flame.glsl

#version 420 core

uniform float fGlobalTime; // in seconds
uniform vec2 v2Resolution; // viewport resolution (in pixels)
uniform float fFrameTime; // duration of the last frame, in seconds

uniform sampler1D texFFT; // towards 0.0 is bass / lower freq, towards 1.0 is higher / treble freq
uniform sampler1D texFFTSmoothed; // this one has longer falloff and less harsh transients
uniform sampler1D texFFTIntegrated; // this is continually increasing
uniform sampler2D texPreviousFrame; // screenshot of the previous frame
uniform sampler2D texChecker;
uniform sampler2D texNoise;
uniform sampler2D texTex1;
uniform sampler2D texTex2;
uniform sampler2D texTex3;
uniform sampler2D texTex4;

layout(r32ui) uniform coherent restrict uimage2D[3] computeTex;
layout(r32ui) uniform coherent restrict uimage2D[3] computeTexBack;

layout(location = 0) out vec4 out_color; // out_color must be written in order to see anything


#define U gl_FragCoord.xy
#define R vec2(v2Resolution.xy)
#define T fGlobalTime 

#define pi acos(-1.)
#define tau (acos(-1.)*2.)


#define rot(a) mat2(cos(a),-sin(a),sin(a),cos(a))



// hashes
uint seed = 12512;
uint hashi( uint x){
    x ^= x >> 16;x *= 0x7feb352dU;x ^= x >> 15;x *= 0x846ca68bU;x ^= x >> 16;
    return x;
}

#define hash_f_s(s)  ( float( hashi(uint(s)) ) / float( 0xffffffffU ) )
#define hash_f()  ( float( seed = hashi(seed) ) / float( 0xffffffffU ) )
#define hash_v2()  vec2(hash_f(),hash_f())
#define hash_v3()  vec3(hash_f(),hash_f(),hash_f())
#define hash_v4()  vec3(hash_f(),hash_f(),hash_f(),hash_f())

vec2 sample_disk(){
    vec2 r = hash_v2();
    return vec2(sin(r.x*tau),cos(r.x*tau))*sqrt(r.y);
}

// point projection
ivec2 proj_p(vec3 p, float t){
  // arbitrary camera stuff
  float tt = t*2;
  p += sin(vec3(1.1,0.78,0.6)*tt*0.3)*0.1;
  p += sin(vec3(1.1,0.78,0.6)*tt*1.)*0.1;
  p.xz *= rot(tt*0.25 + sin(tt*0.25));
  p.xy *= rot(sin(tt*0.3)*0.2);
  p.z -= -5.5;
  
  // perspective proj
  p.xy /= p.z*0.5;
  
  // depth of field
  p.xy += sample_disk() * abs(p.z - 5. + sin(T))*0.01;
  
  // convert point to ivec2. From 0 to resolution.xy
  ivec2 q = ivec2((p.xy + vec2(R.x/R.y,1)*0.5)*vec2(R.y/R.x,1)*R);
  if(any(greaterThan(q, ivec2(R))) || any(lessThan(q, ivec2(0)))){
      q = ivec2(-1);
  }
  return q;
}


void store_pixel(ivec2 px_coord, vec3 col){
  // colour quantized to integer.
  ivec3 quant_col = ivec3(col * 1000);
  // no clue why it wants ivec4() here...
  imageStore(computeTex[0], px_coord, ivec4(quant_col.x)); 
  imageStore(computeTex[1], px_coord, ivec4(quant_col.y)); 
  imageStore(computeTex[2], px_coord, ivec4(quant_col.z)); 
}

void add_to_pixel(ivec2 px_coord, vec3 col){
  // colour quantized to integer.
  ivec3 quant_col = ivec3(col * 1000);
  imageAtomicAdd(computeTex[0], px_coord, quant_col.x);
  imageAtomicAdd(computeTex[1], px_coord, quant_col.y);
  imageAtomicAdd(computeTex[2], px_coord, quant_col.z);
}

vec3 read_pixel(ivec2 px_coord){
  return 0.001*vec3(
    imageLoad(computeTexBack[0],px_coord).x,
    imageLoad(computeTexBack[1],px_coord).x,
    imageLoad(computeTexBack[2],px_coord).x
  );
}


void main(void){
	vec2 uv = vec2(gl_FragCoord.x / v2Resolution.x, gl_FragCoord.y / v2Resolution.y);
	uv -= 0.5;
	uv /= vec2(v2Resolution.y / v2Resolution.x, 1);
  
  // Init hash
	seed = 215125125;
  seed += hashi(uint(U.x)) + hashi(uint(U.y)*125);
	
  
  vec3 col = vec3(0);
  
  
  // Only run for the first 400 horizontal pixels
  if(gl_FragCoord.x < 400){
    int iters = 30;
    
    float t = T - hash_f()*1./30;

    float env = t + sin(t)*0.5;
    float envb = sin(t*0.45);

    vec3 p = hash_v3();
    
    vec3 acc = vec3(1);
    
    for(int i = 0; i < iters; i++){
        float r = hash_f();
        
        // basic Chaos Game stuff. Pick randomly from a couple of transforms, can be anything.
        // Computerphile video or my article explains it.
        
        vec3 dest = vec3(1);
        if(r<.25){
            dest = vec3(-1,-1,-0.5 );
        } else if(r<.0){
            dest = vec3(-1,1,-0.5 + cos(T));
        } else if (r < 0.75){
            dest = vec3(1,-1,-0.5);
        } else {
            dest = vec3(0,0,2.);
        }
        if(hash_f() < 0.5){
          dest = -dest;
        }
        if(hash_f() < 0.5){
          p = mix(p,dest,hash_f()*1.5);
        } else{
          p = mix(p,dest,0.5);
        }
        
        // some arbitrary colouring algorithm.
        acc += (1.0 + sin(T*0.2))/dot(p,p);
        
        ivec2 q = proj_p(p,t);
        
        // if inside screen
        if(q.x >= 0){
          add_to_pixel(
            q, 0.5 + 0.5 * sin(vec3(3,2,1)*acc*0.6)
          );
        }
    }
  }
  
  
  
  vec3 s = read_pixel(ivec2(gl_FragCoord.xy))*0.1;
  
  // tonemap stuff
  s = s/(1+s*1.);
  s = mix(s,smoothstep(0.,1.,s),0.);
  s *= 1.2;
  col = vec3(1)*1.0;
  col -= s;
  col = pow(col,vec3(.45454));
  
  
	out_color = vec4(col,0);
}