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

export const vertex = /* glsl */`
varying vec2 vUv;
uniform mat3 uvTransform;

void main() {

	vUv = ( uvTransform * vec3( uv, 1 ) ).xy;

	gl_Position = vec4( position.xy, 1.0, 1.0 );

}
`;

export const fragment = /* glsl */`
uniform sampler2D t2D;
uniform float backgroundIntensity;

varying vec2 vUv;

void main() {

	vec4 texColor = texture2D( t2D, vUv );

	#ifdef DECODE_VIDEO_TEXTURE

		// use inline sRGB decode until browsers properly support SRGB8_APLHA8 with video textures

		texColor = vec4( mix( pow( texColor.rgb * 0.9478672986 + vec3( 0.0521327014 ), vec3( 2.4 ) ), texColor.rgb * 0.0773993808, vec3( lessThanEqual( texColor.rgb, vec3( 0.04045 ) ) ) ), texColor.w );

	#endif

	texColor.rgb *= backgroundIntensity;

	gl_FragColor = texColor;

	#include <tonemapping_fragment>
	#include <colorspace_fragment>

}
`;