Collision objects

SpeedTree uses capsules as collision objects, providing a cruder representation of a tree object's shape than its detailed geometry. They have no polygonal resolution associated with them. Rather, they are mathematical representations, free to be passed into the collision-handling system in your application.

Capsules with the same two position values are treated as spheres.

The following code shows how to access the collision objects embedded in a CCore object, assuming it has been loaded.

#include "SpeedTree/Core/Core.h"
using SpeedTree::st_uint32;
 
void PrintCollisionObjects(const SpeedTree::CCore& cModel)
{
    st_uint32 uiNumObjects = cModel.CollisionObjects( ).Count( );
    for (st_uint32 i = 0; i < uiNumObjects; ++i)
    {
        SpeedTree::CCollisionObject cObject = cModel.CollisionObjects( )[i];
 
        printf("collision object [%d of %d]\n", i + 1, uiNumObjects);
 
        // each collision object has two position values; when they're identical,
        // the object is a sphere; when diferent, it's a capsule
        SpeedTree::Vec3 vPos1 = cObject.Position( );
        SpeedTree::Vec3 vPos2 = cObject.Position2( );
 
        if (vPos1 == vPos2)
            printf("  [Sphere]\n");
        else
            printf("  [Capsule]\n");
 
        printf("  position 1: (%g, %g, %g)\n", vPos1.x, vPos1.y, vPos1.z);
        printf("  position 2: (%g, %g, %g)\n", vPos2.x, vPos2.y, vPos2.z);
        printf("  radius: %g\n", cObject.Radius( ));
 
        // note the necessary (const char*) typecast
        printf("  user data: [%s]\n", (const char*)cObject.UserData( ).Data( ));
    }
}

The CForest object (in the Forest library) has a function, CForest::CollisionAdjust(), that will provide the functionality necessary to avoid running through a series of tree models. It works only within the SpeedTree framework but could serve as a useful start for your own application.