   light and mesh
  i would create a light and point it to my object scenegraph node.I find this code for wild magic4 engine :    m_spkCamera->SetFrustum(60.0f,1.0f,0.1f,100.0f);    Vector3f kCLoc = Vector3f(8.0f,0.0f,4.0f);    Vector3f kCDir = -kCLoc;  // lookat origin    kCDir.Normalize();    Vector3f kCUp(kCDir.Z(),0,-kCDir.X());    Vector3f kCRight = Vector3f::UNIT_Y;    m_spkCamera->SetFrame(kCLoc,kCDir,kCUp,kCRight);Wm4::LightPtr spkLight = WM4_NEW Light(Light::LT_DIRECTIONAL);    spkLight->Ambient = ColorRGB(0.75f,0.75f,0.75f);    spkLight->Diffuse = ColorRGB::WHITE;    spkLight->Specular = ColorRGB::WHITE;    float fValue = -Mathf::Sqrt(1.0f/3.0f);    spkLight->DVector = Vector3f(+fValue,+fValue,+fValue);but i'm not understand how positioning the mesh for view it and point the light on it.thanks.   
  I would understand a method for positioning the camera, and point it to a bounding box in opengl.I have the spheric bounding box , with a radius , how i center the camera on it ,  and how i point the light on it(the bounding box)?Thanks.;  I'm not sure I fully understand what you need exactly nor don't I know the Wild Magic 4 API. However, I'll try and explain the way this would be done in OpenGL.(0. set the projection matrix, I guess this would correspond to m_spkCamera->SetFrustum(60.0f,1.0f,0.1f,100.0f); ) // you can do this once when initializing your scene or on each window resize event etc.1. setup the current view matrix, e.g. by using gluLookAt which lets you define the position of the camera and the point the camera is looking at (i.e. your mesh's position) //keep in mind that the distance from the camera to the mesh as well as your settings for the near and far planes also have an influence on whether your mesh will be visible2. set your lights' positions //Note that for a directional light (LT_DIRECTIONAL) you don't have a position, just a direction. So just set that direction to the normalized direction from your light to your mesh, i.e. normalize(posmesh-poslight);;  thanks a lotbutQuote:2. set your lights' positions //Note that for a directional light (LT_DIRECTIONAL) you don't have a position, just a direction. So just set that direction to the normalized direction from your light to your mesh, i.e. normalize(posmesh-poslight);1)and for the directional light how i can calculate the direction that center my mesh?and mostly , how i can have a light that follow my mesh in the scene.I must use a spot light for this?2)How i fit my mesh in all camera space?I have a spheric bounding volume of the mesh...by evil!   ;  To 1) Depends on what you want to do. What do you mean with "light that follow my mesh in the scene"? Should it always light the same side? Should it be at the same location related to your mesh? If the part of the mesh that faces the camera should always be lit, the light's direction is just the direction from the camera to the mesh, i.e. mesh.pos-camera.pos. At the beginning of each frame, calculate the direction and set it after setting up the view matrix.To 2) You problem could be reformulated as finding the position inside the pyramid described by the frustum such that the bounding sphere centered at that position touches the frustum. Since landscape frustums (i.e. width > height) are the more common case, you'd want to find the look at position for your camera (provided that position is mapped to the screen center) so that the distance from that position to the frustums top or bottom plane is equal to the radius of the sphere, which you can express in 2D using a triangle. (I don't have an image, so it might help to draw it on a paper for better understanding.)Thus, using simple trigonometry (length of side a / length of side b = sin(alpha)/sin(beta)), you can calculate the distance to the camera: d = radius/sin(fov) //you might need to multiply fov with 0.5 or height/width, depending on how it is definedYou also might want the mesh to be placed at least 'radius' units from the near plane in order to not have parts of it being cut. Thus the real distance from the camera would be d' = max(d,near+radius);Using that distance you can place the object at camera.position + d * camera.forward. (note: camera.forward needs to be normalized, i.e. have length 1)Hope that helps. (Note: There might be simpler methods, that I'm not aware of.)