1+ #pragma kernel CSMain
2+
3+ // textures
4+ RWTexture2D<float4> Texture;
5+ Texture2D<float4> Source;
6+
7+ // matrixes
8+ float4x4 CamToWorld;
9+ float4x4 CamInverseProjection;
10+
11+ // variables
12+ int Iterations;
13+ float Size;
14+ float3 Offset;
15+ float SizeDec;
16+
17+ // constants
18+ static const int steps = 100;
19+ static const float epsilon = 0.00001;
20+ /*static const float PI = 3.14159265f;
21+
22+ // rotate functions https://en.wikipedia.org/wiki/Rotation_matrix
23+ float DegToRad(float a) { return a * PI / 180; }
24+ float4x4 rotateX(float a) {
25+ a = DegToRad(a);
26+ float c = cos(a); float s = sin(a);
27+ return float4x4(float4(1, 0, 0, 0), float4(0, c, -s, 0), float4(0, s, c, 0), float4(0, 0, 0, 1));
28+ }
29+ float4x4 rotateY(float a) {
30+ a = DegToRad(a);
31+ float c = cos(a); float s = sin(a);
32+ return float4x4(float4(c, 0, s, 0), float4(0, 1, 0, 0), float4(-s, 0, c, 0), float4(0, 0, 0, 1));
33+ }
34+ float4x4 rotateZ(float a) {
35+ a = DegToRad(a);
36+ float c = cos(a); float s = sin(a);
37+ return float4x4(float4(c, -s, 0, 0), float4(s, c, 0, 0), float4(0, 0, 1, 0), float4(0, 0, 0, 1));
38+ }
39+ float3 transform(float3 p, float4x4 m) {
40+ return mul(m, float4(p, 1.0)).xyz;
41+ }
42+
43+ // box distance estimator from https://iquilezles.org/www/articles/distfunctions/distfunctions.htm
44+ float DEBox(float3 p, float s) {
45+ float3 q = abs(p) - float3(s, s, s);
46+ return length(max(q, 0.0)) + min(max(q.x, max(q.y, q.z)), 0.0);
47+ }
48+
49+ // 2D box distance estimator from https://iquilezles.org/www/articles/distfunctions2d/distfunctions2d.htm
50+ float DEBox2D(float2 p, float s) {
51+ float2 d = abs(p) - s;
52+ return length(max(d, 0.0)) + min(max(d.x, d.y), 0);
53+ }
54+
55+ // cross distance estimator from https://iquilezles.org/www/articles/distfunctions/distfunctions.htm
56+ float DECross(float3 p, float s) {
57+ s = s / 3;
58+ float d = DEBox2D(p.xy, s);
59+ d = min(d, DEBox2D(p.xz, s));
60+ return min(d, DEBox2D(p.yz, s));
61+ }
62+
63+ float DETest(float3 p, float s) {
64+ return max(DEBox(p, s), -DECross(p, s*3));
65+ }*/
66+
67+ // octahedron distance estimator from https://www.iquilezles.org/www/articles/distfunctions/distfunctions.htm
68+ float DEOctahedron(float3 p, float s) {
69+ p = abs(p);
70+ float m = p.x + p.y + p.z - s;
71+ float3 q;
72+ if (3.0 * p.x < m) q = p.xyz;
73+ else if (3.0 * p.y < m) q = p.yzx;
74+ else if (3.0 * p.z < m) q = p.zxy;
75+ else return m * 0.57735027;
76+
77+ float k = clamp(0.5 * (q.z - q.y + s), 0.0, s);
78+ return length(float3(q.x, q.y - s + k, q.z - k));
79+ }
80+
81+ // fold space from http://blog.hvidtfeldts.net/index.php/2011/08/distance-estimated-3d-fractals-iii-folding-space
82+ float3 Fold(float3 p, float3 n) {
83+ return p - 2.0 * min(0.0, dot(p, n)) * n;
84+ }
85+
86+ // distance to scene
87+ float DE(float3 p) {
88+ int i = 0;
89+ while (i < Iterations) {
90+ p *= SizeDec;
91+ p = Fold(p, normalize(float3(0, 1, 1)));
92+ p = Fold(p, normalize(float3(0, 1, -1)));
93+ p = Fold(p, normalize(float3(1, 1, 0)));
94+ p = Fold(p, normalize(float3(-1, 1, 0)));
95+ p -= Offset * Size;
96+ i++;
97+ }
98+ return DEOctahedron(p, Size) / pow(SizeDec, i);
99+ }
100+
101+ // ray
102+ struct Ray {
103+ float3 origin;
104+ float3 direction;
105+ };
106+
107+ // from http://blog.three-eyed-games.com/2018/05/03/gpu-ray-tracing-in-unity-part-1/
108+ Ray CreateRay(float3 origin, float3 direction) {
109+ Ray ray;
110+ ray.origin = origin;
111+ ray.direction = direction;
112+ return ray;
113+ }
114+
115+ // from http://blog.three-eyed-games.com/2018/05/03/gpu-ray-tracing-in-unity-part-1/
116+ Ray CreateCameraRay(float2 uv) {
117+ float3 origin = mul(CamToWorld, float4(0, 0, 0, 1)).xyz;
118+ float3 direction = mul(CamInverseProjection, float4(uv, 0, 1)).xyz;
119+ direction = mul(CamToWorld, float4(direction, 0)).xyz;
120+ direction = normalize(direction);
121+ return CreateRay(origin, direction);
122+ }
123+
124+ // cast a ray and return the result
125+ float March(Ray ray) {
126+ float d = 0;
127+ float3 eye = ray.origin;
128+
129+ int s = 0;
130+ while (s < steps) {
131+ d = DE(ray.origin); // calculate distance
132+ if (length(eye - ray.origin) > 200) s = steps; // to far away
133+ if (d < epsilon) break; // hit
134+ ray.origin += ray.direction * d; // march
135+ s++; // next iteration
136+ }
137+
138+ return 1 - float(s / float(steps));
139+ }
140+
141+ [numthreads(8,8,1)]
142+ void CSMain (uint3 id : SV_DispatchThreadID) {
143+
144+ // convert into range [-1, 1]
145+ float w, h; Texture.GetDimensions(w, h);
146+ float2 uv = id.xy / float2(w, h) * 2 - 1;
147+
148+ // create ray
149+ Ray ray = CreateCameraRay(uv);
150+
151+ float res = March(ray);
152+ //float4 ao = res * float4(0.1, 0.74, 0.61, 0);
153+ float4 ao = res * float4(0.6, 0.6, 0.6, 0);
154+ Texture[id.xy] = Source[id.xy] + ao;
155+ }
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