This folder contains samples of the intermediate outputs in creating particle dispersion animations.

PARTICLE.DAT is the raw output from running HYSPLIT for a one hour emission that is modelled over a 19 hour duration. The particles are emitted from 30.251140,-93.278930 over a height of 0-25m.

plume_sulphur_202411270600_202411280600.bin.gz is the current format of the resulting binary file which we use to visualize the particles. While it is too large for a public website, we are exploring several options for a more succinct format. The file combines the 1 hour emission files for 5 sources over 24 total hours of emission. The binary is made up of 32 bit float least significant byte first in the following format:

x0, y0, z0, epoch0, x1, y1, z1, epoch1, packedColor
x and y are in web mercator space 0,0 is NW 255,255 is SE

The shaders to visualize the binary file are below. The shaders fade particles once they travel above breathing height:

WebGLVectorTile2Shaders.particleAltFadeVertexShader = `
attribute vec4 a_coord_0;
attribute float a_elev_0;
attribute float a_epoch_0;
attribute vec4 a_coord_1;
attribute float a_elev_1;
attribute float a_epoch_1;
attribute float a_color;
uniform mat4 u_map_matrix;
uniform float u_epoch;
uniform float u_size;
uniform float u_max_elev;
varying vec4 v_color;
vec4 unpackColor(float f) {
    vec4 color;
    color.b = floor(f / 256.0 / 256.0);
    color.g = floor((f - color.b * 256.0 * 256.0) / 256.0);
    color.r = floor(f - color.b * 256.0 * 256.0 - color.g * 256.0);
    color.a = 255.;
    return color / 256.0;
}
void main() {
    vec4 position;
    v_color = unpackColor(a_color);
    if (a_epoch_0 >= u_epoch || a_epoch_1 < u_epoch) {
        position = vec4(-1.,-1.,-1.,-1.);
    } else {
        float t = (u_epoch - a_epoch_0)/(a_epoch_1 - a_epoch_0);
        float min_elev = u_max_elev * 0.4;
        float current_elev = (a_elev_1 - a_elev_0) * t + a_elev_0;
        position = u_map_matrix * ((a_coord_1 - a_coord_0) * t + a_coord_0);
        v_color.a = min(max((u_max_elev-current_elev)/(u_max_elev-min_elev), 0.), 1.);
    }
    gl_Position = position;
    gl_PointSize = u_size;
}
`;

WebGLVectorTile2Shaders.particleAltFadeFragmentShader = `
/*precision mediump float;*/
varying vec4 v_color;
void main() {
  gl_FragColor = v_color;
}
`;