physics_material.h

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#pragma once
#include <engine/engine_export.h>
 
#include <memory>
 
#include <type_traits>
 
namespace unravel
{
 
//------------------------------------------------------------------------------
// 1) Enum for per-body combine modes.
//    We assign explicit integer values so they map neatly into userIndex2.
//------------------------------------------------------------------------------
enum class combine_mode : int
{
    average = 0,  // PhysX default: (eA + eB)/2
    minimum = 1,  // min(eA, eB)
    multiply = 2, // Bullet default: eA * eB
    maximum = 3,  // max(eA, eB)
    count = 4
};
 
struct physics_material
{
    using sptr = std::shared_ptr<physics_material>; 
    using wptr = std::weak_ptr<physics_material>;   
    using uptr = std::unique_ptr<physics_material>; 
 
    float restitution{0}; 
 
    float friction{0.5}; 
 
    float stiffness{0.5}; 
 
    float damping{0.1f}; 
 
    combine_mode restitution_combine{combine_mode::average}; 
 
    combine_mode friction_combine{combine_mode::average}; 
 
    auto get_stiffness() const -> float
    {
        const float min_stiffness = 1e3f; 
        const float max_stiffness = 1e5f; 
        return min_stiffness + stiffness * (max_stiffness - min_stiffness);
    }
};
 
} // namespace unravel