Possibly a javascript compile error that passes on your desktop, but not mobile? See related dicussion:
If not, a quick test: If you change draw3Ddirect, does the sketch display something on iOS? For example, try using it to draw simple boxes without textures, or to draw 2D shapes. My guesses to start looking would be some issue with iOS and texture, renderer, or specific canvas / PGraphics sizes / aspect ratios.
How are you viewing it on iOS – through the editor link?