FrameBufferHandler
FrameBufferInterface

Availability  LightWave® 6.0
Component  Layout
Header  lwframbuf.h

Frame buffer plug-ins display the current rendered frame, either on the screen or to another output device.

Handler Activation Function

   XCALL_( int ) MyFrameBuffer( int version, GlobalFunc *global,
      LWFrameBufferHandler *local, void *serverData );

The local argument to a frame buffer's activation function is an LWFrameBufferHandler.

   typedef struct st_LWFrameBufferHandler {
      LWInstanceFuncs *inst;
      LWItemFuncs     *item;
      int              type;
      LWError         (*open)  (LWInstance, int w, int h);
      void            (*close) (LWInstance);
      LWError         (*begin) (LWInstance);
      LWError         (*write) (LWInstance, const void *R, const void *G,
                                  const void *B, const void *alpha);
      void            (*pause) (LWInstance);
   } LWFrameBufferHandler;

The first two member of this structure point to the standard handler functions. In addition to these, a frame buffer also provides functions for the start and end of a rendering session, for receiving a frame's scanlines, and for displaying the frame, and it specifies what type of data it wants to receive.

type

The type of pixel data Layout should send to the write function. This can be either LWFBT_UBYTE or LWFBT_FLOAT.

error = open( instance, width, height )

Initialize the frame buffer. Called when a rendering session begins. Returns an error message string if an error occurs, otherwise it returns NULL.

close( instance )

Close the frame buffer. Called when the rendering session is complete.

error = begin( instance )

Prepare to receive the next frame. Returns an error message string if an error occurs, otherwise it returns NULL.

error = write( instance, R, G, B, alpha )

Receive the next scanline of the current frame. The scanlines for each frame are sent in order from top to bottom. The buffer arguments point to arrays of color channel values. There are exactly width values for each channel, one for each pixel in a scanline, and the values are either unsigned bytes or floats, depending on the type code. Returns an error message string or NULL.

pause( instance )

Pause awaiting user input. This is called for F9 and manually advanced frames, but not during automatic rendering. Typically the frame buffer displays the image here and then waits for the user to dismiss the display before returning from this function.

Interface Activation Function

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

This is the standard interface activation for handlers. A frame buffer's interface is invoked when the plug-in is selected as the render display on the Render Options panel.

Example

The framebuf sample is a simple example of a frame buffer. It uses the Raster Functions and Panels globals to store and display the rendered image.