3D Graphics Programming with QuickDraw 3D 1.5.4

Creating Lights

When you use any renderer more powerful than the wireframe renderer, you'll want to create and configure a set of lights to provide illumination for the object in the model. As you've seen, QuickDraw 3D provides a number of types of lights, each of which can emit light of various colors and intensities. The function MyNewLights defined in Listing 6 creates a group of lights. It creates an ambient light, a point light, and a directional light. See the chapter "Light Objects" for more details on creating lights.

Listing 6 Creating a group of lights



 
TQ3GroupObject MyNewLights (void)

{

    TQ3GroupPosition                myGroupPosition;

    TQ3GroupObject                  myLightList;

    TQ3LightData                    myLightData;

    TQ3PointLightData               myPointLightData;

    TQ3DirectionalLightData         myDirLightData;

    TQ3LightObject                  myAmbientLight, myPointLight, myFillLight;

    TQ3Point3D                      pointLocation = { -10.0, 0.0, 10.0 };

    TQ3Vector3D                     fillDirection = { 10.0, 0.0, 10.0 };

    TQ3ColorRGB                     WhiteLight = { 1.0, 1.0, 1.0 };



 
    /*Set up light data for ambient light.*/

    myLightData.isOn = kQ3True;

    myLightData.brightness = .2;

    myLightData.color = WhiteLight;



 
    /*Create ambient light.*/

    myAmbientLight = Q3AmbientLight_New(&myLightData);

    if (myAmbientLight == NULL)

        goto bail;



 
    /*Create a point light.*/

    myLightData.brightness = 1.0;

    myPointLightData.lightData = myLightData;

    myPointLightData.castsShadows = kQ3False;

    myPointLightData.attenuation = kQ3AttenuationTypeLinear;

    myPointLightData.location = pointLocation;

    myPointLight = Q3PointLight_New(&myPointLightData);

    if (myPointLight == NULL)

        goto bail;



 
    /*Create a directional light for fill.*/

    myLightData.brightness = .2;

    myDirLightData.lightData = myLightData;

    myDirLightData.castsShadows = kQ3False;

    myDirLightData.direction = fillDirection;

    myFillLight = Q3DirectionalLight_New(&myDirLightData);



 
    if (myFillLight == NULL)

        goto bail;



    /*Create light group and add each of the lights to the group.*/

    myLightList = Q3LightGroup_New();

    if (myLightList == NULL)

        goto bail;

    myGroupPosition = Q3Group_AddObject(myLightList, myAmbientLight);

    Q3Object_Dispose(myAmbientLight);               /*balance the reference count*/

    if (myGroupPosition == 0)

        goto bail;

    myGroupPosition = Q3Group_AddObject(myLightList, myPointLight);

    Q3Object_Dispose(myPointLight);                 /*balance the reference count*/

    if (myGroupPosition == 0)

        goto bail;

    myGroupPosition = Q3Group_AddObject(myLightList, myFillLight);

    Q3Object_Dispose(myFillLight);                  /*balance the reference count*/

    if (myGroupPosition == 0)

        goto bail;



    return (myLightList);

    

bail:

    /*If any of the above failed, then return nothing!*/

    return (NULL);

}

The MyNewLights function is straightforward. It fills out the fields of the relevant data structures (TQ3LightData , TQ3PointLightData , and TQ3DirectionalLightData ) and calls the appropriate functions to create new light objects using the information in those structures. If successful, it adds those light objects to a group of lights. The group of lights will be added to a view, as shown in the following section.

The MyNewLights function can leak memory.