Silvam does a great overview of how to insert the 3d crowds in part four of his series, which you can find here
:
https://youtu.be/t5pnZyirfYE?t=874
I wanted to post the 4 lines of code for each of the levels of popularity so you don't have to go looking in a .mtl file for them.
Level 1:
Ni 1.000000
d 1.000000
illum 1
map_Kd ../attendance/seating_popularity1.jpg
Level 2:
Ni 1.000000
d 1.000000
illum 1
map_Kd ../attendance/seating_popularity2.jpg
Level 3:
Ni 1.000000
d 1.000000
illum 1
map_Kd ../attendance/seating_popularity3.jpg
Level 4:
Ni 1.000000
d 1.000000
illum 1
map_Kd ../attendance/seating_popularity4.jpg
A couple quick notes:
1. Make sure your new stadium file is located in the ballparks/models folder before you change the .mtl file,
2. Every time you export the .obj file, you'll need to rewrite the code in the .mtl file.