1. 고려대학교 그래픽스 연구실 Cameras and Lights - The Inventor mentor 고려대학교 그래픽스 연구실 2001.8.8 민 성환

2. 19 February 2016Sunghwan Min 2 Using Lights and Cameras  Two classes of nodes that affect how the 3D scene appears : light and cameras  Inventor provides different classes of lights for you to use in your scene  Light bulbs  The sun  Theatrical spotlights  Cameras are our “eyes” for viewing the scene

3. 19 February 2016Sunghwan Min 3 Cameras  A camera node generates a picture of everything after it in the scene graph  A scene graph should contain only one active camera  Camera position in space is affected by the current geometric transformation

4. 19 February 2016Sunghwan Min 4 SoCamera  Abstract base class  Fields  viewportMapping – treatment when the camera’s aspect ratio is different from the viewport’s aspect ratio  position – location of the camera viewpoint  orientation – describes how the camera is rotated  aspectRatio – ratio of the camera viewing width to height  nearDistance  farDistance  focalDiatance – distance from the camera viewpoint to the point of focus (used by the examiner viewer) ??

5. 19 February 2016Sunghwan Min 5 SoCamera  Methods  pointAt(const SBVec3f &targetPoint) – replace the value in a camera’s orientation field  viewAll(SoNode *sceneRoot, const SbViewportRegion &vpRegion, float slack =1.0) – set the camera to view an entire scene graph  The slack parameter is used to position the near and far clipping planes  getViewVolume – return the camera’s view

6. 19 February 2016Sunghwan Min 6 Subclasses of SoCamera  SoPerspectiveCamera  Field  heightAngle – specifies the vertical angle in radians of the camera view volume –widthAngle= heightAngle*aspectRatio

7. 19 February 2016Sunghwan Min 7 Subclasses of SoCamera (cont.)  SoOrthographicsCamera  Field  Height

8. 19 February 2016Sunghwan Min 8 Mapping  Mapping the Camera Aspect Ratio to the Viewport  A viewport is the rectangular area where a scene is rendered  Allows you to specify how to map the camera projection into the viewport when the aspect ratios of the camera and viewport differ  Crop the viewport to fit the camera projection  CROP_VIEWPORT_FILL_FRAME  CROP_VIEWPORT_LINE_FRAME  CROP_VIEWPORT_NO_FRAME

9. 19 February 2016Sunghwan Min 9 Mapping (cont.)  Adjust the camera projection to fit the viewport  ADJUST_CAMERA – the projected image is not distorted  LEAVE_ALONE – the camera image is resized

10. 19 February 2016Sunghwan Min 10 Viewing a Scene with Different Cameras  Example 4-1 shows a scene viewed by an orthographic camera and two perspective cameras in different positions.It uses a blinker node

11. 19 February 2016Sunghwan Min 11 Example 4-1  주요 코드 SoBlinker *myBlinker = new SoBlinker; root->addChild(myBlinker); // Create three cameras. Their positions will be set later. // This is because the viewAll method depends on the size // of the render area, which has not been created yet. SoOrthographicCamera *orthoViewAll =new SoOrthographicCamera; SoPerspectiveCamera *perspViewAll = new SoPerspectiveCamera; SoPerspectiveCamera *perspOffCenter =new SoPerspectiveCamera; myBlinker->addChild(orthoViewAll); myBlinker->addChild(perspViewAll); myBlinker->addChild(perspOffCenter);

12. 19 February 2016Sunghwan Min 12 Example 4-1 // Establish camera positions. // First do a viewAll on all three cameras. // Then modify the position of the off-center camera. SbViewportRegion myRegion(myRenderArea->getSize()); orthoViewAll->viewAll(root, myRegion); perspViewAll->viewAll(root, myRegion); perspOffCenter->viewAll(root, myRegion); SbVec3f initialPos; initialPos = perspOffCenter->position.getValue(); float x, y, z; initialPos.getValue(x,y,z); perspOffCenter->position.setValue(x+x/2., y+y/2., z+z/4.);

13. 19 February 2016Sunghwan Min 13 Lights  A scene graph also needs at least one light (with the default lighting model : Phong)  Determines two things  What the light illuminates  Where the light is located in 3D space ( location or direction)  All light-source nodes is that lights accumulate  Each time you add a light to the scene graph,the scene appears brighter

14. 19 February 2016Sunghwan Min 14 SoLight  The abstract base class for All lights  Fields  on (SoSFBool) – whether the light is on  intensity (SoSFFloat) – brightness of the light (0.0 ~ 1.0)  color (SoSFColor) – color of the light

15. 19 February 2016Sunghwan Min 15 Subclasses of SoLight  Subclass  SoPointLight  SoDirectionalLight  SoSpotLight  Computation cost  Directional light < Point light < Spot light

16. 19 February 2016Sunghwan Min 16 SoPointLight  Like a star,radiates light equally in all directions from a given location in 3D space  Additional field  Location (SoSFVec3f) – 3D location of a point light source

17. 19 February 2016Sunghwan Min 17 SoDirectionalLight  Illuminates uniformly along a particular direction  Since it is infinitely far away, it has no location in 3D space  Additional field  Direction (SoSFVec3f) – specifies the direction of the ray from a directional light source  All rays of incident light are parallel

18. 19 February 2016Sunghwan Min 18 SoSpotLight  Illuminate from a point in space along a primary direction  Like a theatrical spotlight, its illumination is a cone of light diverging from light’s position

19. 19 February 2016Sunghwan Min 19 SoSpotLight (cont.)  Additional fields  Location (SoSFVec3f)  Direction (SoSFVec3f)  dropOffRate (SoSFFloat)  Rate at which the light intensity drops off from the primary direction (0.0 =constant intensity, 1.0=sharpest drop-off)  cutOffAngle (SoSFFloat)  This angle is measured from one edge of the cone to the other

20. 19 February 2016Sunghwan Min 20 Using Multiple Lights  You can now experiment by adding different lights to a scene  Example 4-2 contains two light sources

21. 19 February 2016Sunghwan Min 21 Example 4-2 // Add a directional light SoDirectionalLight *myDirLight = new SoDirectionalLight; myDirLight->direction.setValue(0, -1, -1); myDirLight->color.setValue(1, 0, 0); root->addChild(myDirLight); // Add the point light below the transformSeparator SoPointLight *myPointLight = new SoPointLight; myTransformSeparator->addChild(myPointLight); myPointLight->color.setValue(0, 1, 0);