/**
 * drawProgram          drawVert drawFrag
 * screenProgram        screenVert screenFrag
 * updateProgram        updateVert updateFrag
 * fullScreenProgram    fullScreenVert fullScreenFrag
 */
export declare const drawVert = "\n precision mediump float;\n\n attribute float a_index;\n\n uniform sampler2D u_particles;\n uniform float u_particles_res;\n\n varying vec2 v_particle_pos;\n\n void main() {\n     vec4 color = texture2D(u_particles, vec2(\n         fract(a_index / u_particles_res),\n         floor(a_index / u_particles_res) / u_particles_res)\n     );\n\n     // decode current particle position from the pixel's RGBA value\n     v_particle_pos = vec2( color.r / 255.0 + color.b, color.g / 255.0 + color.a);\n\n     gl_PointSize = 1.0;\n     gl_Position = vec4(2.0 * v_particle_pos.x - 1.0, 1.0 - 2.0 * v_particle_pos.y, 0, 1);\n }";
export declare const drawFrag = "\n precision mediump float;\n\n uniform sampler2D u_wind;\n uniform vec2 u_wind_min;\n uniform vec2 u_wind_max;\n uniform sampler2D u_color_ramp;\n\n varying vec2 v_particle_pos;\n\n void main() {\n     vec2 velocity = mix(u_wind_min, u_wind_max, texture2D(u_wind, v_particle_pos).rg);\n     float speed_t = length(velocity) / length(u_wind_max);\n\n     // color ramp is encoded in a 16x16 texture\n     vec2 ramp_pos = vec2( fract(16.0 * speed_t), floor(16.0 * speed_t) / 16.0);\n\n     gl_FragColor = texture2D(u_color_ramp, ramp_pos);\n }";
export declare const updateVert = "\n precision mediump float;\n\n attribute vec2 a_pos;\n\n varying vec2 v_tex_pos;\n\n void main() {\n     v_tex_pos = a_pos;\n     gl_Position = vec4(1.0 - 2.0 * a_pos, 0, 1);\n     // framebuffer \u59CB\u7EC8\u7528\u94FA\u6EE1\u5C4F\u5E55\u7684 texture\n }";
export declare const updateFrag = "\n precision highp float;\n\n uniform sampler2D u_particles;\n uniform sampler2D u_wind;\n uniform vec2 u_wind_res;\n uniform vec2 u_wind_min;\n uniform vec2 u_wind_max;\n uniform float u_rand_seed;\n uniform float u_speed_factor;\n uniform float u_drop_rate;\n uniform float u_drop_rate_bump;\n\n varying vec2 v_tex_pos;\n\n // pseudo-random generator\n const vec3 rand_constants = vec3(12.9898, 78.233, 4375.85453);\n float rand(const vec2 co) {\n float t = dot(rand_constants.xy, co);\n     return fract(sin(t) * (rand_constants.z + t));\n }\n\n // wind speed lookup; use manual bilinear filtering based on 4 adjacent pixels for smooth interpolation\n vec2 lookup_wind(const vec2 uv) {\n     // return texture2D(u_wind, uv).rg; // lower-res hardware filtering\n     vec2 px = 1.0 / u_wind_res;\n     vec2 vc = (floor(uv * u_wind_res)) * px;\n     vec2 f = fract(uv * u_wind_res);\n     vec2 tl = texture2D(u_wind, vc).rg;\n     vec2 tr = texture2D(u_wind, vc + vec2(px.x, 0)).rg;\n     vec2 bl = texture2D(u_wind, vc + vec2(0, px.y)).rg;\n     vec2 br = texture2D(u_wind, vc + px).rg;\n     return mix(mix(tl, tr, f.x), mix(bl, br, f.x), f.y);\n }\n\n void main() {\n     vec4 color = texture2D(u_particles, v_tex_pos);\n     vec2 pos = vec2(\n         color.r / 255.0 + color.b,\n         color.g / 255.0 + color.a); // decode particle position from pixel RGBA\n     vec2 velocity = mix(u_wind_min, u_wind_max, lookup_wind(pos));\n     float speed_t = length(velocity) / length(u_wind_max);\n\n     // take EPSG:4236 distortion into account for calculating where the particle moved\n     float distortion = cos(radians(pos.y * 180.0 - 90.0));\n     vec2 offset = vec2(velocity.x / distortion, -velocity.y) * 0.0001 * u_speed_factor;\n\n     // update particle position, wrapping around the date line\n     pos = fract(1.0 + pos + offset);\n\n     // a random seed to use for the particle drop\n     vec2 seed = (pos + v_tex_pos) * u_rand_seed;\n\n     // drop rate is a chance a particle will restart at random position, to avoid degeneration\n     float drop_rate = u_drop_rate + speed_t * u_drop_rate_bump;\n     float drop = step(1.0 - drop_rate, rand(seed));\n\n     vec2 random_pos = vec2(\n         rand(seed + 1.3),\n         rand(seed + 2.1));\n         pos = mix(pos, random_pos, drop);\n\n     // encode the new particle position back into RGBA\n     gl_FragColor = vec4(\n         fract(pos * 255.0),\n         floor(pos * 255.0) / 255.0);\n }";
export declare const fullScreenVert = "\n     precision mediump float;\n\n     attribute vec2 a_pos;\n\n     varying vec2 v_tex_pos;\n\n     void main() {\n         v_tex_pos = a_pos;\n         gl_Position = vec4(1.0 - 2.0 * a_pos, 0.0, 1.0);\n         gl_PointSize = 100.0;\n }";
export declare const fullScreenFrag = "\n precision mediump float;\n\n uniform sampler2D u_screen;\n uniform float u_opacity;\n varying vec2 v_tex_pos;\n\n void main() {\n     vec4 color = texture2D(u_screen, 1.0 - v_tex_pos);\n\n     // a hack to guarantee opacity fade out even with a value close to 1.0\n     gl_FragColor = vec4(floor(255.0 * color * u_opacity) / 255.0);\n }";