DisplacementHandler
DisplacementInterface

Availability LightWave 6.0 | Component Layout | Header lwdisplce.h

Displacement plug-ins deform objects by moving their points at each time step.

Handler Activation Function

   XCALL_( int ) MyDisplacement( long version, GlobalFunc *global,
      LWDisplacementHandler *local, void *serverData );

The local argument to a displacement plug-in's activation function is an LWDisplacementHandler.

   typedef struct st_LWDisplacementHandler {
      LWInstanceFuncs *inst;
      LWItemFuncs     *item;
      LWRenderFuncs   *rend;
      void            (*evaluate) (LWInstance, LWDisplacementAccess *);
      unsigned int    (*flags)    (LWInstance);
   } LWDisplacementHandler;

The first three members of this structure are the standard handler functions. The context argument to the inst->create function is the LWItemID of the object associated with this instance.

In addition to the standard functions, a displacement plug-in provides an evaluation function and a flags function.

evaluate( instance, access ): This is where the displacement happens. At each time step, the evaluation function is called for each vertex in the object. The position of the vertex is examined and modified through the access structure described below.
f = flags( instance ): Returns bit flags combined using bitwise-or. The flags tell Layout whether the displacement will be in world coordinates and whether it should occur before or after the object has been deformed by bones. Only one of these flags should be set.
LWDMF_WORLD LWDMF_BEFOREBONES

Interface Activation Function

   XCALL_( int ) MyInterface( long version, GlobalFunc *global,
      LWInterface *local, void *serverData );

This is the standard interface activation for handlers.

Displacement Access

The LWDisplacementAccess passed to the evaluation function contains two point positions, the point ID, and a mesh info for the object the point belongs to.

   typedef struct st_LWDisplacementAccess {
      LWDVector    oPos;
      LWDVector    source;
      LWPntID      point;
      LWMeshInfo  *info;
   } LWDisplacementAccess;

oPos: The original point location in object coordinates. This is read-only.
source: The location to be transformed in place by the displacement. If the flags function returned the LWDMF_WORLD bit, the source is in world coordinates and has already been modified by morphing, bones and object motion. Otherwise the source is in object coordinates (after morphing, before item motion, and before or after bone effects, depending on whether the flags function returned LWDMF_BEFOREBONES).
point: The point ID. This can be used to retrieve other information about the point from the mesh info structure.
info: A mesh info structure for the object.

History

In LightWave 7.0, LWDISPLACEMENT_VERSION was incremented to 5. This reflects additions to the LWMeshInfo structure, but in all other respects, displacement handlers were unchanged.

Example