Impact Glass Shader
Impact Glass Shader
What is it?
A procedural glass crack effect that creates realistic fractures using Voronoi patterns. Click anywhere on the glass – it cracks with optical refraction, blur, and glow, then automatically disappears after a set duration. Perfect for UI feedback, damage indicators, or glass-breaking mechanics.
How to use:
-
Add a ColorRect node to your scene
-
Create a new ShaderMaterial and assign the glassshatter.gdshader
-
Attach this script to the ColorRect:
extends ColorRect
## How long the crack stays visible before disappearing (seconds)
@export var crack_duration: float = 1.0
## Strength of refraction/distortion effect
@export var refraction_strength: float = 4.0
## Amount of blur around crack lines
@export var blur_amount: float = 1.2
## Tint strength of the glass material
@export var glass_tint: float = 0.06
## Glow intensity of the crack
@export var crack_glow: float = 0.8
## Number of crack points (higher = more complex cracks)
@export var point_count: int = 50
@export_range(100, 1000) var crack_radius: float = 700.0
@export_range(0.1, 3.0) var crack_thickness: float = 1.0
## Sound when cracking
@export var crack_sound: AudioStreamPlayer = null
var crack_timer: float = 0.0
var is_cracked: bool = false
func _ready():
mouse_filter = MOUSE_FILTER_STOP
_set_crack_visible(false)
_update_shader_parameters()
func _update_shader_parameters():
material.set_shader_parameter("refraction_strength", refraction_strength)
material.set_shader_parameter("blur_amount", blur_amount)
material.set_shader_parameter("glass_tint", glass_tint)
material.set_shader_parameter("crack_glow", crack_glow)
material.set_shader_parameter("point_count", point_count)
material.set_shader_parameter("crack_radius", crack_radius)
material.set_shader_parameter("crack_thickness", crack_thickness)
@warning_ignore("shadowed_variable_base_class")
func _set_crack_visible(visible: bool):
material.set_shader_parameter("show_crack", visible)
if not visible:
is_cracked = false
func _gui_input(event):
if event is InputEventMouseButton:
if event.pressed and (event.button_index == MOUSE_BUTTON_LEFT or event.button_index == MOUSE_BUTTON_RIGHT):
_show_crack(event.position)
func _show_crack(_pos: Vector2):
var screen_pos = get_viewport().get_mouse_position()
# Reset timer
crack_timer = crack_duration
is_cracked = true
# Play crack sound if assigned
if crack_sound:
crack_sound.play()
# Update shader parameters
material.set_shader_parameter("click_position", screen_pos)
material.set_shader_parameter("show_crack", true)
func _process(delta):
if is_cracked:
crack_timer -= delta
# Remove crack when timer expires
if crack_timer <= 0.0:
_set_crack_visible(false)
## Public API: Manually trigger a crack
func trigger_crack():
_show_crack(Vector2.ZERO)
## Public API: Check if glass is currently cracked
func is_cracked_state() -> bool:
return is_cracked
Optional Features:
-
Optional: Add an AudioStreamPlayer child and assign it to crack_sound
-
Adjust parameters in the inspector to control crack duration, complexity, and visual style
- That’s it! Click anywhere and watch the glass crack.
Shader code
shader_type canvas_item;
uniform sampler2D SCREEN_TEXTURE : hint_screen_texture, filter_linear_mipmap;
uniform vec2 click_position = vec2(0.0, 0.0);
uniform bool show_crack = false;
uniform float crack_thickness = 0.25;
uniform int point_count = 30;
uniform float crack_intensity = 1.0;
uniform float refraction_strength = 5.0;
uniform float blur_amount = 2.0;
uniform float glass_tint = 0.1;
uniform float crack_glow = 0.5;
uniform vec4 crack_color : source_color = vec4(0.118, 0.118, 0.118, 0.588);
uniform float heal_amount = 0.0;
// random
float random(vec2 st) {
return fract(sin(dot(st.xy, vec2(12.9898,78.233))) * 43758.5453123);
}
// noise
float noise(vec2 st) {
vec2 i = floor(st);
vec2 f = fract(st);
float a = random(i);
float b = random(i + vec2(1.0, 0.0));
float c = random(i + vec2(0.0, 1.0));
float d = random(i + vec2(1.0, 1.0));
vec2 u = f * f * (3.0 - 2.0 * f);
return mix(mix(a, b, u.x), mix(c, d, u.x), u.y);
}
// voronoi edge
float voronoi_edge(vec2 uv, int count, out float min_dist, out float second_dist, out vec2 nearest_point) {
min_dist = 1000.0;
second_dist = 1000.0;
nearest_point = uv;
for (int i = 0; i < 50; i++) {
if (i >= count) break;
float t = float(i) / float(count - 1);
float max_radius = 500.0;
float r = max_radius * pow(t, 1.2);
float angle = random(vec2(float(i), click_position.x + click_position.y)) * 6.28318;
angle += noise(vec2(float(i) * 0.1, 0.0)) * 1.0;
vec2 point = click_position + vec2(cos(angle), sin(angle)) * r;
float dist = distance(uv, point);
if (dist < min_dist) {
second_dist = min_dist;
min_dist = dist;
nearest_point = point;
} else if (dist < second_dist) {
second_dist = dist;
}
}
return second_dist - min_dist;
}
void fragment() {
vec2 uv = FRAGCOORD.xy;
vec2 screen_uv = SCREEN_UV;
// --- BASE GLASS EFFECT (applies to entire glass surface) ---
// Add subtle constant refraction to whole glass
vec2 base_refraction = vec2(
noise(uv * 0.01) * 0.0005,
noise(uv * 0.01 + 100.0) * 0.0005
);
vec2 glass_uv = screen_uv + base_refraction;
vec4 glass_color = texture(SCREEN_TEXTURE, glass_uv);
// Add subtle blur to entire glass
vec4 blur_col = vec4(0.0);
float total = 0.0;
int samples = 1; // Light blur on whole glass
for (int x = -samples; x <= samples; x++) {
for (int y = -samples; y <= samples; y++) {
vec2 offset = vec2(float(x), float(y)) * 0.0005;
blur_col += texture(SCREEN_TEXTURE, glass_uv + offset);
total += 1.0;
}
}
blur_col /= total;
// Apply glass tint to entire surface
glass_color = mix(blur_col, vec4(0.8, 0.9, 1.0, 1.0), glass_tint * 0.5);
// --- CRACK EFFECT (only if showing) ---
if (show_crack) {
float min_dist, second_dist;
vec2 nearest_point;
float edge_value = voronoi_edge(uv, point_count, min_dist, second_dist, nearest_point);
float is_edge = 1.0 - smoothstep(0.0, crack_thickness, edge_value);
float crack_noise = noise(uv * 0.05) * 0.2;
is_edge = clamp(is_edge + crack_noise * 0.1, 0.0, 1.0);
// Apply healing
float heal_factor = 1.0 - heal_amount;
is_edge = is_edge * heal_factor;
float dissolve = smoothstep(heal_amount - 0.2, heal_amount + 0.3, is_edge);
vec2 shard_dir = normalize(uv - nearest_point);
float shard_strength = 1.0 - smoothstep(0.0, 250.0, min_dist);
// Enhanced refraction near cracks
float current_refraction = refraction_strength * (1.0 - heal_amount * 0.8);
vec2 magnify = (uv - nearest_point) * 0.0008 * shard_strength;
vec2 refracted_uv = screen_uv
+ shard_dir * current_refraction * 0.001 * shard_strength
+ magnify;
// Stronger blur near cracks
vec4 crack_blur = vec4(0.0);
float crack_total = 0.0;
int crack_samples = int(blur_amount);
for (int x = -crack_samples; x <= crack_samples; x++) {
for (int y = -crack_samples; y <= crack_samples; y++) {
vec2 offset = vec2(float(x), float(y)) * 0.001;
crack_blur += texture(SCREEN_TEXTURE, refracted_uv + offset);
crack_total += 1.0;
}
}
crack_blur /= crack_total;
crack_blur = mix(crack_blur, vec4(0.8, 0.9, 1.0, 1.0), glass_tint);
// Mix between base glass and crack effect based on distance to crack
float mix_factor = smoothstep(0.0, 150.0, min_dist);
mix_factor = 1.0 - mix_factor;
mix_factor = mix_factor * (1.0 - heal_amount);
glass_color = mix(glass_color, crack_blur, mix_factor);
// Crack glow
float glow = is_edge * crack_glow * crack_intensity * (1.0 - heal_amount);
float dist_center = distance(uv, click_position);
float inner_glow = (1.0 - smoothstep(0.0, 80.0, dist_center)) * 0.3 * (1.0 - heal_amount);
float crack_light = glow + inner_glow;
glass_color.rgb += crack_color.rgb * crack_light;
if (dissolve < 0.1) {
// Keep base glass effect even when crack is healing
glass_color = mix(glass_color, glass_color, 0.0);
}
}
COLOR = vec4(glass_color.rgb, 1.0);
}Live Preview
