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// See http://www.iquilezles.org/articles/menger/menger.htm for the
// full explanation of how this was done
typedef float2 vec2;
typedef float3 vec3;
typedef float4 vec4;
#define sin native_sin
#define cos native_cos
#define tan native_tan
#define normalize fast_normalize
#define length fast_length
#define mod fmod
#define time 1.f
// fmod is not like glsl mod!
__attribute__((always_inline, overloadable))
float glsl_mod(float x,float y) { return x-y*floor(x/y); }
__attribute__((always_inline, overloadable))
float2 glsl_mod(float2 a,float2 b) { return (float2)(glsl_mod(a.x,b.x), glsl_mod(a.y,b.y)); }
__attribute__((always_inline, overloadable))
float3 glsl_mod(float3 a,float3 b) { return (float3)(glsl_mod(a.x,b.x), glsl_mod(a.y,b.y), glsl_mod(a.z,b.z)); }
inline vec3 reflect(vec3 I, vec3 N) {
return I - 2.0f * dot(N, I) * N;
}
inline uint pack_fp4(float4 u4) {
uint u;
u = (((uint) u4.x)) |
(((uint) u4.y) << 8) |
(((uint) u4.z) << 16);
return u;
}
#define OUTPUT do {\
const vec4 final = 255.f * max(min(gl_FragColor, (vec4)(1.f)), (vec4)(0.f)); \
dst[get_global_id(0) + get_global_id(1) * w] = pack_fp4(final); \
} while (0)
__attribute__((always_inline))
float maxcomp(vec3 p) { return max(p.x,max(p.y,p.z));}
__attribute__((always_inline))
float sdBox(vec3 p, vec3 b)
{
vec3 di = fabs(p) - b;
float mc = maxcomp(di);
return min(mc,length(max(di,0.0f)));
}
__attribute__((always_inline))
vec4 map(vec3 p)
{
float d = sdBox(p,(vec3)(1.0f));
float4 res = (vec4)(d,1.f,0.f,0.f);
float s = 1.0f;
for( int m=0; m<3; m++ )
{
vec3 a = glsl_mod(p*s, 2.0f)-1.0f;
s *= 3.0f;
float rx = fabs(1.0f - 3.0f*fabs(a.x));
float ry = fabs(1.0f - 3.0f*fabs(a.y));
float rz = fabs(1.0f - 3.0f*fabs(a.z));
float da = max(rx,ry);
float db = max(ry,rz);
float dc = max(rz,rx);
float c = (min(da,min(db,dc))-1.0f)/s;
if (c > d)
{
d = c;
res = (vec4)(d, 0.2f*da*db*dc, (1.0f+(float)(m))/4.0f, 0.0f);
}
}
return (vec4)(res.x,res.y,res.z,0.f);
}
// GLSL ES doesn't seem to like loops with conditional break/return...
#if 1
__attribute__((always_inline))
vec4 intersect( vec3 ro, vec3 rd )
{
float t = 0.0f;
for(int i=0;i<64;i++)
{
vec4 h = map(ro + rd*t);
if( h.x<0.002f )
return (vec4)(t,h.yzw);
t += h.x;
}
return (vec4)(-1.0f);
}
#else
__attribute__((always_inline))
vec4 intersect( vec3 ro, vec3 rd )
{
float t = 0.0f;
vec4 res = (vec4)(-1.0f);
for(int i=0;i<64;i++)
{
vec4 h = map(ro + rd*t);
if (h.x<0.002f)
{
if(res.x<0.0f) res = (vec4)(t,h.yzw);
}
t += h.x;
}
return res;
}
#endif
__attribute__((always_inline))
vec3 calcNormal(vec3 pos)
{
vec3 epsxyy = (vec3)(.001f,0.0f,0.0f);
vec3 epsyxy = (vec3)(0.0f,.001f,0.0f);
vec3 epsyyx = (vec3)(0.0f,0.0f,.001f);
vec3 nor;
nor.x = map(pos+epsxyy).x - map(pos-epsxyy).x;
nor.y = map(pos+epsyxy).x - map(pos-epsyxy).x;
nor.z = map(pos+epsyyx).x - map(pos-epsyyx).x;
return normalize(nor);
}
__kernel void compiler_menger_sponge(__global uint *dst, float resx, float resy, int w)
{
vec2 gl_FragCoord = (vec2)(get_global_id(0), get_global_id(1));
vec2 p=-1.0f+2.0f*gl_FragCoord.xy/(vec2)(resx,resy);
// light
vec3 light = normalize((vec3)(1.0f,0.8f,-0.6f));
float ctime = time;
// camera
vec3 ro = 1.1f*(vec3)(2.5f*cos(0.5f*ctime),1.5f*cos(ctime*.23f),2.5f*sin(0.5f*ctime));
vec3 ww = normalize((vec3)(0.0f) - ro);
vec3 uu = normalize(cross( (vec3)(0.0f,1.0f,0.0f), ww ));
vec3 vv = normalize(cross(ww,uu));
vec3 rd = normalize( p.x*uu + p.y*vv + 1.5f*ww );
vec3 col = (vec3)(0.0f);
vec4 tmat = intersect(ro,rd);
#if 0
if( tmat.x>0.0 )
col = (vec3)(
0.6f+0.4f*cos(5.0f+6.2831f*tmat.z),
0.6f+0.4f*cos(5.4f+6.2831f*tmat.z),
0.6f+0.4f*cos(5.7f+6.2831f*tmat.z) );
#else
if( tmat.x>0.0f )
{
vec3 pos = ro + tmat.x*rd;
vec3 nor = calcNormal(pos);
float dif1 = max(0.4f + 0.6f*dot(nor,light),0.0f);
float dif2 = max(0.4f + 0.6f*dot(nor,(vec3)(-light.x,light.y,-light.z)),0.0f);
// shadow
float ldis = 4.0f;
vec4 shadow = intersect( pos + light*ldis, -light );
if( shadow.x>0.0f && shadow.x<(ldis-0.01f) ) dif1=0.0f;
float ao = tmat.y;
col = 1.0f*ao*(vec3) (0.2f,0.2f,0.2f);
col += 2.0f*(0.5f+0.5f*ao)*dif1*(vec3)(1.0f,0.97f,0.85f);
col += 0.2f*(0.5f+0.5f*ao)*dif2*(vec3)(1.0f,0.97f,0.85f);
col += 1.0f*(0.5f+0.5f*ao)*(0.5f+0.5f*nor.y)*(vec3)(0.1f,0.15f,0.2f);
// gamma lighting
col = col*0.5f+0.5f*sqrt(col)*1.2f;
vec3 matcol = (vec3)(
0.6f+0.4f*cos(5.0f+6.2831f*tmat.z),
0.6f+0.4f*cos(5.4f+6.2831f*tmat.z),
0.6f+0.4f*cos(5.7f+6.2831f*tmat.z) );
col *= matcol;
col *= 1.5f*exp(-0.5f*tmat.x);
}
#endif
vec4 gl_FragColor = (vec4)(col,1.0f);
OUTPUT;
}
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