Custom post-processing

Introduction

Godot provides many post-processing effects out of the box, including Bloom, DOF, and SSAO. Sometimes you want to write your own custom effect. Here’s how you can do so. Viewport, then render the Viewport inside a ViewportTexture and show it on the screen. Screen Reading Shaders Tutorial first. Note As of the time of writing, Godot does not support rendering to multiple buffers at the same time. Your post-processing shader will not have access to normals or other render passes. You only have access to the rendered frame.

Single pass post-processing

Viewport to render your scene to, and a scene to render your Viewport on the screen. You can use a ViewportContainer to display your Viewport on the entire screen or inside another Control node. Note Viewport gives you control over how the scene render, including the framerate, and you can use the ViewportContainer to render 3D objects in a 2D scene. Node2D with a ViewportContainer and finally a Viewport. Your Scene tab should look like this: Viewport, you can have whatever you want. This will contain your main scene. For this tutorial, we will use a field of random boxes: ShaderMaterial to the ViewportContainer, and assign a new shader resource to it. You can access your rendered Viewport with the built-in TEXTURE uniform. Note ViewportContainer, but if you do so, you will need to create your own uniform in the shader and pass the Viewport texture in manually, like so:

// Inside the Shader.uniform sampler2D ViewportTexture;

And you can pass the texture into the shader from GDScript like so:

# In GDScript.func _ready():  $Sprite.material.set_shader_param("ViewportTexture", $Viewport.get_texture())

Sobel filter.

shader_type canvas_item;void fragment() {    vec3 col = -8.0 * texture(TEXTURE, UV).xyz;    col += texture(TEXTURE, UV + vec2(0.0, SCREEN_PIXEL_SIZE.y)).xyz;    col += texture(TEXTURE, UV + vec2(0.0, -SCREEN_PIXEL_SIZE.y)).xyz;    col += texture(TEXTURE, UV + vec2(SCREEN_PIXEL_SIZE.x, 0.0)).xyz;    col += texture(TEXTURE, UV + vec2(-SCREEN_PIXEL_SIZE.x, 0.0)).xyz;    col += texture(TEXTURE, UV + SCREEN_PIXEL_SIZE.xy).xyz;    col += texture(TEXTURE, UV - SCREEN_PIXEL_SIZE.xy).xyz;    col += texture(TEXTURE, UV + vec2(-SCREEN_PIXEL_SIZE.x, SCREEN_PIXEL_SIZE.y)).xyz;    col += texture(TEXTURE, UV + vec2(SCREEN_PIXEL_SIZE.x, -SCREEN_PIXEL_SIZE.y)).xyz;    COLOR.xyz = col;}

Note The Sobel filter reads pixels in a 9x9 grid around the current pixel and adds them together, using weight. What makes it interesting is that it assigns weights to each pixel; +1 for each of the eight around the center and -8 for the center pixel. The choice of weights is called a “kernel”. You can use different kernels to create edge detection filters, outlines, and all sorts of effects.

Multi-pass post-processing

Some post-processing effects like blur are resource intensive. If you break them down in multiple passes however, you can make them run a lot faster. In a multipass material, each pass takes the result from the previous pass as an input and processes it. Viewport nodes. In the example above, you rendered the content of one Viewport object into the root Viewport, through a ViewportContainer node. You can do the same thing for a multi-pass shader by rendering the content of one Viewport into another and then rendering the last Viewport into the root Viewport. Your scene hierarchy will look something like this: Viewport node first. So if the order of the passes matters for your shaders, make sure that you assign the shader you want to apply first to the lowest ViewportContainer in the tree. Note You can also render your Viewports separately without nesting them like this. You just need to use two Viewports and to render them one after the other. Apart from the node structure, the steps are the same as with the single-pass post-processing shader. ViewportContainers. The order in which you apply the shaders does not matter:

shader_type canvas_item;// Blurs the screen in the X-direction.void fragment() {    vec3 col = texture(TEXTURE, UV).xyz * 0.16;    col += texture(TEXTURE, UV + vec2(SCREEN_PIXEL_SIZE.x, 0.0)).xyz * 0.15;    col += texture(TEXTURE, UV + vec2(-SCREEN_PIXEL_SIZE.x, 0.0)).xyz * 0.15;    col += texture(TEXTURE, UV + vec2(2.0 * SCREEN_PIXEL_SIZE.x, 0.0)).xyz * 0.12;    col += texture(TEXTURE, UV + vec2(2.0 * -SCREEN_PIXEL_SIZE.x, 0.0)).xyz * 0.12;    col += texture(TEXTURE, UV + vec2(3.0 * SCREEN_PIXEL_SIZE.x, 0.0)).xyz * 0.09;    col += texture(TEXTURE, UV + vec2(3.0 * -SCREEN_PIXEL_SIZE.x, 0.0)).xyz * 0.09;    col += texture(TEXTURE, UV + vec2(4.0 * SCREEN_PIXEL_SIZE.x, 0.0)).xyz * 0.05;    col += texture(TEXTURE, UV + vec2(4.0 * -SCREEN_PIXEL_SIZE.x, 0.0)).xyz * 0.05;    COLOR.xyz = col;}

shader_type canvas_item;// Blurs the screen in the Y-direction.void fragment() {    vec3 col = texture(TEXTURE, UV).xyz * 0.16;    col += texture(TEXTURE, UV + vec2(0.0, SCREEN_PIXEL_SIZE.y)).xyz * 0.15;    col += texture(TEXTURE, UV + vec2(0.0, -SCREEN_PIXEL_SIZE.y)).xyz * 0.15;    col += texture(TEXTURE, UV + vec2(0.0, 2.0 * SCREEN_PIXEL_SIZE.y)).xyz * 0.12;    col += texture(TEXTURE, UV + vec2(0.0, 2.0 * -SCREEN_PIXEL_SIZE.y)).xyz * 0.12;    col += texture(TEXTURE, UV + vec2(0.0, 3.0 * SCREEN_PIXEL_SIZE.y)).xyz * 0.09;    col += texture(TEXTURE, UV + vec2(0.0, 3.0 * -SCREEN_PIXEL_SIZE.y)).xyz * 0.09;    col += texture(TEXTURE, UV + vec2(0.0, 4.0 * SCREEN_PIXEL_SIZE.y)).xyz * 0.05;    col += texture(TEXTURE, UV + vec2(0.0, 4.0 * -SCREEN_PIXEL_SIZE.y)).xyz * 0.05;    COLOR.xyz = col;}

Using the above code, you should end up with a full screen blur effect like below. Viewport nodes work, see the Viewports Tutorial.