While yarn type and pile height certainly have an effect on vertical ball rebound, infill depth and infill height are the two most important factors.

Impact on Vertical Ball Rebound

Vertical ball rebound chart
-- according to Dow research

General Characteristics Dow Products Qualities Results
Yarn Type The yarn type and design can have an effect on the vertical ball rebound as a result of the yarn resilience and stiffness properties as well as its bend resistance characteristics. DOWLEX™ Polyethylene Resins, ELITE™ Enhanced Polyethylene Resins Softness, resiliency, weatherability (UV resistance), mechanical toughness Long durability for play consistency
Pile Height Pile height has a minor influence on ball rebound. In principle, the higher is the pile the lower will be the ball rebound, while the harder the pile the higher will be the ball rebound. Your Dow product choice for yarn type will contribute to desired pile height.
Infill Type

The hardness and stiffness of the infill type, be it silica sand or rubber granules, has a significant impact on ball rebound.

After the pile, the infill material is the main resisting mass for the ball. Consequently, the right balance between soft and hard properties needs to be achieved as to obtain the required energy absorption level, infill softness and deformation characteristics.

VERSIFY™ Plastomers & Elastomers, ENGAGE™ Elastomers Overall flexibility, good balance, softness Required energy absorption level is obtained, as much as the required deformation characteristics
Infill Depth Infill depth will have a direct impact on the vertical ball rebound where the higher this layer of infill, the lower the ball rebound. Your Dow product choice for infill type will contribute to desired infill depth.