precision highp float; uniform float time; uniform vec2 mouse; uniform vec2 resolution; #define TWO_PI 6.28318530718 const float GRAVITY = -9.8 * 2.5; #define MAX_DISTANCE 1e8 const vec3 LIGHT_UP = normalize(vec3(0.1, 1.0, 0.2)); #define PATHWAY_WIDTH 3.0 #define SPHERE_RADIUS 2.0 #define SPHERE_NUM 16.0 #define HORIZONTAL_SPEED 8.0 #define NON_FALL_TIME 15.0 #define FALL_TIME 3.0 const float SIM_TIME = NON_FALL_TIME + FALL_TIME; struct Surface { float t; vec3 pos; vec3 nor; vec3 diffColor; vec3 specColor; float diff; float spec; }; mat2 rotate(float r) { float c = cos(r); float s = sin(r); return mat2(c, s, -s, c); } float getFreeFallPosition(float t, float v0) { return 0.5 * GRAVITY * t * t + v0 * t + 0.0; } float distSpheres(vec3 p, float r) { float d = MAX_DISTANCE; for (float i = 0.0; i < SPHERE_NUM; i += 1.0) { float tm = mod(time + i * SIM_TIME / SPHERE_NUM, SIM_TIME); vec3 offset = vec3( HORIZONTAL_SPEED * (tm - NON_FALL_TIME), (tm < NON_FALL_TIME ? 0.0 : getFreeFallPosition(tm - NON_FALL_TIME, 0.0)) + r, 0.0 ); d = min(d, length(p - offset) - r); } return d; } float distPathway(vec3 p, float width) { p.z = abs(p.z) - 0.5 * width; float d1 = length(max(p, 0.0)) + min(max(p.x, max(p.y, p.z)), 0.0); return d1; } float map(vec3 p) { float ds = distSpheres(p, SPHERE_RADIUS); float dp = distPathway(p, PATHWAY_WIDTH); return min(ds, dp); } float ambientOcclusion(vec3 p, vec3 n, float step) { float ao = 1.0; float amp = 0.5; for (float i = 1.0; i <= 5.0; i += 1.0) { float t = i * step; float d = max(0.0, map(p + t * n)); ao -= amp * (t - d) / t; amp *= 0.5; } return ao; } bool hitSphere(vec3 ro, vec3 rd, float r, vec3 offset, inout Surface surf) { ro -= offset; float a = dot(rd, rd); float b = 2.0 * dot(ro, rd); float c = dot(ro, ro) - r * r; float d = b * b - 4.0 * a * c; if (d < 0.0) { return false; } float sqrtD = sqrt(d); float t = (-b - sqrtD) / (2.0 * a); if (t > 0.0 && t < surf.t) { surf.t = t; surf.pos = ro + offset + t * rd; surf.nor = normalize(ro + t * rd); return true; } return false; } void hitSpheres(vec3 ro, vec3 rd, float r, inout Surface surf) { for (float i = 0.0; i < SPHERE_NUM; i += 1.0) { float tm = mod(time + i * SIM_TIME / SPHERE_NUM, SIM_TIME); vec3 offset = vec3( HORIZONTAL_SPEED * (tm - NON_FALL_TIME), (tm < NON_FALL_TIME ? 0.0 : getFreeFallPosition(tm - NON_FALL_TIME, 0.0)) + r, 0.0 ); if (hitSphere(ro, rd, SPHERE_RADIUS, offset, surf)) { vec3 objectPos = surf.pos - offset; objectPos.xy *= rotate(-2.0 * TWO_PI * SPHERE_RADIUS / HORIZONTAL_SPEED * time); if (sin(objectPos.y * 5.0) > 0.0) { surf.diffColor = vec3(0.8); surf.specColor = vec3(0.04); surf.diff = 1.0; surf.spec = 0.5; } else { surf.diffColor = vec3(0.1); surf.specColor = vec3(0.08); surf.diff = 0.5; surf.spec = 0.5; } } } } void hitPathway(vec3 ro, vec3 rd, float width, inout Surface surf) { float hw = 0.5 * width; bool hit = false; float ty = -ro.y / rd.y; if (ty > 0.0 && ty < surf.t) { vec3 p = ro + ty * rd; if (p.x < 0.0 && p.z < hw && p.z > -hw) { hit = true; surf.t = ty; surf.pos = p; surf.nor = vec3(0.0, 1.0, 0.0); } } float tx = -ro.x / rd.x; if (tx > 0.0 && tx < surf.t) { vec3 p = ro + tx * rd; if (p.y < 0.0 && p.z < hw && p.z > -hw) { hit = true; surf.t = tx; surf.pos = p; surf.nor = vec3(1.0, 0.0, 0.0); } } float tpz = (hw - ro.z) / rd.z; if (tpz > 0.0 && tpz < surf.t) { vec3 p = ro + tpz * rd; if (p.x < 0.0 && p.y < 0.0) { hit = true; surf.t = tpz; surf.pos = p; surf.nor = vec3(0.0, 0.0, 1.0); } } float tmz = (-hw - ro.z) / rd.z; if (tmz > 0.0 && tmz < surf.t) { vec3 p = ro + tmz * rd; if (p.x < 0.0 && p.y < 0.0) { hit = true; surf.t = tmz; surf.pos = p; surf.nor = vec3(0.0, 0.0, -1.0); } } if (hit) { surf.diffColor = vec3(0.8); surf.specColor = vec3(0.2); surf.diff = 1.0; surf.spec = 0.5; } } bool hitObjects(vec3 ro, vec3 rd, inout Surface surf) { surf.t = MAX_DISTANCE; hitSpheres(ro, rd, SPHERE_RADIUS, surf); hitPathway(ro, rd, PATHWAY_WIDTH, surf); return surf.t != MAX_DISTANCE; } vec3 background(vec3 rd) { return mix(vec3(0.0), vec3(0.05, 0.65, 0.8), rd.y * 0.5 + 0.5); } vec3 fresnelSchlick(vec3 f0, float cosine) { return f0 + (1.0 - f0) * pow(1.0 - cosine, 5.0); } vec3 getColor(vec3 ro, vec3 rd) { vec3 color = vec3(0.0); vec3 scale = vec3(1.0); Surface surf; for (int i = 0; i < 3; i++) { if (!hitObjects(ro, rd, surf)) { color += scale * background(rd); break; } else { vec3 diff = surf.diff * surf.diffColor * (dot(surf.nor, LIGHT_UP) * 0.5 + 0.5); float ao = ambientOcclusion(surf.pos, surf.nor, 0.1); color += scale * ao * diff; } if (surf.spec == 0.0) { break; } vec3 refDir = reflect(rd, surf.nor); float dotNR = clamp(dot(surf.nor, refDir), 0.0, 1.0); vec3 fresnel = fresnelSchlick(surf.specColor, dotNR); scale *= surf.spec * fresnel; ro = surf.pos + 0.01 * refDir; rd = refDir; } return color; } void main(void) { vec2 st = (2.0 * gl_FragCoord.xy - resolution) / min(resolution.x, resolution.y); vec3 ro = vec3(10.0, 10.0, 20.0); vec3 ta = vec3(0.0); vec3 z = normalize(ta - ro); vec3 up = vec3(0.0, 1.0, 0.0); vec3 x = normalize(cross(z, up)); vec3 y = normalize(cross(x, z)); vec3 rd = normalize(x * st.x + y * st.y + z * 2.0); vec3 c = getColor(ro, rd); gl_FragColor = vec4(pow(c, vec3(1.0 / 2.2)), 1.0); }

Physics #1