In Corona Scatter, go to the Areas>Spline Excludes section and add your shape. By doing this, trees will scatter across the surface except within the boundaries set.

PRAGUE, Czech Republic, Oct. 17, 2022 (GLOBE NEWSWIRE) -- Today, Chaos launches Chaos Corona 9 for 3ds Max and Cinema 4D, accelerating the 3D design process with new tools for clouds, patterns, motion ...