Shader Basics

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").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](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](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.

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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](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](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](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 your project's shaders for the target platform at export time rather than at runtime. This eliminates the stutter players experience the first time a new material renders in-game, which is especially severe on macOS/Apple Silicon (Metal) and D3D12 (Windows) where shader translation is expensive.

Enabling Shader Baker

Shader baking is configured per export preset:

1. Open Project → Export
2. Select (or create) an export preset for your target platform
3. In the preset options, locate Shader Baker and set it to Enabled
4. Export as normal — baked shader cache files are bundled into the export

What It Does

| Stage | Without Shader Baker | With Shader Baker | |-------|----------------------|-------------------| | Export | Fast | Slower (compiles shaders) | | First material use in game | Stutter (compiles shader on GPU) | Instant (pre-compiled) | | Subsequent loads | Cached after first run | Always cached |

> When to use: Enable Shader Baker for all release builds targeting desktop (macOS, Windows/D3D12) or mobile. The extra export time is worth the stutter-free player experience. For development builds, leave it off to keep iteration fast.

Shader Baker operates at the Godot export pipeline level — see the export-pipeline skill for how to configure export presets.

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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 |

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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+)

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: jame581
• Source: jame581/GodotPrompter
• License: MIT

Install and usage instructions live in the source repository linked above.