Remove instanced geometry from specified areas

In the landscape scene, a number of grass clumps appear on the top of the rocky outcrops. You can paint a Ptex-based Density Mask so that no grass clumps generate on these areas.

See Control primitives with Ptex maps.

1. In the Generator Attributes section, click this icon beside Mask, and then select Create Map from the menu that appears.
2. In the Create Map window, type a name for the map such as mask_GrassClumps.
3. Set the following:
   • Map Resolution to 30.

     This sets the number of texels per-face for the Ptex map.

   • Start Color to White.

     This sets the map value to 1, which allows the geometry to be instanced on the surface. When painting on the mesh, you use black, which masks out these areas.

4. In the Tool Settings window, set the following:
   • Beside Artisan, select a hard-edged brush.
   • In the Color section, click the color swatch and select black.
   • In the Paint Operations sections, set Blend mode to Default.
   • In the Stylus Pressure section, turn off Stylus Pressure.
   Note: If the 3D Paint Tool window does not appear, click this icon in the Tool Box to open it.
5. Use the 3D Paint Tool to paint the areas of the mesh where you do not want to generate grass clumps.
6. Click this icon to save the Ptex map.
7. Preview the Description.

   Grass clumps no longer generate on the rocky areas of the landscape.