VHS and CRT monitor effect

An effect to simulate a CRT monitor or an old TV. It also has settings to make it look like an old VHS recording (discolorations, noise, and rolling distortion, see image below).

This is a “true” CRT simulation with every scanline being divided into multiple sets of red, green, and blue squares – the technique called aperture grille.

It has many, many uniforms. I won’t list them all here but they include settings for scanlines, grille, pixels, discolorations, screen warping, noise, distortions, etc.

Important instructions
You can use the shader in two ways:

  1. To affect the node it is applied to, like a Sprite or ViewportContainer. Uncheck the Overlay parameter in the inspector.
  2. As an overlay filter to affect the nodes below it in the Scene hierarchy. Add the shader to a ColorRect and check the Overlay parameter in the inspector.

On Mac there is potentially a bug causing the Overlay check to not work properly. In that case, if you want to use the shader as an overlay, change overlay ? SCREEN_TEXTURE : TEXTURE to only SCREEN_TEXTURE on lines 129-140, and vec2 uv = overlay ? warp(SCREEN_UV) : warp(UV); to vec2 uv = warp(SCREEN_UV); on line 98.

Shader code
/*
Shader from Godot Shaders - the free shader library.
godotshaders.com/shader/VHS-and-CRT-monitor-effect

This shader is under CC0 license. Feel free to use, improve and 
change this shader according to your needs and consider sharing 
the modified result to godotshaders.com.
*/

shader_type canvas_item;

//*** IMPORTANT! ***/ 
// - If you are using this shader to affect the node it is applied to set 'overlay' to false (unchecked in the instepctor).
// - If you are using this shader as an overlay, and want the shader to affect the nodes below in the Scene hierarchy,
//   set 'overlay' to true (checked in the inspector).
// On Mac there is potentially a bug causing this to not work properly. If that is the case and you want to use the shader as an overlay
// change all "overlay ? SCREEN_TEXTURE : TEXTURE" to only "SCREEN_TEXTURE" on lines 129-140, and "vec2 uv = overlay ? warp(SCREEN_UV) : warp(UV);"
// to "vec2 uv = warp(SCREEN_UV);" on line 98.
uniform bool overlay = false;

uniform float scanlines_opacity : hint_range(0.0, 1.0) = 0.4;
uniform float scanlines_width : hint_range(0.0, 0.5) = 0.25;
uniform float grille_opacity : hint_range(0.0, 1.0) = 0.3;
uniform vec2 resolution = vec2(640.0, 480.0); // Set the number of rows and columns the texture will be divided in. Scanlines and grille will make a square based on these values

uniform bool pixelate = true; // Fill each square ("pixel") with a sampled color, creating a pixel look and a more accurate representation of how a CRT monitor would work.

uniform bool roll = true;
uniform float roll_speed = 8.0; // Positive values are down, negative are up
uniform float roll_size : hint_range(0.0, 100.0) = 15.0;
uniform float roll_variation : hint_range(0.1, 5.0) = 1.8; // This valie is not an exact science. You have to play around with the value to find a look you like. How this works is explained in the code below.
uniform float distort_intensity : hint_range(0.0, 0.2) = 0.05; // The distortion created by the rolling effect.

uniform float noise_opacity : hint_range(0.0, 1.0) = 0.4;
uniform float noise_speed = 5.0; // There is a movement in the noise pattern that can be hard to see first. This sets the speed of that movement.

uniform float static_noise_intensity : hint_range(0.0, 1.0) = 0.06;

uniform float aberration : hint_range(-1.0, 1.0) = 0.03; // Chromatic aberration, a distortion on each color channel.
uniform float brightness = 1.4; // When adding scanline gaps and grille the image can get very dark. Brightness tries to compensate for that.
uniform bool discolor = true; // Add a discolor effect simulating a VHS

uniform float warp_amount :hint_range(0.0, 5.0) = 1.0; // Warp the texture edges simulating the curved glass of a CRT monitor or old TV.
uniform bool clip_warp = false;

uniform float vignette_intensity = 0.4; // Size of the vignette, how far towards the middle it should go.
uniform float vignette_opacity : hint_range(0.0, 1.0) = 0.5;

// Used by the noise functin to generate a pseudo random value between 0.0 and 1.0
vec2 random(vec2 uv){
    uv = vec2( dot(uv, vec2(127.1,311.7) ),
               dot(uv, vec2(269.5,183.3) ) );
    return -1.0 + 2.0 * fract(sin(uv) * 43758.5453123);
}

// Generate a Perlin noise used by the distortion effects
float noise(vec2 uv) {
    vec2 uv_index = floor(uv);
    vec2 uv_fract = fract(uv);

    vec2 blur = smoothstep(0.0, 1.0, uv_fract);

    return mix( mix( dot( random(uv_index + vec2(0.0,0.0) ), uv_fract - vec2(0.0,0.0) ),
                     dot( random(uv_index + vec2(1.0,0.0) ), uv_fract - vec2(1.0,0.0) ), blur.x),
                mix( dot( random(uv_index + vec2(0.0,1.0) ), uv_fract - vec2(0.0,1.0) ),
                     dot( random(uv_index + vec2(1.0,1.0) ), uv_fract - vec2(1.0,1.0) ), blur.x), blur.y) * 0.5 + 0.5;
}

// Takes in the UV and warps the edges, creating the spherized effect
vec2 warp(vec2 uv){
	vec2 delta = uv - 0.5;
	float delta2 = dot(delta.xy, delta.xy);
	float delta4 = delta2 * delta2;
	float delta_offset = delta4 * warp_amount;
	
	return uv + delta * delta_offset;
}

// Adds a black border to hide stretched pixel created by the warp effect
float border (vec2 uv){
	float radius = min(warp_amount, 0.08);
	radius = max(min(min(abs(radius * 2.0), abs(1.0)), abs(1.0)), 1e-5);
	vec2 abs_uv = abs(uv * 2.0 - 1.0) - vec2(1.0, 1.0) + radius;
	float dist = length(max(vec2(0.0), abs_uv)) / radius;
	float square = smoothstep(0.96, 1.0, dist);
	return clamp(1.0 - square, 0.0, 1.0);
}

// Adds a vignette shadow to the edges of the image
float vignette(vec2 uv){
	uv *= 1.0 - uv.xy;
	float vignette = uv.x * uv.y * 15.0;
	return pow(vignette, vignette_intensity * vignette_opacity);
}

void fragment()
{
	vec2 uv = overlay ? warp(SCREEN_UV) : warp(UV); // Warp the uv. uv will be used in most cases instead of UV to keep the warping
	vec2 text_uv = uv;
	vec2 roll_uv = vec2(0.0);
	float time = roll ? TIME : 0.0;
	

	// Pixelate the texture based on the given resolution.
	if (pixelate)
	{
		text_uv = ceil(uv * resolution) / resolution;
	}
	
	// Create the rolling effect. We need roll_line a bit later to make the noise effect.
	// That is why this runs if roll is true OR noise_opacity is over 0.
	float roll_line = 0.0;
	if (roll || noise_opacity > 0.0)
	{
		// Create the areas/lines where the texture will be distorted.
		roll_line = smoothstep(0.3, 0.9, sin(uv.y * roll_size - (time * roll_speed) ) );
		// Create more lines of a different size and apply to the first set of lines. This creates a bit of variation.
		roll_line *= roll_line * smoothstep(0.3, 0.9, sin(uv.y * roll_size * roll_variation - (time * roll_speed * roll_variation) ) );
		// Distort the UV where where the lines are
		roll_uv = vec2(( roll_line * distort_intensity * (1.-UV.x)), 0.0);
	}
	
	vec4 text;
	if (roll)
	{
		// If roll is true distort the texture with roll_uv. The texture is split up into RGB to 
		// make some chromatic aberration. We apply the aberration to the red and green channels accorging to the aberration parameter
		// and intensify it a bit in the roll distortion.
		text.r = texture(SCREEN_TEXTURE, text_uv + roll_uv * 0.8 + vec2(aberration, 0.0) * .1).r;
		text.g = texture(SCREEN_TEXTURE, text_uv + roll_uv * 1.2 - vec2(aberration, 0.0) * .1 ).g;
		text.b = texture(SCREEN_TEXTURE, text_uv + roll_uv).b;
		text.a = 1.0;
	}
	else
	{
		// If roll is false only apply the aberration without any distorion. The aberration values are very small so the .1 is only 
		// to make the slider in the Inspector less sensitive.
		text.r = texture(SCREEN_TEXTURE, text_uv + vec2(aberration, 0.0) * .1).r;
		text.g = texture(SCREEN_TEXTURE, text_uv - vec2(aberration, 0.0) * .1).g;
		text.b = texture(SCREEN_TEXTURE, text_uv).b;
		text.a = 1.0;
	}
	
	float r = text.r;
	float g = text.g;
	float b = text.b;
	
	uv = warp(UV);
	
	// CRT monitors don't have pixels but groups of red, green and blue dots or lines, called grille. We isolate the texture's color channels 
	// and divide it up in 3 offsetted lines to show the red, green and blue colors next to each other, with a small black gap between.
	if (grille_opacity > 0.0){
		
		float g_r = smoothstep(0.85, 0.95, abs(sin(uv.x * (resolution.x * 3.14159265))));
		r = mix(r, r * g_r, grille_opacity);
		
		float g_g = smoothstep(0.85, 0.95, abs(sin(1.05 + uv.x * (resolution.x * 3.14159265))));
		g = mix(g, g * g_g, grille_opacity);
		
		float b_b = smoothstep(0.85, 0.95, abs(sin(2.1 + uv.x * (resolution.x * 3.14159265))));
		b = mix(b, b * b_b, grille_opacity);
		
	}
	
	// Apply the grille to the texture's color channels and apply Brightness. Since the grille and the scanlines (below) make the image very dark you
	// can compensate by increasing the brightness.
	text.r = clamp(r * brightness, 0.0, 1.0);
	text.g = clamp(g * brightness, 0.0, 1.0);
	text.b = clamp(b * brightness, 0.0, 1.0);
	
	// Scanlines are the horizontal lines that make up the image on a CRT monitor. 
	// Here we are actual setting the black gap between each line, which I guess is not the right definition of the word, but you get the idea  
	float scanlines = 0.5;
	if (scanlines_opacity > 0.0)
	{
		// Same technique as above, create lines with sine and applying it to the texture. Smoothstep to allow setting the line size.
		scanlines = smoothstep(scanlines_width, scanlines_width + 0.5, abs(sin(uv.y * (resolution.y * 3.14159265))));
		text.rgb = mix(text.rgb, text.rgb * vec3(scanlines), scanlines_opacity);
	}
	
	// Apply the banded noise.
	if (noise_opacity > 0.0)
	{
		// Generate a noise pattern that is very stretched horizontally, and animate it with noise_speed
		float noise = smoothstep(0.4, 0.5, noise(uv * vec2(2.0, 200.0) + vec2(10.0, (TIME * (noise_speed))) ) );
		
		// We use roll_line (set above) to define how big the noise should be vertically (multiplying cuts off all black parts).
		// We also add in some basic noise with random() to break up the noise pattern above. The noise is sized according to 
		// the resolution value set in the inspector. If you don't like this look you can 
		// change "ceil(uv * resolution) / resolution" to only "uv" to make it less pixelated. Or multiply resolution with som value
		// greater than 1.0 to make them smaller.
		roll_line *= noise * scanlines * clamp(random((ceil(uv * resolution) / resolution) + vec2(TIME * 0.8, 0.0)).x + 0.8, 0.0, 1.0);
		// Add it to the texture based on noise_opacity
		text.rgb = clamp(mix(text.rgb, text.rgb + roll_line, noise_opacity), vec3(0.0), vec3(1.0));
	}
	
	// Apply static noise by generating it over the whole screen in the same way as above
	if (static_noise_intensity > 0.0)
	{
		text.rgb += clamp(random((ceil(uv * resolution) / resolution) + fract(TIME)).x, 0.0, 1.0) * static_noise_intensity;
	}
	
	// Apply a black border to hide imperfections caused by the warping.
	// Also apply the vignette
	text.rgb *= border(uv);
	text.rgb *= vignette(uv);
	// Hides the black border and make that area transparent. Good if you want to add the the texture on top an image of a TV or monitor.
	if (clip_warp)
	{
		text.a = border(uv);
	}
	
	// Apply discoloration to get a VHS look (lower saturation and higher contrast)
	// You can play with the values below or expose them in the Inspector.
	float saturation = 0.5;
	float contrast = 1.2;
	if (discolor)
	{
		// Saturation
		vec3 greyscale = vec3(text.r + text.g + text.b) / 3.;
		text.rgb = mix(text.rgb, greyscale, saturation);
		
		// Contrast
		float midpoint = pow(0.5, 2.2);
		text.rgb = (text.rgb - vec3(midpoint)) * contrast + midpoint;
	}
	
	COLOR = text;
}
Tags
monitor, retro, tv, video, video games
The shader code and all code snippets in this post are under CC0 license and can be used freely without the author's permission. Images and videos, and assets depicted in those, do not fall under this license. For more info, see our License terms.

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Zorochase
Zorochase
4 months ago

Cool shader, but I can’t seem to get it to work. I applied it to a ViewportContainer with a Viewport as a child and a simple Spatial scene for testing as a child of that. The ViewportContainer also has a ShaderMaterial with this shader attached. This is all I see, both in editor and when I run the game. I must be doing something wrong, but I’m not sure what as I’ve used this setup for other effects like this and it’s worked fine.

Rakun
Rakun
4 months ago
Reply to  Zorochase

Same effect for me.

Zorochase
Zorochase
4 months ago
Reply to  pend00

Well, that’s not the issue for me as I was using GLES3 to test it. I made a fresh scene with that exact same node setup and its just not working. I have tried saving the ShaderMaterial with the shader attached and in its own file too, but that didn’t fix the problem. Here’s what my editor looks like: https://imgur.com/JFdjKkV

Rabid
Rabid
4 months ago
Reply to  pend00

I tried doing so, but no result. I’ve created a new project from scratch in case I’m messing up something. https://imgur.com/a/JU3fvN7

Edit: Btw thanks for taking the time to help us getting this sorted out, your shader looks amazing in the pictures πŸ™‚

Last edited 4 months ago by Rabid
Zorochase
Zorochase
4 months ago
Reply to  pend00
Rabid
Rabid
4 months ago
Reply to  pend00

Still no luck I’m afraid. https://imgur.com/a/COwSBRE

Did you try to put the shader on an empty new project with the same hierarchy we did? Maybe there’s something in the settings that you changed while working on the project and that’s why we are getting the white screen. Or maybe we are putting the shader on the wrong place or with the wrong material? I’m a total noob on shaders so maybe I’m totally wrong…

Zorochase
Zorochase
4 months ago
Reply to  pend00

This may/may not help narrow it down, but this is definitely something wrong with Godot. I converted the shader to a ShaderToy shader, and it works fine on there with both images and video, as you can see here. If you want to try it for yourself, you can copy it from this pastebin link, go to the site, make a new shader, paste it in and choose any image/video input.

Zorochase
Zorochase
4 months ago
Reply to  pend00

I just found the problematic lines: on lines 161 through 163, you clamp text.r, text.g, and text.b incorrectly by passing the range values first, like so:

text.r = clamp(0.0, 1.0, r * brightness);
text.g = clamp(0.0, 1.0, g * brightness);
text.b = clamp(0.0, 1.0, b * brightness);

I changed these to:

text.r = clamp(r * brightness, 0.0, 1.0);
text.g = clamp(g * brightness, 0.0, 1.0);
text.b = clamp(b * brightness, 0.0, 1.0);

You made the same mistake when calling clamp again later, on line 188, you wrote:

text.rgb = clamp(vec3(0.0), vec3(1.0), mix(text.rgb, text.rgb + roll_line, noise_opacity));

Changing this to:

text.rgb = clamp(mix(text.rgb, text.rgb + roll_line, noise_opacity), vec3(0.0), vec3(1.0));

fixed the shader. I now see the image, as expected:comment image

Last edited 4 months ago by Zorochase
Rakun
Rakun
4 months ago
Reply to  Zorochase

Used this shader in 2D with icon, and icon is now upside down.

Zorochase
Zorochase
4 months ago
Reply to  Rakun

If you’re using a Viewport node to display everything, click on the Viewport, and in the inspector, in the “Render Target” dropdown, check “V Flip”.

Rabid
Rabid
4 months ago
Reply to  Zorochase

Thanks Zorochase!! That worked. Thanks also pend00 for your shader and your time πŸ˜€

Rabid
Rabid
4 months ago
Reply to  pend00

Where did you put the shader? I’m having the same issue as Zorochase, with all i see is blank when I add the shader. https://imgur.com/a/KBeGxPz

beebster
beebster
4 months ago

Worked a treat. Added shader to ColorRect node as overlay and everything underneath treated to CRT goodness πŸ™‚

SRC Corp
SRC Corp
3 months ago

Thanks alot for providing this awesome shader!
Now I can use it for my fantasy console, ConSoal!