shader-basics

name	shader-basics
description	Use when implementing shaders — Godot shader language, visual shaders, common visual recipes, and post-processing effects

Shaders in Godot 4.3+

All examples target Godot 4.3+ with no deprecated APIs.

Related skills: animation-system for shader-driven effects like hit flash, godot-optimization for shader performance considerations, camera-system for post-processing camera effects, 2d-essentials for 2D lighting, pixel-art shaders, and CanvasTexture normal maps, 3d-essentials for spatial shaders and environment materials, particles-vfx for custom particle shaders, tween-animation for animating shader parameters at runtime.

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1. Core Concepts

Shader Types

Shader Type	Applied To	Use For
canvas_item	2D nodes (Sprite2D, Control, etc.)	2D effects — outlines, dissolve, color swap
spatial	3D meshes (MeshInstance3D)	3D materials — water, terrain, toon shading
particles	GPUParticles2D/3D	Custom particle behavior
sky	WorldEnvironment	Procedural sky rendering
fog	FogVolume	Volumetric fog effects

Shader vs ShaderMaterial

Shader (.gdshader)        → The code (GLSL-like language)
ShaderMaterial            → Instance of a shader with specific uniform values
CanvasItemMaterial / StandardMaterial3D → Built-in materials (no code needed)

Multiple nodes can share the same Shader but have different ShaderMaterial instances with different uniform values (e.g., same dissolve shader but different dissolve progress per enemy).

Creating a Shader

1. Select a node (e.g., Sprite2D)
2. In Inspector → Material → New ShaderMaterial
3. On the ShaderMaterial → Shader → New Shader
4. Edit the .gdshader file in the built-in editor

Or create a .gdshader file directly in the FileSystem dock.

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2. Godot Shader Language Basics

Godot uses a GLSL ES 3.0-like language with Godot-specific additions.

Minimal Canvas Item Shader

shader_type canvas_item;

void fragment() {
    // COLOR is the output pixel color
    // TEXTURE is the sprite's texture
    // UV is the texture coordinate (0,0 top-left to 1,1 bottom-right)
    vec4 tex = texture(TEXTURE, UV);
    COLOR = tex;
}

Minimal Spatial Shader

shader_type spatial;

void fragment() {
    // ALBEDO is the base color (vec3)
    ALBEDO = vec3(0.8, 0.2, 0.2);
}

Built-in Variables (canvas_item)

Variable	Type	Description
UV	vec2	Texture coordinates
COLOR	vec4	Output color (set this in fragment())
TEXTURE	sampler2D	The node's texture
VERTEX	vec2	Vertex position (in vertex())
TIME	float	Elapsed time in seconds
SCREEN_UV	vec2	Screen-space UV (for screen effects)

SCREEN_TEXTURE was removed in Godot 4.0. To read the screen, declare a uniform: uniform sampler2D screen_texture : hint_screen_texture, filter_linear_mipmap;

Built-in Variables (spatial)

Variable	Type	Description
ALBEDO	vec3	Base surface color
METALLIC	float	Metallic value (0.0–1.0)
ROUGHNESS	float	Roughness value (0.0–1.0)
NORMAL	vec3	Surface normal (for normal mapping)
EMISSION	vec3	Emissive color
ALPHA	float	Transparency (enable in render mode)
VERTEX	vec3	Vertex position (in vertex())

Uniforms (Shader Parameters)

Uniforms expose shader values to the Inspector and code.

shader_type canvas_item;

uniform float speed : hint_range(0.0, 10.0, 0.1) = 1.0;
uniform vec4 tint_color : source_color = vec4(1.0, 1.0, 1.0, 1.0);
uniform sampler2D noise_texture : filter_linear_mipmap;

void fragment() {
    vec4 tex = texture(TEXTURE, UV);
    COLOR = tex * tint_color;
}

Common Uniform Hints

Hint	Type	Description
hint_range(min, max, step)	float/int	Slider in Inspector
source_color	vec4	Color picker in Inspector
filter_linear_mipmap	sampler2D	Texture filtering mode
repeat_enable	sampler2D	Allow texture tiling
hint_normal	sampler2D	Treat as normal map

Setting Uniforms from Code

GDScript

var mat: ShaderMaterial = $Sprite2D.material
mat.set_shader_parameter("speed", 2.0)
mat.set_shader_parameter("tint_color", Color.RED)

C#

var mat = GetNode<Sprite2D>("Sprite2D").Material as ShaderMaterial;
mat.SetShaderParameter("speed", 2.0f);
mat.SetShaderParameter("tint_color", Colors.Red);

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3. Common 2D Shader Recipes

The canvas_item recipes most projects need: dissolve (noise + edge glow), outline (sample neighbors, expand alpha), flash-white (uniform-driven hit effect), color swap (palette shift), scrolling UV (water/lava/clouds), wave distortion.

See references/2d-shader-recipes.md for complete shader code for all six recipes.

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4. Common 3D Shader Recipes

Spatial-shader recipes: toon/cel shading (banded NdotL), rim lighting / Fresnel (1 - NdotV), simple water surface (UV scroll + normal-map blend + Fresnel).

See references/3d-shader-recipes.md for the full shader source for each recipe.

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5. Visual Shaders

Visual shaders provide a node-based graph editor — no code required.

When to Use Visual Shaders

Use Visual Shaders When	Use Code Shaders When
Prototyping effects quickly	Complex math or branching logic
Artists need to tweak values	Need precise control over every line
Learning shader concepts	Performance-critical shaders
Simple effects (color adjust, UV scroll)	Loops or advanced techniques

Creating a Visual Shader

1. Select node → Inspector → Material → New ShaderMaterial
2. Shader → New VisualShader
3. Click the shader to open the Visual Shader editor
4. Add nodes from the palette, connect pins
5. Output nodes (Output, FragmentOutput) are pre-placed

Key Visual Shader Nodes

Node	Purpose
Texture2D	Sample a texture
ColorConstant	Solid color value
VectorOp	Math operations on vectors
ScalarOp	Math operations on floats
Mix	Lerp between two values
Step / SmoothStep	Threshold / smooth threshold
Time	Current time (for animation)
UV	Texture coordinates
Input (custom)	Expose a uniform to Inspector

Visual shaders compile to the same GPU code as written shaders. There is no performance difference.

Godot 4.7+: Two new spatial Input nodes — in_shadow_pass (vertex/fragment; maps to the IN_SHADOW_PASS built-in, true when the shader is being rendered in a shadow mapping pass — render objects differently in shadow maps than in the regular pass) and specular_amount (light(); maps to SPECULAR_AMOUNT — 2.0 × light_specular for OmniLight3D/SpotLight3D, 1.0 for DirectionalLight3D).

⚠️ Changed in Godot 4.7: The LinearToSRGB visual shader node no longer clamps its output to [0.0, 1.0] when using the Forward+ or Mobile renderer — HDR values above 1.0 now pass through. Graphs that relied on the implicit clamp produce different output; add an explicit Clamp node to restore the old behavior. See the 4.7 migration guide.

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6. Post-Processing Effects

The standard pattern: full-rect ColorRect with a canvas_item shader on top of the gameplay canvas. For 3D, use a WorldEnvironment Adjustment, Glow, or custom shader. For chained effects, render the world to a SubViewport then sample its texture in a final shader pass.

See references/post-processing.md for the ColorRect overlay pattern, vignette + CRT/scanline shader source, the SubViewport pipeline, and WorldEnvironment 3D post-processing notes.

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7. Compositor Effects (Godot 4.3+)

CompositorEffect runs custom render passes within Godot's render pipeline (post-tonemap or pre-tonemap). Use when ColorRect overlays aren't enough — multi-pass effects, depth-aware effects, custom AO/SSR variants. Heavier setup than a screen-space shader; reach for it only when needed.

See references/compositor-effects.md for setup, a custom CompositorEffect GDScript example, and built-in Compositor use cases.

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8. Render Modes

Render modes go on the first line after shader_type and control how the shader interacts with the rendering pipeline.

Canvas Item Render Modes

shader_type canvas_item;
render_mode unshaded;           // Ignore all lighting
render_mode light_only;         // Only visible where lit
render_mode blend_add;          // Additive blending (glow, fire)
render_mode blend_mix;          // Standard alpha blending (default)
render_mode blend_premul_alpha; // Pre-multiplied alpha

Spatial Render Modes

shader_type spatial;
render_mode unshaded;              // No lighting calculations
render_mode cull_disabled;         // Render both sides of faces
render_mode depth_draw_always;     // Always write to depth buffer
render_mode specular_toon;         // Toon specular model
render_mode diffuse_toon;          // Toon diffuse model
render_mode blend_add;             // Additive blending

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9. Stencil Buffer Effects (Godot 4.5+)

Godot 4.5 exposes stencil write/read in spatial and canvas_item shaders via stencil_write_mode, stencil_read_mode, stencil_value, etc. across all rendering backends. Enables portals, X-ray vision, outline masks, and holes-in-geometry effects that previously required compositor-level work.

See references/stencil-buffer.md for render-mode reference and the X-ray vision portal worked example.

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10. SMAA Antialiasing (Godot 4.5+)

Sub-pixel Morphological Antialiasing (SMAA 1x) is a built-in post-processing AA mode added in Godot 4.5. It produces sharper, more temporally stable results than FXAA and is less costly than MSAA for deferred-heavy scenes.

Enabling SMAA

1. Open Project Settings
2. Navigate to Rendering → Anti Aliasing → Quality
3. Set Screen Space AA to SMAA

SMAA can be combined with MSAA (for geometry edge aliasing) or used standalone. It does not require any shader code changes.

AA Mode	Sharpness	GPU cost	Ghosting
Disabled	N/A	None	None
FXAA	Low (blurry)	Very low	Low
SMAA	High	Low	Very low
TAA	Medium (slight blur)	Medium	Possible
MSAA 4x	High	High	None

When to use SMAA: Prefer SMAA over FXAA for most desktop projects — it delivers noticeably sharper text and thin edges with a similar performance profile. Combine SMAA + MSAA 2x for best quality at moderate cost.

This is an editor/export setting only — no runtime API is needed.

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11. Shader Baker — Export-time Pre-compilation (Godot 4.5+)

The Shader Baker pre-compiles all project shaders for the target platform at export time, eliminating the stutter players experience the first time a new material renders in-game — especially severe on macOS/Apple Silicon (Metal) and Windows (D3D12), where shader translation is expensive. Enable it per export preset for release builds; leave it off for development builds to keep exports fast. It operates at the Godot export pipeline level — see the export-pipeline skill for export preset configuration.

See references/shader-baker.md for enabling steps and the with/without comparison.

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12. Common Pitfalls

Symptom	Cause	Fix
Shader has no visible effect	Material not assigned or shader not saved	Check node's Material property in Inspector
Transparent parts render as black	Alpha not handled in shader	Set COLOR.a = tex.a; and use appropriate blend mode
Uniform doesn't appear in Inspector	Typo in uniform name or wrong type	Re-save the shader; check for compilation errors
Texture appears stretched/tiled	Missing repeat_enable or wrong UV scale	Add repeat_enable hint to sampler2D uniform
Shader works in editor but not in game	Screen texture uniform needs backbuffer	Use hint_screen_texture on a sampler2D uniform (Godot 4.x)
Performance drops with many shaders	Each unique shader = draw call break	Share ShaderMaterial instances; use uniforms for variation
Screen-space UV is wrong	SCREEN_UV not available in some contexts	Ensure the node is rendered in the correct viewport
Visual shader node missing	Node was renamed or removed in newer Godot version	Check Godot docs for the current node name

⚠️ Changed in Godot 4.7: textureQueryLod() is available only in the fragment shader, and Godot 4.7 enforces this with a compile error — shaders calling it from vertex() stop compiling after upgrading. Move the call into fragment(). See GH-118962.

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13. Implementation Checklist

• Shader type matches the node type (canvas_item for 2D, spatial for 3D)
• Uniforms use appropriate hints (hint_range, source_color, filter_linear_mipmap)
• Shared visual effects use the same Shader resource with separate ShaderMaterial instances
• Post-processing shaders are on a CanvasLayer (2D) or WorldEnvironment (3D), not on game objects
• TEXTURE is sampled in canvas_item shaders (otherwise sprite content is lost)
• Alpha-transparent shaders set COLOR.a correctly and use blend_mix render mode
• Animated shader parameters (dissolve, flash) are driven by Tweens or AnimationPlayer, not _process
• Screen-reading shaders use hint_screen_texture on a sampler2D uniform (Godot 4.x approach)
• Complex shaders are profiled with the Godot profiler to check GPU frame time
• Stencil effects use two-pass materials (write pass first, read pass second) with correct render priority (Godot 4.5+)
• SMAA is preferred over FXAA for desktop builds (sharper edges, similar cost) — set in Project Settings → Rendering → Anti Aliasing (Godot 4.5+)
• Shader Baker is enabled in all release export presets to eliminate first-use compilation stutters (Godot 4.5+)