# Raymarched 3D Noise Decal

Example usage in the demo project. For clarity the SDF noise implementation in the project is in a separate include file, but the code here has been merged together.

``````shader_type spatial;

// http://iquilezles.org/www/articles/smin/smin.htm
float smin( float a, float b, float k )
{
float h = max(k-abs(a-b),0.0);
return min(a, b) - h*h*0.25/k;
}

// http://iquilezles.org/www/articles/smin/smin.htm
float smax( float a, float b, float k )
{
float h = max(k-abs(a-b),0.0);
return max(a, b) + h*h*0.25/k;
}

// https://iquilezles.org/www/articles/fbmsdf/fbmsdf.htm
float sph( vec3 i, vec3 f, vec3 c )
{
// random radius at grid vertex i+c (please replace this hash by
// something better if you plan to use this for a real application)
vec3  p = 17.0*fract( (i+c)*0.3183099+vec3(0.11,0.17,0.13) );
float w = fract( p.x*p.y*p.z*(p.x+p.y+p.z) );
float r = 0.7*w*w;
// distance to sphere at grid vertex i+c
return length(f-c) - r;
}

// https://iquilezles.org/www/articles/fbmsdf/fbmsdf.htm
float sdBase( in vec3 p )
{
vec3 i = floor(p);
vec3 f = fract(p);
return min(min(min(sph(i,f,vec3(0,0,0)),
sph(i,f,vec3(0,0,1))),
min(sph(i,f,vec3(0,1,0)),
sph(i,f,vec3(0,1,1)))),
min(min(sph(i,f,vec3(1,0,0)),
sph(i,f,vec3(1,0,1))),
min(sph(i,f,vec3(1,1,0)),
sph(i,f,vec3(1,1,1)))));
}

// https://iquilezles.org/www/articles/fbmsdf/fbmsdf.htm
float sdFbm(
in vec3 p,
in int detail,
in float rough,
in float inflate,
in float smooth_fac,
in float d)
{
float s = 1.0;
for( int i=0; i < min(int(detail), 12); i++ )
{
float n = s*sdBase(p);

n = smax(n,d - inflate*s, smooth_fac*s );
d = smin(n,d      , smooth_fac*s );

p = mat3(vec3( 0.00, 1.60, 1.20),
vec3(-1.60, 0.72,-0.96),
vec3(-1.20,-0.96, 1.280))*p;
s = rough*s;
}
return d;
}

render_mode depth_test_disabled, cull_front;

uniform sampler2D depth_tex : hint_depth_texture;

group_uniforms Color;

uniform float col_distance_scale = 1.0;
uniform vec3 col_near : source_color = vec3(1.0);
uniform vec3 col_far : source_color = vec3(0.0);
uniform float emission_boost = 1.0;

group_uniforms;

group_uniforms SDFNoise;

uniform float sphere_radius = 0.5;

uniform float noise_scale = 1.0;
uniform int detail = 4;
uniform float rough = 0.5;
uniform float inflate = 0.1;
uniform float smooth_fac = 0.2;

uniform float step_mult = 1.0;

group_uniforms;

mat3 y_rot(float angle) {
return mat3(
vec3(cos(angle), 0.0, -sin(angle)),
vec3(0.0, 1.0, 0.0),
vec3(sin(angle), 0.0, cos(angle))
);
}

float sdf_map(vec3 pos) {
float sphere_dist = length(pos) - sphere_radius;

vec3 noise_offset = vec3(0.0, -TIME * 0.1, 0.0);

pos = y_rot(pos.y * 10.0) * pos;

pos = pos * noise_scale + noise_offset;

sphere_dist = sdFbm(pos, detail, rough, inflate, smooth_fac, sphere_dist);

return -sphere_dist;
}

void fragment() {
float depth = textureLod(depth_tex, SCREEN_UV, 0.0).r;
vec4 upos = INV_PROJECTION_MATRIX * vec4(SCREEN_UV * 2.0 - 1.0, depth, 1.0);
vec3 pixel_position = upos.xyz / upos.w;

vec4 wpos = INV_VIEW_MATRIX * (upos / upos.w);

vec3 obj_position = -(inverse(MODEL_MATRIX) * wpos).xyz;
vec3 obj_view_vec = inverse(mat3(MODEL_MATRIX)) * mat3(INV_VIEW_MATRIX) * VIEW;

vec3 view_dir = normalize(obj_view_vec);

vec3 cur_pos = obj_position;
for (int i = 0; i < 50; i++) {

float offset = sdf_map(cur_pos);

if (offset < -0.005) {break;}

cur_pos += view_dir * offset * step_mult;
}

float cur_dist = sdf_map(cur_pos);

float alpha = 1.0 - clamp(cur_dist * -100.0, 0.0, 1.0);
ALPHA = pow(alpha, 2.0);

float vol_depth = distance(obj_position, cur_pos);

float col_mix_fac = pow(1.0 - exp(-col_distance_scale * vol_depth), 2.0);

vec3 vol_color = mix(col_near, col_far, col_mix_fac);

ALBEDO.xyz = vol_color * emission_boost;
}``````
###### Tags
Procedural, vfx
The shader code and all code snippets in this post are under CC0 license and can be used freely without the author's permission. Images and videos, and assets depicted in those, do not fall under this license. For more info, see our License terms.

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