Polish

Add new members to MouseMoveOperation, MMPanCamera and MMDollyCamera and their ...Start equivalents.

    typedef enum {
        MMNoOperation,
        MMPickAndTranslateObject,
        MMPickAndRotateObject,
        MMPickAndZTranslateObject,
        MMTranslateObject,
        MMRotateObject,
        MMZTranslateObject,
        MMRotateCameraStart,
        MMRotateCamera,
        MMPanCameraStart,
        MMPanCamera,
        MMDollyCameraStart,
        MMDollyCamera,
        MOUSEMOVEOPERATIONFORCEENUMSIZEINT = RWFORCEENUMSIZEINT
    } MouseMoveOperation;

Modify the mouse button code in win/events.c to enter these new modes according to whether the shift or control keys are held down. In the code below, shift enters the rotate camera mode, control the dolly mode, and neither, the pan mode. This was chosen to reflect the operations performed on atomics.

    static RsEventStatus
    HandleRightButtonDown(RsMouseStatus *mouseStatus)
    {
        /* Right mouse button down event handling... */
        if (mouseStatus->shift)
        {
            MouseMoveAction = MMRotateCameraStart;
        }
        else if (mouseStatus->control)
        {
            MouseMoveAction = MMDollyCameraStart;
        }
        else
        {
            MouseMoveAction = MMPanCameraStart;
        }
        return rsEVENTPROCESSED;

Next, in the Idle() function in main.c, add code to process these new modes. The code will be very similar to the MMRotateCameraStart mode. Call functions called DollyCamera() and PanCamera().

        case MMRotateCameraStart :
            RotateCamera(TRUE);
            MouseMoveAction = MMRotateCamera;
            break;

        case MMRotateCamera :
            RotateCamera(FALSE);
            break;

        case MMDollyCameraStart :
            DollyCamera(TRUE);
            MouseMoveAction = MMDollyCamera;
            break;

        case MMDollyCamera :
            DollyCamera(FALSE);
            break;

        case MMPanCameraStart :
            PanCamera(TRUE);
            MouseMoveAction = MMPanCamera;
            break;

        case MMPanCamera :
            PanCamera(FALSE);
            break;

Write the DollyCamera() and PanCamera() functions. These functions operate in an identical manner to the function we wrote earlier to rotate the camera. In both the new cases the functions access the current values of the camera's matrix and use the vectors to translate the camera. We will use up and down motion of the mouse to move the camera forward and backwards, and up and down and left and right movements to pan the camera. As we have done before we will convert movement of the mouse into dx and dy variables that are used to scale the vectors.

    static void
    DollyCamera(RwBool first)
    {
        RwFrame *f;
        RwV3d at;
        RwReal dy;
        if (!first)
        {
            f = RwCameraGetFrame(Camera);
            at = *RwMatrixGetAt(RwFrameGetMatrix(f));
            dy = OldPos.y - MousePos.y;
            RwV3dScale(&at, &at, dy*0.1f);
            RwFrameTranslate(f, &at, rwCOMBINEPOSTCONCAT);
        }
        OldPos = MousePos;

    /*
     *****************************************************************************
     */
    static void
    PanCamera(RwBool first)
    {
        RwFrame *f;
        RwV3d right, up, trans;
        RwReal dx, dy;
        if (!first)
        {
            f = RwCameraGetFrame(Camera);
            right = *RwMatrixGetRight(RwFrameGetMatrix(f));
            up    = *RwMatrixGetUp(RwFrameGetMatrix(f));
            dx = OldPos.x - MousePos.x;
            dy = OldPos.y - MousePos.y;
            RwV3dScale(&right, &right, dx*0.1f);
            RwV3dScale(&up,    &up,    dy*0.1f);
            RwV3dAdd(&trans, &up, &right);
            RwFrameTranslate(f, &trans, rwCOMBINEPOSTCONCAT);
        }
        OldPos = MousePos;

Compile and run the code. Confirm that your changes work as expected.

Now we will change the RotateCamera() function to support rotation of the camera about the x-axis as the mouse moves up and down. This will allow the camera to look up and down, as well as left and right.

Make the following changes to the RotateCamera() function:

    /* RotateCamera function */
    static void

    RotateCamera(RwBool first)
    {
        static const RwV3d xaxis = {1.0f, 0.0f, 0.0f};
        static const RwV3d yaxis = {0.0f, 1.0f, 0.0f};
        RwFrame *f;
        RwReal dx, dy;

        if (!first)
        {
            RwMatrix *m;
            dx = OldPos.x - MousePos.x;
            dy = OldPos.y - MousePos.y;

            f = RwCameraGetFrame(Camera);
            RwFrameRotate(f, &yaxis,  dx * 0.1f, rwCOMBINEPRECONCAT);
            RwFrameRotate(f, &xaxis, -dy * 0.1f, rwCOMBINEPRECONCAT);

        OldPos = MousePos;

Compile and run your code. Rotate the camera and make circular movements of the mouse in the middle of the window. You may well find that the camera tilts about the z-axis, although we have not written any code to make this happen. This is a common problem when two rotations are applied in axes in succession. After the first rotation is applied the second rotation is no longer about a perpendicular axis.

You may want to add the following code to this case statement to keep the camera from tilting as the rotations are applied. This code forces the camera's right vector to stay parallel to the world x-axis. The cross-products and normalizations are needed to ensure that the matrix remains orthogonal.

    /* RotateCamera function */
    static void

    RotateCamera(RwBool first)
    {
        static const RwV3d xaxis = {1.0f, 0.0f, 0.0f};
        static const RwV3d yaxis = {0.0f, 1.0f, 0.0f};
        RwFrame *f;
        RwReal dx, dy;

        if (!first)
        {
            RwMatrix *m;
            dx = OldPos.x - MousePos.x;
            dy = OldPos.y - MousePos.y;
            f = RwCameraGetFrame(Camera);
            RwFrameRotate(f, &yaxis,  dx * 0.1f, rwCOMBINEPRECONCAT);
            RwFrameRotate(f, &xaxis, -dy * 0.1f, rwCOMBINEPRECONCAT);

            m = RwFrameGetMatrix(f);

            RwV3dCrossProduct(&m->right, &yaxis, &m->at);
            m->right.y = 0.0f;
            RwV3dNormalize(&m->right, &m->right);
            RwV3dCrossProduct(&m->up, &m->at, &m->right);
            RwV3dNormalize(&m->up, &m->up);
            RwV3dCrossProduct(&m->right, &m->up, &m->at);
        }
        OldPos = MousePos;

Compile and run your code. You should find that with the code that you have added you can position the camera anywhere you want in the scene.

Polish [Tutorial 5 - Creating a World]

Polish
[Tutorial 5 - Creating a World]