Impact Glass Shader

Interactive procedural glass crack effect for Godot 4.

Overview

A production-ready shader implementation that generates realistic glass fracture patterns using procedural Voronoi diagrams. Features dynamic distortion, optical refraction effects, and configurable crack propagation for interactive UI feedback and game mechanics.

Key Features:

• Procedurally generated Voronoi-based crack patterns
• Optical refraction and dynamic blur effects
• Configurable crack propagation and appearance
• Auto-reset timing with manual control options
• Optimized for real-time rendering across platforms

Table of Contents

• Features
• Architecture
• Setup
• Configuration
• API Reference
• Implementation Details
• Performance
• Troubleshooting
• License

Features

Feature	Description
Procedural Crack Generation	Voronoi-based fracture patterns radiating from impact point
Optical Refraction	Light bending effect simulating broken glass surfaces
Dynamic Blur	Depth-of-field effect concentrated near crack lines
Glass Material Properties	Subtle tint and refraction across entire surface
Impact Detection	Instant crack generation at specified coordinates
Configurable Duration	Automatic reset with adjustable visibility window
Audio Integration	Built-in support for impact sound effects
Parameter Control	10+ adjustable parameters for customization

Use Cases

Scenario	Application
User Interface	Breaking interface elements for visual feedback
Game Mechanics	Glass breaking targets, destructible shields
Damage Visualization	Impact indicators, health state transitions
Interactive Art	Installation pieces, procedural animations
Transition Effects	Scene changes, screen shatters

Architecture

System Overview

graph TD
    A["Input: Mouse Position"] -->|Update| B["Shader Parameters"]
    B -->|Sample| C["Base Glass Texture"]
    C -->|Generate| D["Voronoi Pattern"]
    D -->|Calculate| E["Crack Detection"]
    E -->|Apply| F["Distortion & Blur"]
    F -->|Render| G["Optical Effects"]
    G -->|Output| H["Final Composited Texture"]

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Rendering Pipeline

The shader processes screen texture through multiple stages:

graph LR
    A["Screen Texture"] -->|1| B["Base Glass<br/>Refraction & Tint"]
    B -->|2| C["Crack Detection<br/>Voronoi Edges"]
    C -->|3| D["Distortion<br/>Enhanced Refraction"]
    D -->|4| E["Blur Effect<br/>Shard Mapping"]
    E -->|5| F["Glow & Composition<br/>Final Blend"]
    F -->|Output| G["Display"]
    
    style A fill:#e1f5ff
    style G fill:#c8e6c9

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Class and Script Structure

classDiagram
    class ColorRect {
        +material: ShaderMaterial
        +size: Vector2
    }
    
    class GlassShader {
        +crack_duration: float
        +refraction_strength: float
        +blur_amount: float
        +point_count: int
        +crack_radius: float
        +trigger_crack()
        +is_cracked_state() bool
        -_set_crack_visible(bool)
    }
    
    class AudioStreamPlayer {
        +stream: AudioStream
        +play()
    }
    
    class ShaderMaterial {
        +shader: Shader
        +set_shader_parameter()
    }
    
    ColorRect --|> GlassShader
    ColorRect --|> ShaderMaterial
    GlassShader --|> AudioStreamPlayer

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Setup

Installation

1. Add the shader file to your project:

   res://shader/glassshatter.gdshader
   

2. Create a ColorRect node:

   var glass = ColorRect.new()
   glass.size = get_viewport_rect().size
   add_child(glass)

3. Assign the shader material:

   var material = ShaderMaterial.new()
   material.shader = preload("res://shader/glassshatter.gdshader")
   glass.material = material

4. Attach the control script:

   glass.set_script(preload("res://scripts/ui_2.gd"))

Basic Integration

extends ColorRect

func _ready():
    # Configure crack appearance
    crack_duration = 1.0
    refraction_strength = 4.0
    blur_amount = 1.2
    point_count = 50
    
    # Optional: attach sound effect
    var audio = AudioStreamPlayer.new()
    audio.stream = preload("res://assets/stu9-glass-crack-363162.mp3")
    add_child(audio)
    crack_sound = audio

func _input(event: InputEvent):
    if event is InputEventMouseButton and event.pressed:
        trigger_crack()

Configuration

Script Parameters (ui_2.gd)

Parameter	Type	Default	Range	Description
crack_duration	float	1.0	0.1-10.0	Visibility window before auto-reset (seconds)
refraction_strength	float	4.0	0.0-10.0	Intensity of light distortion around cracks
blur_amount	float	1.2	0.0-5.0	Blur radius applied near crack lines
glass_tint	float	0.06	0.0-1.0	Glass surface tint intensity
crack_glow	float	0.8	0.0-2.0	Brightness multiplier for crack lines
point_count	int	50	20-100	Number of seed points for Voronoi pattern
crack_radius	float	700.0	100-2000	Maximum propagation distance from impact
crack_thickness	float	1.0	0.1-5.0	Visual width of crack lines
crack_color	Color	Black	—	RGBA color of rendered cracks
crack_sound	AudioStreamPlayer	null	—	Optional audio feedback on impact

Shader Uniforms (glassshatter.gdshader)

Uniform	Type	Description
click_position	vec2	World/viewport coordinates of impact point
show_crack	bool	Toggle crack pattern visibility
crack_intensity	float	Normalized crack strength (0.0-1.0)
crack_color	vec4	Crack line color with alpha channel
heal_amount	float	Reserved for future healing mechanics

Preset Configurations

Subtle Glass Effect

refraction_strength = 1.5
blur_amount = 0.5
glass_tint = 0.02
crack_glow = 0.4
point_count = 30

Aggressive Damage

refraction_strength = 6.0
blur_amount = 2.5
glass_tint = 0.1
crack_glow = 1.5
point_count = 80
crack_thickness = 2.0

Mobile Optimized

point_count = 25
blur_amount = 0.8
refraction_strength = 2.0
crack_radius = 500.0

API Reference

Public Methods

trigger_crack()

Initiates crack generation at current mouse position.

func trigger_crack() -> void

Example:

glass.trigger_crack()

is_cracked_state() -> bool

Returns whether glass is currently displaying a crack pattern.

func is_cracked_state() -> bool

Example:

if glass.is_cracked_state():
    print("Glass is damaged")

_set_crack_visible(visible: bool)

Manually control crack visibility without affecting timer.

func _set_crack_visible(visible: bool) -> void

Example:

glass._set_crack_visible(false)  # Hide crack immediately

Signal Integration

Extend the base script to implement custom signals:

signal crack_triggered(position: Vector2)
signal crack_disappeared

func _show_crack(pos: Vector2):
    crack_triggered.emit(pos)
    # Additional logic here

Implementation Details

Voronoi-Based Crack Generation

The core algorithm generates realistic fracture patterns using Voronoi diagram principles.

Algorithm Overview

graph TD
    A["1. Click Event"] -->|Get Position| B["2. Generate Seed Points"]
    B -->|Radial Spread| C["3. Calculate Point Distribution"]
    C -->|For Each Pixel| D["4. Find Nearest & 2nd Nearest Points"]
    D -->|Distance Difference| E["5. Compute Voronoi Edges"]
    E -->|Smoothstep| F["6. Render Crack Lines"]
    F -->|Add Noise| G["7. Apply Organic Variation"]
    G -->|Composite| H["8. Output Crack Pattern"]

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Voronoi Edge Detection

// Core Voronoi calculation
float voronoi_edge(vec2 uv, vec2 points[MAX_POINTS]) {
    float min_dist = distance(uv, points[0]);
    float second_dist = distance(uv, points[1]);
    
    for (int i = 1; i < point_count; i++) {
        float dist = distance(uv, points[i]);
        if (dist < min_dist) {
            second_dist = min_dist;
            min_dist = dist;
        } else if (dist < second_dist) {
            second_dist = dist;
        }
    }
    
    // Edges appear where two regions meet
    return second_dist - min_dist;
}

Radial Point Distribution

Points are distributed radially with density falloff:

graph LR
    A["Impact Point"] -->|Dense| B["Inner Region<br/>0-200px"]
    B -->|Medium| C["Mid Region<br/>200-500px"]
    C -->|Sparse| D["Outer Region<br/>500-700px"]
    
    style A fill:#ffcdd2
    style B fill:#ffccbc
    style C fill:#ffe0b2
    style D fill:#fff9c4

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Shader Processing Stages

1. Base Glass Layer

• Applies subtle refraction using noise-based offsets
• Mixes screen texture with tint color (0.85, 0.9, 0.98 RGB)
• Performs 3x3 blur sampling for smooth appearance

2. Crack Detection

• Calculates Voronoi edges from generated seed points
• Applies smoothstep for edge thickness control
• Adds procedural noise for organic irregularity

3. Distortion & Blur

• Enhances refraction intensity near crack lines
• Maps blur direction based on shard orientation
• Applies variable blur strength proportional to distance from crack

4. Glow & Composition

• Adds glow intensity to crack lines
• Applies central impact glow effect
• Blends base glass with crack regions using smooth transitions

Mathematical Operations

graph TD
    A["Input: UV Coordinates"] -->|Normalize| B["Adjust for Click Position"]
    B -->|Generate| C["Random Points via Hash"]
    C -->|Calculate Distance| D["Euclidean Distance Formula"]
    D -->|Sort| E["Find Min & Second Min"]
    E -->|Difference| F["Distance Delta"]
    F -->|Smoothstep| G["0-1 Edge Value"]
    G -->|Multiply| H["Final Crack Intensity"]
    H -->|Output| I["Crack Layer"]

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Performance

Computational Complexity

Component	Complexity	Impact
Point Generation	O(n)	Linear in point count
Distance Calculation	O(n²)	Quadratic per pixel
Blur Operations	O(k²)	Quadratic in kernel size
Overall Per-Frame	O(n² × pixels)	Dominant factor

Platform-Specific Optimization

Desktop

point_count = 75
blur_amount = 2.5
refraction_strength = 5.0

• Supports high-resolution displays
• Handles intensive shader calculations
• Smooth 60+ FPS performance

Mobile/Web

point_count = 30
blur_amount = 0.8
refraction_strength = 2.5

• Optimized for battery efficiency
• Reduced calculation overhead
• Stable 30-60 FPS

Low-End Hardware

point_count = 15
blur_amount = 0.4
refraction_strength = 1.5

• Minimal shader workload
• Simplified crack pattern
• Maintains 30 FPS baseline

Optimization Techniques

1. Point Count Reduction: Lower point counts produce coarser crack patterns with 4x performance improvement

2. Blur Kernel Optimization: Use directional blur instead of full 2D kernel for 50% reduction in sampling operations

3. Conditional Rendering: Only compute expensive operations when show_crack is true

4. Mip-mapping: Pre-compute noise textures at multiple resolutions

Profiling Recommendations

# Enable Godot's built-in profiler
Performance.get_monitor(Performance.TIME_PHYSICS_PROCESS)

# Monitor shader execution time
var start = Time.get_ticks_msec()
# Trigger crack
var elapsed = Time.get_ticks_msec() - start
print("Crack generation: %dms" % elapsed)

File Structure

Glass-Crack-Shader/
├── assets/
│   ├── stu9-glass-crack-363162.mp3      # Crack impact audio
│   └── stu9-glass-crack-363162.mp3.import
├── scene/
│   └── final.tsn                         # Demo scene
├── scripts/
│   └── ui_2.gd                           # Control script
├── shader/
│   └── glassshatter.gdshader             # Shader implementation
├── LICENSE                               # MIT License
├── project.godot                         # Godot project configuration
└── README.md                             # Documentation

Troubleshooting

Common Issues and Solutions

Issue	Cause	Solution
No crack appears	show_crack disabled or wrong coordinate space	Verify show_crack = true and coordinates are in viewport space
Cracks look blocky	Insufficient point count or large thickness	Increase point_count to 50-80, reduce crack_thickness
Performance degradation	Excessive point count or blur radius	Reduce point_count to 30-40, limit blur_amount to 1.0-1.5
Audio not playing	Missing stream assignment	Assign valid AudioStream to crack_sound before triggering
Cracks at wrong position	Coordinate system mismatch	Use get_viewport().get_mouse_position() consistently
Uneven crack distribution	Poor hash function or seed points	Verify random point generation uses distinct seeds
Shader compilation error	Missing GLSL extension or syntax	Check shader compiler output in Godot console

Debug Logging

# Enable detailed debugging
extends ColorRect

func _ready():
    set_process_input(true)
    print("Glass shader initialized")

func _show_crack(pos: Vector2):
    print("Crack triggered at: %v" % pos)
    print("Current parameters: point_count=%d, duration=%.2f" % [point_count, crack_duration])
    trigger_crack()

func _on_crack_disappear():
    print("Crack animation completed")

Performance Debugging

# Measure shader performance
func benchmark_crack():
    var times = []
    for i in range(10):
        var start = Time.get_ticks_msec()
        trigger_crack()
        await get_tree().process_frame
        times.append(Time.get_ticks_msec() - start)
    
    var avg = times.reduce(func(a, b): return a + b) / times.size()
    print("Average crack generation time: %.2fms" % avg)

Advanced Usage

Custom Crack Colors

# Dark transparent cracks
material.set_shader_parameter("crack_color", Color(0.1, 0.1, 0.1, 0.8))

# Bright white cracks with transparency
material.set_shader_parameter("crack_color", Color(1.0, 1.0, 1.0, 0.6))

# Colored tint (blue glass cracks)
material.set_shader_parameter("crack_color", Color(0.4, 0.6, 1.0, 0.9))

Dynamic Parameter Tweening

# Gradually increase refraction
var tween = create_tween()
tween.tween_method(func(val): refraction_strength = val, 
                   2.0, 6.0, 0.5)

Procedural Crack Events

# Trigger multiple cracks in sequence
func cascade_cracks():
    for i in range(3):
        trigger_crack()
        await get_tree().create_timer(0.3).timeout

License

This project is licensed under the MIT License.

MIT License

Copyright (c) 2026 Lord0Sanz

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

See LICENSE file for complete terms.

Contributing

Contributions are welcome. Please ensure:

1. Code follows Godot style guidelines
2. Shader changes are documented
3. Performance impact is evaluated
4. All parameters are tested across platforms

Support & Resources

• Godot Engine: godotengine.org
• Shader Documentation: Impact Glass Shader

Creator

PROJEKTSANSSTUDIOS

• GitHub: github.com/Lord0Sanz
• itch.io: projekt-sans-studios.itch.io
• Godot Shader: PROJEKTSANSSTUDIOS

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Version: 1.0
Last Updated: 2026
Godot Compatibility: 4.6 and later