jame581 / 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.

1. Core Concepts

Shader Types

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.

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)

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)

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

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);

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.

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.

5. Visual Shaders

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

When to Use Visual Shaders

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

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).

⚠‹VARIATION SELECTOR U+FE0F› 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.

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.

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.

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

9. Stencil Buffer Effects (Godot 4.5+)

Godot 4.5 exposes stencil write/read in spatial shaders via the stencil_mode statement (stencil_mode write, 1; / stencil_mode read, compare_equal, 1;) and on StandardMaterial3D (Stencil: Outline / X-Ray / Custom), across all rendering backends. canvas_item shaders have no stencil modes. 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 the stencil_mode reference and the X-ray vision portal worked example.

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 clearer results than FXAA at a slightly higher performance cost, and is much cheaper than MSAA.

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.

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

The project setting is read at startup only. To switch at runtime set get_viewport().screen_space_aa = Viewport.SCREEN_SPACE_AA_SMAA (C#: GetViewport().ScreenSpaceAA = Viewport.ScreenSpaceAAEnum.Smaa). Forward+ and Mobile only — not Compatibility.

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

The Shader Baker converts project shaders to the target driver's format at export time, which shortens first-launch load — most on macOS/iOS (Metal) and Windows (D3D12), where that conversion is slow. It does not remove pipeline-compilation stutter the first time a material renders, works only on the Forward+ and Mobile renderers, and bakes only for drivers the exporting machine's OS supports. Enable it per export preset for release builds; leave it off for development.

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

12. Common Pitfalls

⚠‹VARIATION SELECTOR U+FE0F› 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.

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, slightly higher cost) — set in Project Settings → Rendering → Anti Aliasing (Godot 4.5+)
• [ ] Shader Baker is enabled in release presets for D3D12 and Metal targets to shorten first-launch load (Forward+/Mobile only; Godot 4.5+)