Error(s) in re-building vignettes:
--- re-building 'models-from-other.Rmd' using rmarkdown
trying URL 'http://ryantimpe.com/files/mf_unicorn.PNG'
Content type 'image/png' length 277758 bytes (271 KB)
==================================================
downloaded 271 KB

Warning in snapshot3d(paste0(name, ".png")) :
  webshot = TRUE requires the webshot2 package; using rgl.snapshot() instead
Quitting from lines 44-53 (models-from-other.Rmd) 
Error: processing vignette 'models-from-other.Rmd' failed with diagnostics:
pixmap save format not supported in this build
--- failed re-building 'models-from-other.Rmd'

--- re-building 'models-from-program.Rmd' using rmarkdown
Warning in snapshot3d(paste0(name, ".png")) :
  webshot = TRUE requires the webshot2 package; using rgl.snapshot() instead
Quitting from lines 33-48 (models-from-program.Rmd) 
Error: processing vignette 'models-from-program.Rmd' failed with diagnostics:
pixmap save format not supported in this build
--- failed re-building 'models-from-program.Rmd'

--- re-building 'models-from-tables.Rmd' using rmarkdown
Warning in snapshot3d(paste0(name, ".png")) :
  webshot = TRUE requires the webshot2 package; using rgl.snapshot() instead
Quitting from lines 37-49 (models-from-tables.Rmd) 
Error: processing vignette 'models-from-tables.Rmd' failed with diagnostics:
pixmap save format not supported in this build
--- failed re-building 'models-from-tables.Rmd'

--- re-building 'models-piece-type.Rmd' using rmarkdown
Warning in snapshot3d(paste0(name, ".png")) :
  webshot = TRUE requires the webshot2 package; using rgl.snapshot() instead
Quitting from lines 50-61 (models-piece-type.Rmd) 
Error: processing vignette 'models-piece-type.Rmd' failed with diagnostics:
pixmap save format not supported in this build
--- failed re-building 'models-piece-type.Rmd'

--- re-building 'mosaics.Rmd' using rmarkdown
trying URL 'http://ryantimpe.com/files/mf_unicorn.PNG'
Content type 'image/png' length 277758 bytes (271 KB)
==================================================
downloaded 271 KB

Warning in snapshot3d(paste0(name, ".png")) :
  webshot = TRUE requires the webshot2 package; using rgl.snapshot() instead
Quitting from lines 133-143 (mosaics.Rmd) 
Error: processing vignette 'mosaics.Rmd' failed with diagnostics:
pixmap save format not supported in this build
--- failed re-building 'mosaics.Rmd'

SUMMARY: processing the following files failed:
  'models-from-other.Rmd' 'models-from-program.Rmd'
  'models-from-tables.Rmd' 'models-piece-type.Rmd' 'mosaics.Rmd'

Error: Vignette re-building failed.
Execution halted