Decal shader (+Y_Fading +Particle Alpha SCISSOR Treshold)
This is a shader I’ve created for a tutorial in YT, but i decided to share it, since it might be usefull for some people..
In the tutorial i’ve used it to make a dynamic blood stains trace.. but it also works for other stuff..
i’ll post the tutorial link later on.. basically to make it work, create a particle system, use a looking up plane with size 4×4 .. and create an alpha curve in the particles process material.. then add some textures and color..
Shader code
// Credits: Shader based on OlisUnfinishedProjects 4.0 Decal Shader
// https://godotshaders.com/shader/decal-shader-4-0-port/
// https://stackoverflow.com/questions/32227283/getting-world-position-from-depth-buffer-value
// LeLu (forked 29/10/25) -> New dynamic decal based on particles with height fading
shader_type spatial;
render_mode world_vertex_coords, blend_mix, cull_back, diffuse_lambert, specular_schlick_ggx;
uniform vec2 Scale = vec2(1.000000, 1.000000);
uniform sampler2D Color_1D_gradient : source_color, repeat_disable;
uniform sampler2D Albedo : source_color, repeat_disable;
uniform sampler2D Normal : source_color, hint_normal, repeat_disable;
uniform sampler2D Roughtness : source_color, hint_default_white, repeat_disable;
uniform sampler2D DEPTH_TEXTURE: hint_depth_texture;
uniform float cube_half_size = 0.5;
// Y-axis fade controls
uniform bool enable_y_fade = false; // Toggle for fade effect
uniform float fade_start = 0.3; // Where fading begins (0-1)
uniform float fade_end = 0.7; // Where fading ends (0-1)
uniform float fade_power = 2.0; // Curve sharpness
uniform bool use_red_channel_as_alpha = false;
varying mat4 INV_MODEL_MATRIX;
uniform float normal_intensity = 1.0;
void vertex(){
INV_MODEL_MATRIX = inverse(MODEL_MATRIX);
}
vec3 world_pos_from_depth(float depth, vec2 screen_uv, mat4 inverse_proj, mat4 inverse_view) {
float z = depth;
vec4 clipSpacePosition = vec4(screen_uv * 2.0 - 1.0, z, 1.0);
vec4 viewSpacePosition = inverse_proj * clipSpacePosition;
viewSpacePosition /= viewSpacePosition.w;
vec4 worldSpacePosition = inverse_view * viewSpacePosition;
return worldSpacePosition.xyz;
}
float smooth_fade(float y_pos) {
// Normalize Y position (-0.5 to 0.5) -> (0 to 1)
float normalized_y = clamp((y_pos + cube_half_size) / (2.0 * cube_half_size), 0.0, 1.0);
// Calculate fade factor
float fade_factor = smoothstep(fade_start, fade_end, normalized_y);
fade_factor = pow(fade_factor, fade_power);
return 1.0 - fade_factor;
}
void fragment() {
float depth = texture(DEPTH_TEXTURE, SCREEN_UV).x;
vec3 world_pos = world_pos_from_depth(depth, SCREEN_UV, INV_PROJECTION_MATRIX, (INV_VIEW_MATRIX));
vec4 test_pos = (INV_MODEL_MATRIX * vec4(world_pos, 1.0));
if (abs(test_pos.x) > cube_half_size || abs(test_pos.y) > cube_half_size || abs(test_pos.z) > cube_half_size) {
discard;
}
vec2 NEW_UV = (test_pos.xz) + 0.5;
vec4 n_out3p0 = texture(Albedo, NEW_UV * Scale);
vec3 normal_map = texture(Normal, NEW_UV * Scale).rgb;
float rought_map = texture(Roughtness, NEW_UV * Scale).r;
// Default fade factor (1.0 means no fade)
float y_fade = 1.0;
// Only calculate fade if enabled
if (enable_y_fade) {
y_fade = smooth_fade(test_pos.y);
if (y_fade <= 0.0) {
discard;
}
}
vec3 colored_texture = texture(Color_1D_gradient ,vec2(n_out3p0.r) * y_fade).rgb;
float alphad = 0.0;
if (use_red_channel_as_alpha){
alphad = n_out3p0.r;}
else{ alphad = n_out3p0.a;}
// Apply fade to all channels (or full strength if fade disabled)
ALBEDO = colored_texture * COLOR.rgb;
ALPHA = alphad * y_fade ;
ALPHA_SCISSOR_THRESHOLD = COLOR.a;
NORMAL = normal_map;
NORMAL_MAP_DEPTH = normal_intensity;
ROUGHNESS = rought_map;
METALLIC = 0.1;
}
// Credits: Shader based on OlisUnfinishedProjects 4.0 Decal Shader
// https://godotshaders.com/shader/decal-shader-4-0-port/
// https://stackoverflow.com/questions/32227283/getting-world-position-from-depth-buffer-value
