Toon shading add antialiasing (#24406)

* Toon shading add antialiasing

* Update gradientmap_pars_fragment.glsl.js

* Update gradientmap_pars_fragment.glsl.js

* Update gradientmap_pars_fragment.glsl.js

Co-authored-by: Michael Herzog <[email protected]>

src/renderers/shaders/ShaderChunk/gradientmap_pars_fragment.glsl.js

@@ -18,7 +18,8 @@ vec3 getGradientIrradiance( vec3 normal, vec3 lightDirection ) {
 
 	#else
 
-		return ( coord.x < 0.7 ) ? vec3( 0.7 ) : vec3( 1.0 );
+		vec2 fw = fwidth( coord ) * 0.5;
+		return mix( vec3( 0.7 ), vec3( 1.0 ), smoothstep( 0.7 - fw.x, 0.7 + fw.x, coord.x ) );
 
 	#endif