~npisanti/scrapbook

scrapbook/sketches/infected_clocks/clock_2.frag -rw-r--r-- 9.2 KiB
7998d1d0Nicola Pisanti updates to latest API a day ago
                                                                                
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// ray marching code from 
// http://jamie-wong.com/2016/07/15/ray-marching-signed-distance-functions/
// https://www.shadertoy.com/view/Xtd3z7

// SDF shapes from 
// https://iquilezles.org/www/articles/distfunctions/distfunctions.htm

#ifdef GL_ES
precision mediump float;
#endif

#define PI 3.1415926535897932384626433832795
#define TWO_PI 6.2831853071795864769252867665590

uniform vec2 u_resolution;
uniform float u_time;
uniform sampler2D u_tex0;

// hash based 3d value noise
// function taken from https://www.shadertoy.com/view/XslGRr
// Created by inigo quilez - iq/2013
// License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

float vnhash( float n )
{
    return fract(sin(n)*43758.5453);
}

float vnoise( vec3 x )
{
    // The noise function returns a value in the range -1.0f -> 1.0f

    vec3 p = floor(x);
    vec3 f = fract(x);

    f       = f*f*(3.0-2.0*f);
    float n = p.x + p.y*57.0 + 113.0*p.z;

    return mix(mix(mix( vnhash(n+0.0), vnhash(n+1.0),f.x),
                   mix( vnhash(n+57.0), vnhash(n+58.0),f.x),f.y),
               mix(mix( vnhash(n+113.0), vnhash(n+114.0),f.x),
                   mix( vnhash(n+170.0), vnhash(n+171.0),f.x),f.y),f.z);
}


//
// Description : GLSL 2D simplex noise function
//      Author : Ian McEwan, Ashima Arts
//  Maintainer : ijm
//     Lastmod : 20110822 (ijm)
//     License :
//  Copyright (C) 2011 Ashima Arts. All rights reserved.
//  Distributed under the MIT License. See LICENSE file.
//  https://github.com/ashima/webgl-noise
//

// Some useful functions
vec3 mod289(vec3 x) { return x - floor(x * (1.0 / 289.0)) * 289.0; }
vec2 mod289(vec2 x) { return x - floor(x * (1.0 / 289.0)) * 289.0; }
vec3 permute(vec3 x) { return mod289(((x*34.0)+1.0)*x); }

float noise(vec2 v) {

    // Precompute values for skewed triangular grid
    const vec4 C = vec4(0.211324865405187,
                        // (3.0-sqrt(3.0))/6.0
                        0.366025403784439,
                        // 0.5*(sqrt(3.0)-1.0)
                        -0.577350269189626,
                        // -1.0 + 2.0 * C.x
                        0.024390243902439);
                        // 1.0 / 41.0

    // First corner (x0)
    vec2 i  = floor(v + dot(v, C.yy));
    vec2 x0 = v - i + dot(i, C.xx);

    // Other two corners (x1, x2)
    vec2 i1 = vec2(0.0);
    i1 = (x0.x > x0.y)? vec2(1.0, 0.0):vec2(0.0, 1.0);
    vec2 x1 = x0.xy + C.xx - i1;
    vec2 x2 = x0.xy + C.zz;

    // Do some permutations to avoid
    // truncation effects in permutation
    i = mod289(i);
    vec3 p = permute(
            permute( i.y + vec3(0.0, i1.y, 1.0))
                + i.x + vec3(0.0, i1.x, 1.0 ));

    vec3 m = max(0.5 - vec3(
                        dot(x0,x0),
                        dot(x1,x1),
                        dot(x2,x2)
                        ), 0.0);

    m = m*m ;
    m = m*m ;

    // Gradients:
    //  41 pts uniformly over a line, mapped onto a diamond
    //  The ring size 17*17 = 289 is close to a multiple
    //      of 41 (41*7 = 287)

    vec3 x = 2.0 * fract(p * C.www) - 1.0;
    vec3 h = abs(x) - 0.5;
    vec3 ox = floor(x + 0.5);
    vec3 a0 = x - ox;

    // Normalise gradients implicitly by scaling m
    // Approximation of: m *= inversesqrt(a0*a0 + h*h);
    m *= 1.79284291400159 - 0.85373472095314 * (a0*a0+h*h);

    // Compute final noise value at P
    vec3 g = vec3(0.0);
    g.x  = a0.x  * x0.x  + h.x  * x0.y;
    g.yz = a0.yz * vec2(x1.x,x2.x) + h.yz * vec2(x1.y,x2.y);
    return 130.0 * dot(m, g);
}


// code ported from alex-charlton.com/posts/Dithering_on_the_GPU/
// adapted for running on GLSL ES 2 ----
const mat4 dither_matrix = mat4( 
		vec4( 0,  8, 2, 10), 
		vec4( 12, 4, 14, 6), 
		vec4( 3, 11,  1, 9), 
		vec4( 15, 7, 13, 5)
);
float dither_4x4( float x, vec2 coord ){
	int ix = int(mod(coord.x, 4.0));
    int iy = int(mod(coord.y, 4.0));
    float d = dither_matrix[iy][ix] / 16.0;
    
    float closest = step( x, 0.5 );
    float distance = abs(closest - x);
	float branch = step( distance, d );

    return 2.0*branch*closest + 1.0 - closest - branch;
}
// -------------------------------------


// -------------- RAYMARCHING BOILERPLATE ---------------------------------------

const int MAX_MARCHING_STEPS = 255;
const float MIN_DIST = 0.0;
const float MAX_DIST = 100.0;
const float EPSILON = 0.0001;

float sphereSDF(vec3 p) {
    return length(p) - 1.0;
}

float sceneSDF(vec3 samplePoint);

float shortestDistanceToSurface(vec3 eye, vec3 marchingDirection, float start, float end) {
    float depth = start;
    for (int i = 0; i < MAX_MARCHING_STEPS; i++) {
        float dist = sceneSDF(eye + depth * marchingDirection);
        if (dist < EPSILON) {
			return depth;
        }
        depth += dist;
        if (depth >= end) {
            return end;
        }
    }
    return end;
}
            
vec3 rayDirection(float fieldOfView, vec2 size, vec2 fragCoord) {
    vec2 xy = fragCoord - size / 2.0;
    float z = size.y / tan(radians(fieldOfView) / 2.0);
    return normalize(vec3(xy, -z));
}

vec3 estimateNormal(vec3 p) {
    return normalize(vec3(
        sceneSDF(vec3(p.x + EPSILON, p.y, p.z)) - sceneSDF(vec3(p.x - EPSILON, p.y, p.z)),
        sceneSDF(vec3(p.x, p.y + EPSILON, p.z)) - sceneSDF(vec3(p.x, p.y - EPSILON, p.z)),
        sceneSDF(vec3(p.x, p.y, p.z  + EPSILON)) - sceneSDF(vec3(p.x, p.y, p.z - EPSILON))
    ));
}


float phongContribForLight(float k_d, vec3 p, vec3 eye, vec3 lightPos) {
    vec3 N = estimateNormal(p);
    vec3 L = normalize(lightPos - p);
    vec3 V = normalize(eye - p);
    vec3 R = normalize(reflect(-L, N));
    
    float dotLN = dot(L, N);
    float dotRV = dot(R, V);

    // Light not visible from this point on the surface
    if (dotLN < 0.0) { 
        return 0.0;
    } 
    // Light reflection in opposite direction as viewer, 
    // apply only diffuse  component
    if (dotRV < 0.0) { 
        return (k_d * dotLN);
    }
    return (k_d * dotLN );
}

mat4 viewMatrix(vec3 eye, vec3 center, vec3 up) {
    // Based on gluLookAt man page
    vec3 f = normalize(center - eye);
    vec3 s = normalize(cross(f, up));
    vec3 u = cross(s, f);
    return mat4(
        vec4(s, 0.0),
        vec4(u, 0.0),
        vec4(-f, 0.0),
        vec4(0.0, 0.0, 0.0, 1)
    );
}

// ------------------- FUNCTIONS -------------------------------
float lfo_ramp(  in float speed ){ return fract(u_time*speed); }
float lfo_tri(  in float speed ){ return abs( (fract(u_time*speed) * 2.0) - 1.0 ); }
float lfo_sin(  in float speed ){ return (sin(u_time*speed*TWO_PI)*0.5 + 0.5); }
// ------------------- 3D SDFs ---------------------------------

float sdBox( vec3 p, vec3 b ){
  vec3 q = abs(p) - b;
  return length(max(q,0.0)) + min(max(q.x,max(q.y,q.z)),0.0);
}

float sdEllipsoid( vec3 p, vec3 r ){
	float k0 = length(p/r);
	float k1 = length(p/(r*r));
	return k0*(k0-1.0)/k1;
}

mat4 rotateY(float theta) {
    float c = cos(theta);
    float s = sin(theta);

    return mat4(
        vec4(c, 0.0, s, 0.0),
        vec4(0.0, 1.0, 0.0, 0.0),
        vec4(-s, 0.0, c, 0.0),
        vec4(0.0, 0.0, 0.0, 1.0)
    );
}

// ------------------- SHADER ----------------------------------

void main(){
	// ------ raymarching parameters ------
	float distance = 70.0;
    float K_a = 0.05; // ambient gradient
    float K_d = 0.9; // light gradient
    vec3 light_pos = vec3(2.0, 4.0, 4.0 );

	float clok = u_time * 0.2;
	float theta = lfo_ramp( 0.03 ) * TWO_PI;
    vec3 camera = vec3( 7.0, 3.0, 0.0);
   
    vec3 look_at = vec3( 0, 0, 0 );

	// ------ more raymarching boilerplate ------
    vec2 st = gl_FragCoord.xy/u_resolution;
	vec3 viewDir = rayDirection(distance, u_resolution.xy, gl_FragCoord.xy);  
    mat4 viewToWorld = viewMatrix(camera, look_at, vec3(0.0, 1.0, 0.0));
    vec3 worldDir = (viewToWorld * vec4(viewDir, 0.0)).xyz;
    float dist = shortestDistanceToSurface(camera, worldDir, MIN_DIST, MAX_DIST);
    if (dist > MAX_DIST - EPSILON) {
        // Didn't hit anything
        gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0);
		return;
    }
    // The closest point on the surface to the eyepoint along the view ray
    vec3 p = camera + dist * worldDir;
      
    float c = K_a;
    c += phongContribForLight(K_d, p, camera, light_pos );

	gl_FragColor = vec4(vec3(c), 1.0);

	// dithering 
	c *= 1.4;
	float a = dither_4x4( c, gl_FragCoord.xy );
	gl_FragColor = vec4(vec3(a), 1.0);
}

#define FPS 8.0 
// 8 sec for a complete rotation

float sceneSDF(vec3 samplePoint) {
	float theta_step = TWO_PI / 64.0;

	float sdf = 0.0f;
	
	float stepping = floor(-u_time*FPS) * theta_step;
	vec4 rotated = rotateY(stepping) * vec4(samplePoint.xyz, 1.0);
	float o0 = sdBox( rotated.xyz, vec3( 0.05, 1.8, 0.5) ); 

	float displace = abs( fract( u_time*0.125 + 0.5 )*2.0 -1.0) * 0.25;

	
	float oadd = o0 + noise( vec2(rotated.z*2.0, rotated.y*3.5 + stepping ) ) * displace;
	sdf = min( o0, oadd );
	
	float offset = 1.8;

	stepping = floor(8.0 + u_time*FPS) * theta_step;

	for ( int i=0; i<8; ++i ){
		float r = stepping + float(i) * TWO_PI*0.125;
		float r2 = stepping + float(i) * TWO_PI*0.5;
		rotated = rotateY( r )  * vec4(samplePoint.xyz, 1.0);

		vec3 p0 = rotated.xyz + vec3(0.0, 0.0, offset);
		rotated.y += sin( r*2.0 + r2 ) * 0.2;
		float b = sdEllipsoid( rotated.xyz + vec3(0.0, 0.0, -offset), vec3(0.2, 0.08, 0.08 ) );
		sdf = min( b, sdf );
	}
	
	return sdf;    
}