5.8Inflatables and Closed Shells

• Keep a shape. Add Tnpix Volume with Mode Keep volume and Volume ratio 1.0: a ball stays a ball, a pillow keeps its fill. Raise Softness to let contact squash it and recover over time.
• Inflate or deflate. Animate Volume ratio (1.3 inflates by 30 percent) or use Pressure mode and animate Pressure.
• Float. Turn on Buoyancy; Lift 1.0 hovers, above 1 rises.
• Keep a region. Paint the area in a Tnpix Channel, such as a character's belly, and set it as the Volume's Channel. Pick a bone inside it as the Centre so the region keeps its volume around the bone as the body moves; paint a soft edge so it blends into the rest of the skin. Add one Tnpix Volume per region.

A whole object's mesh must be closed; a painted region need not be. Each object needs its own Volume modifier; on a shared Solver each garment keeps its own volume.