godot-shaders-basics

name	godot-shaders-basics
description	Expert blueprint for shader programming (visual effects, post-processing, material customization) using Godot's GLSL-like shader language. Covers canvas_item (2D), spatial (3D), uniforms, built-in variables, and performance. Use when implementing custom effects OR stylized rendering. Keywords shader, GLSL, fragment, vertex, canvas_item, spatial, uniform, UV, COLOR, ALBEDO, post-processing.

Shader Basics

Fragment/vertex shaders, uniforms, and built-in variables define custom visual effects.

Available Scripts

vfx_port_shader.gdshader

Expert shader template with parameter validation and common effect patterns.

shader_parameter_animator.gd

Runtime shader uniform animation without AnimationPlayer - for dynamic effects.

NEVER Do in Shaders

• NEVER use expensive operations in fragment() — pow(), sqrt(), sin() on every pixel? 1920x1080 = 2M calls/frame = lag. Pre-calculate OR use texture lookups.
• NEVER forget to normalize vectors — reflect(direction, normal) without normalization? Wrong reflections + rendering artifacts. ALWAYS normalize direction vectors.
• NEVER use if/else for branching — GPUs hate branching (SIMD architecture). Use mix(), step(), smoothstep() for conditional logic.
• NEVER modify UV without bounds check — UV.x += 10.0 goes outside 0-1 range? Texture sampling breaks. Use fract() OR clamp().
• NEVER use TIME without delta — COLOR.a = sin(TIME) runs at variable speed on different framerates. Use TIME * speed_factor for consistent animation.
• NEVER forget hint_source_color for colors — uniform vec4 tint without hint? Inspector shows raw floats. Use uniform vec4 tint : source_color for color picker.

---

shader_type canvas_item;

void fragment() {
    // Get texture color
    vec4 tex_color = texture(TEXTURE, UV);
    
    // Tint red
    COLOR = tex_color * vec4(1.0, 0.5, 0.5, 1.0);
}

Apply to Sprite:

1. Select Sprite2D node
2. Material → New ShaderMaterial
3. Shader → New Shader
4. Paste code

Common 2D Effects

Dissolve Effect

shader_type canvas_item;

uniform float dissolve_amount : hint_range(0.0, 1.0) = 0.0;
uniform sampler2D noise_texture;

void fragment() {
    vec4 tex_color = texture(TEXTURE, UV);
    float noise = texture(noise_texture, UV).r;
    
    if (noise < dissolve_amount) {
        discard;  // Make pixel transparent
    }
    
    COLOR = tex_color;
}

Wave Distortion

shader_type canvas_item;

uniform float wave_speed = 2.0;
uniform float wave_amount = 0.05;

void fragment() {
    vec2 uv = UV;
    uv.x += sin(uv.y * 10.0 + TIME * wave_speed) * wave_amount;
    
    COLOR = texture(TEXTURE, uv);
}

Outline

shader_type canvas_item;

uniform vec4 outline_color : source_color = vec4(0.0, 0.0, 0.0, 1.0);
uniform float outline_width = 2.0;

void fragment() {
    vec4 col = texture(TEXTURE, UV);
    vec2 pixel_size = TEXTURE_PIXEL_SIZE * outline_width;
    
    float alpha = col.a;
    alpha = max(alpha, texture(TEXTURE, UV + vec2(pixel_size.x, 0.0)).a);
    alpha = max(alpha, texture(TEXTURE, UV + vec2(-pixel_size.x, 0.0)).a);
    alpha = max(alpha, texture(TEXTURE, UV + vec2(0.0, pixel_size.y)).a);
    alpha = max(alpha, texture(TEXTURE, UV + vec2(0.0, -pixel_size.y)).a);
    
    COLOR = mix(outline_color, col, col.a);
    COLOR.a = alpha;
}

3D Shaders

Basic 3D Shader

shader_type spatial;

void fragment() {
    ALBEDO = vec3(1.0, 0.0, 0.0);  // Red material
}

Toon Shading (Cel-Shading)

shader_type spatial;

uniform vec3 base_color : source_color = vec3(1.0);
uniform int color_steps = 3;

void light() {
    float NdotL = dot(NORMAL, LIGHT);
    float stepped = floor(NdotL * float(color_steps)) / float(color_steps);
    
    DIFFUSE_LIGHT = base_color * stepped;
}

Screen-Space Effects

Vignette

shader_type canvas_item;

uniform float vignette_strength = 0.5;

void fragment() {
    vec4 color = texture(TEXTURE, UV);
    
    // Distance from center
    vec2 center = vec2(0.5, 0.5);
    float dist = distance(UV, center);
    
    float vignette = 1.0 - dist * vignette_strength;
    
    COLOR = color * vignette;
}

Uniforms (Parameters)

// Float slider
uniform float intensity : hint_range(0.0, 1.0) = 0.5;

// Color picker
uniform vec4 tint_color : source_color = vec4(1.0);

// Texture
uniform sampler2D noise_texture;

// Access in code:
material.set_shader_parameter("intensity", 0.8)

Built-in Variables

2D (canvas_item):

• UV - Texture coordinates (0-1)
• COLOR - Output color
• TEXTURE - Current texture
• TIME - Time since start
• SCREEN_UV - Screen coordinates

3D (spatial):

• ALBEDO - Base color
• NORMAL - Surface normal
• ROUGHNESS - Surface roughness
• METALLIC - Metallic value

Best Practices

1. Use Uniforms for Tweaking

// ✅ Good - adjustable
uniform float speed = 1.0;

void fragment() {
    COLOR.r = sin(TIME * speed);
}

// ❌ Bad - hardcoded
void fragment() {
    COLOR.r = sin(TIME * 2.5);
}

2. Optimize Performance

// Avoid expensive operations in fragment shader
// Pre-calculate values when possible
// Use textures for complex patterns

3. Comment Shaders

// Water wave effect
// Creates horizontal distortion based on sine wave
uniform float wave_amplitude = 0.02;

Reference

• Godot Docs: Shading Language
• Godot Docs: Your First Shader

Related

• Master Skill: godot-master