$NetBSD: patch-ac,v 1.1 2007/02/23 20:21:09 drochner Exp $

--- Rendering/vtkVolumeRayCastMapper.h.orig	2007-02-23 16:09:27.000000000 +0100
+++ Rendering/vtkVolumeRayCastMapper.h
@@ -80,6 +80,8 @@ inline int vtkRoundFuncMacro(double x)
         t1  = t10 + (y)*(t11-t10);  \
         v   =  t0 + (z)*(t1-t0);
 
+VTK_THREAD_RETURN_TYPE VolumeRayCastMapper_CastRays( void * );
+
 class VTK_RENDERING_EXPORT vtkVolumeRayCastMapper : public vtkVolumeMapper
 {
 public: