How to Use Cloth Pressure for Inflatables in Blender

This guide explains how to use the Cloth simulation's Pressure setting in Blender to create realistic inflatable objects like balloons, cushions, and pool floats. By configuring a closed 3D mesh, enabling cloth physics, and adjusting the internal pressure parameters, you can quickly simulate expanding, airtight objects without complex manual modeling.

1. Prepare the Base Mesh

  1. Add or model a closed 3D object (such as a UV Sphere, Cube, or a custom low-poly model).
  2. Ensure the mesh has clean, evenly distributed topology. Add a Subdivision Surface modifier or manually subdivide the mesh in Edit Mode to provide enough geometry for the cloth to bend.
  3. Check face normals by entering Edit Mode, selecting all faces (A), and pressing Shift + N to ensure all normals face outward. An inverted normal will cause the pressure to collapse the object rather than inflate it.

2. Enable the Cloth Modifier

  1. Select your object and navigate to the Physics Properties tab on the right-hand panel.
  2. Click on Cloth to add the simulation modifier to the object.
  3. In the Cloth settings, expand the Physical Properties section. You can leave the base settings at default or select a preset like Silk or Rubber depending on the stiffness you want for the outer skin.

3. Configure the Pressure Settings

  1. Scroll down within the Cloth settings to find the Pressure panel and check the box to enable it.
  2. Adjust the key pressure parameters:
    • Pressure: Set a positive value (e.g., between 2.0 and 10.0) to force the mesh outward. Higher values create a stiffer, more inflated look.
    • Custom Volume: Check this if you want the object to target a specific volume rather than continuously expanding.
    • Pressure Scale: Adjust this to control how quickly the pressure builds up during the animation.

4. Adjust Gravity and Collisions

  1. If you want the object to inflate on a surface, add a floor plane and assign a Collision modifier to it from the Physics tab.
  2. In the Cloth settings under Field Weights, reduce Gravity to 0 if you want the object to float, or leave it at 1.0 if it should rest on a collision surface.
  3. Expand the Collisions panel in the Cloth settings and check Self Collisions to prevent the mesh from intersecting with itself during inflation.

5. Run and Bake the Simulation

  1. Return to frame 1 and press Spacebar in the Timeline to play the simulation and observe the inflation.
  2. If the shape wrinkles too much, increase the Tension and Compression values in the Stiffness section.
  3. Once satisfied with the result, open the Cache panel in the Cloth settings and click Bake to lock in the simulation data.
  4. Add a Subdivision Surface modifier below the Cloth modifier in the Modifier stack and enable Shade Smooth for the final render.