Rendering a light traveling through a spiral

spiral.R

library(rayrender)

drawspiral = function(n, x = 0, material=diffuse(color="white")) {
  segments = list()
  for(i in seq_len(n)) {
    if(i %% 2 != 0) {
      segments[[i]] = cylinder(z=0.5,x=x, length=0.5, radius=0.5*i, material = material, phi_min = 90, phi_max = 270)
    } else {
      segments[[i]] = cylinder(z=0,x=x, length=0.5, radius=0.5*i, material = material, phi_min = 90, phi_max = 270, angle=c(0,180,0))
    } 
  }
  return(do.call(rbind, segments))
}

spirallightz = function(t) {
  side = floor(t/30)
  (0.5+0.5*side) * 1 *sinpi(6*t/180)
}
spirallightx = function(t) {
  side = floor(t/30)
  ifelse(side %% 2 != 0, -(0.5+side*0.5) *1*cospi(6*t/180), 0.5 - (0.5+side*0.5) *1*cospi(6*t/180)  )
}

xposfunction = function(x0,v0,a0, loss=1/4, low,starttime,cutoff,length=60) {
  xpos = rep(x0,length)
  for(i in starttime:length) {
    x0 = x0 + v0
    if(x0 > low) {
      v0 = v0 - a0
    } else {
      v0 = -v0*loss
      x0 = x0 + v0
    }
    xpos[i] = x0
  }
  xpos[(cutoff+starttime):length] = low
  xpos
}

bouncy = xposfunction(10,0,0.1, low=0.3,loss=0.5,starttime=1,cutoff=52)

for(i in seq(1,390,by=1)) {
  if(i <= 330) {
    xz_rect(xwidth=100,zwidth=100,y = -0.25, material  = diffuse(checkercolor ="grey20", color="grey10",sigma = 90)) %>%
                  add_object(group_objects(sphere(x=spirallightz(i),y=0.3,z=-spirallightx(i),
                                                  radius=0.2,material=light(intensity = 700)), 
                                           group_translate = c(0,0,0.5))) %>%
                  add_object(drawspiral(12, material = diffuse(color="green",sigma=90))) %>%
                  render_scene(parallel=TRUE, rotate_env = 180, fov=20, 
                               lookfrom = c(0,20,30), filename = glue::glue("spiral{i}"))
  } else {
    xz_rect(xwidth=100,zwidth=100,y = -0.25, material  = diffuse(checkercolor ="grey20", color="grey10",sigma = 90)) %>%
      add_object(group_objects(sphere(x=spirallightz(1),y=bouncy[i-330],z=-spirallightx(1),radius=0.2,
                                      material=light(intensity = 700 * (10-bouncy[i-330])/9.7)), 
                               group_translate = c(0,0,0.5))) %>%
      add_object(group_objects(sphere(x=spirallightz(i),y=0.25-(i-330)/30,z=-spirallightx(i),
                                      radius=0.2,material=light(intensity = 700)), 
                               group_translate = c(0,0,0.5))) %>%
      add_object(drawspiral(12, material = diffuse(color="green",sigma=90))) %>%
      render_scene(parallel=TRUE, rotate_env = 180, fov=20, lookfrom = c(0,20,30), 
                   filename = glue::glue("spiral{i}"))
  }
}