y = cross( viewDir, x );
	vec2 uv = vec2( dot( x, normal ), dot( y, normal ) ) * 0.495 + 0.5; // 0.495 to remove artifacts caused by undersized matcap disks

	#ifdef USE_MATCAP

		vec4 matcapColor = texture2D( matcap, uv );
		matcapColor = matcapTexelToLinear( matcapColor );

	#else

		vec4 matcapColor = vec4( 1.0 );

	#endif

	vec3 outgoingLight = diffuseColor.rgb * matcapColor.rgb;

	gl_FragColor = vec4( outgoingLight, diffuseColor.a );

	#include <tonemapping_fragment>
	#include <encodings_fragment>
	#include <fog_fragment>
	#include <premultiplied_alpha_fragment>
	#include <dithering_fragment>

}
`;