GLSL - add effect to all screen instead to a specific texture

Newbie & Debugging Questions
#1

Hello programmers,
I wish to add a vignette effect to the screen.

My fragment shader -


varying vec4 vColor;
varying vec2 vTexCoord;

uniform vec2 screenSize;

uniform sampler2D u_texture;
uniform vec4 gameTime;

const float RADIUS = 0.75;

const float SOFTNESS = 0.6;

void main() {

	vec4 texColor = texture2D(u_texture, vTexCoord);

    vec4 timedColor = (vColor + gameTime);

	vec2 position = (gl_FragCoord.xy / screenSize.xy) - vec2(0.5);
	float len = length(position);

	float vignette = smoothstep(RADIUS, RADIUS-SOFTNESS, len);

	texColor.rgb = mix(texColor.rgb, texColor.rgb * vignette, 0.5);
		
	gl_FragColor = vec4(texColor.rgb * timedColor.rgb, texColor.a);
}

the code above, adds the vignette effect only to a texture.
but i want it to add the vignette effect to the whole screen.
I thought may be i should add a transparent background image with the vignette effect on top of everything.

What do you think? what is the best way to implement this in GLSL?
Thanks bros :slight_smile: