Cameras and Light
Chapter 4, The Inventor Mentor
Camera structure
Focal length
Image
plane
Camera nodes
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•
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Camera node should be near the top left
Camera node generates a picture after it
A scene should contain only one camera
The camera position is set by current trans.
Viewport – rectangular rendered area
How can we use more than one camera?
Built-in viewer
• Using viewer (predefined camera)
– SoWinExaminerViewer * viewer = new
SoWinExaminerViewer(window);
– viewer->setSceneGraph(root);
– viewer->show();
• Using your own window
– SoWinRenderArea *myRenderArea = new
SoWinRenderArea(window);
– root -> addChild(myCamera)
– myCamera->viewAll(root, myRenderArea>getViewportRegion());
– myRenderArea->setSceneGraph(root);
– myRenderArea->show();
Perspective camera
widthAngle =
heightAngle*aspectRatio
Orthographic camera
width = height*aspectRatio
Orthographic – Perspective
SoCamera
• viewportMapping (SoSFEnum)
– How to map camera to the viewport
– Adjust the viewport (dead space remains)
• CROP_VIEWPORT_FILL_FRAME
• CROP_VIEWPORT_LINE_FRAME
• CROP_VIEWPORT_NO_FRAME
– Adjust the camera to fit the viewport (default)
• ADJUST_CAMERA
• Temporarily override aspectRatio
– Adjust the image (distortion)
• LEAVE_ALONE
SoCamera
•
position (SoSFVec3f)
– Location of the camera viewpoint (origin).
– Modified by the current transformation.
•
orientation (SoSFRotation)
– Orientation of camera’s viewing direction (V).
– Camera rotation with respect to the default.
The default position and orientation of a camera is at
(0,0,1) looking along the negative z-axis. The up
direction is (0, 1 ,0).
SoCamera
•
aspectRatio (SoSFFloat)
– Ratio of the camera viewing width to height.
– Must be greater than 0
– SO_ASPECT_SQUARE = 1/1
– SO_ASPECT_VIDEO = 4/3
– SO_ASPECT_HDTV = 16/9
•
nearDistance (SoSFFloat)
– Camera viewpoint to the near clipping plane.
SoCamera
•
farDistance (SoSFFloat)
– Camera viewpoint to the far clipping plane.
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focalDistance (SoSFFloat)
height / heightAngle (SoSFFloat)
SoCamera functions
• void pointAt(SbVec3f &target)
– Sets the orientation towards specific target
• void viewAll(SoNode *root, SbViewportRegion
&vpRegion, float slack = 1.0)
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View the entire scene
Orientation does not change
Position, near distance and far distance change
SbViewportRegion vpRegion(myRenderArea->getSize());
Example
Lights in Inventor
• Light node in Inventor determines
– What the light illuminates (following nodes)
– Where it is located (affected by current
transformation)
• Light sources are cumulative
• SoTransformSeparator
– Light should not be under standard separator
– You can separate only light transformation
– Only the light position can be changed
Light Nodes
• SoLight fields
– On (SoSFBool)
• If the source is turned on / off
– Intensity (SOSFFloat)
• 0 – minimum
• 1 – maximum
– color (SOSFColor)
• Color of the light
Light Nodes
• SoPointLight (Point Source)
–
location (SoSFVec3f)
• 3D location of a point light source
• affected by current geometric transformation
Light Nodes
• SoDirectionalLight (Parallel source)
– direction (SOSFVec3f)
• Direction of rays
• Affected by current transformation
Light Nodes
• SoSpotLight
– A point light restricted to a cone
– location (SoSFVec3f)
• 3D location of a point light source
• affected by current geometric transformation
–
direction (SoSFVec3f)
• primary direction of illumination
–
dropOffRate (SoSFFloat)
• rate at which the light intensity drops off from the primary
direction.
• 0.0 = constant intensity
• 1.0 = sharpest drop-off
Light Nodes
•
cutOffAngle (SoSFFloat)
– angle, in radians, where the intensity is 0.0
– measured from one cone edge to the other
Light Nodes
• Directional lights are the fastest
• Spotlights are the slowest
• To increase speed use fewer lights
Multiple Lights Example
• The example contains:
– A red stationary directional light
– A green light moved back and forth by SoShuttle