Lec10 Computer Animation Techniques_2122.pdf

EIE 3101 Computer Animation Lec 10 Computer Animation Techniques 1 Isaac Kerlow, The art of 3D computer animation and effects, 4th ed., Hoboken, N.J.: John Wiley & Sons, 2009. Chapter 11 2021/22 sem 1 2 Content Ch11 Computer Animation Techniques Tutorial  Curve Editor Introduction  Interpol...

EIE 3101 Computer Animation Lec 10 Computer Animation Techniques 1 Isaac Kerlow, The art of 3D computer animation and effects, 4th ed., Hoboken, N.J.: John Wiley & Sons, 2009. Chapter 11 2021/22 sem 1 2 Content Ch11 Computer Animation Techniques Tutorial  Curve Editor Introduction  Interpolation  Path Constraint  LookAt Constraint  Bomb Space Warp  Material Animation 3 Computer Animation Techniques  Keyframing and forward kinematics are useful basic techniques for animating the position, orientation, shape, and attributes of 3-D characters.  In addition, using parameter curves to animate provides a powerful tool to sketch out and finetune character animation.  Other computer animation techniques include shape animation of 3-D models with lattice deformation or morphing, the interpolation of attributes like the surface characteristics of models, the depth of field of cameras, and the color of lights. 4 Morphing 5 FFD (Free-Form Deformation) Modifiers in 3ds Max https://knowledge.autodesk.com/support/3ds-max/learnexplore/caas/CloudHelp/cloudhelp/2016/ENU/3DSMax/files/GUID-1129177A-6B3D-47EB-8636-B6D38BE816F8-htm.html 6 Keyframe Interpolation  Hallmark of animation: defining keyframes with key poses and creating the in-between positions.  Keyframe interpolation: computer animation technique used to create in-between positions.  Keyframe interpolation calculates the inbetween frames by averaging the information specified in the keyframes (Fig 11.1.1)  Interpolation techniques can be used to calculate the position of objects in space, as well as their shape and other attributes.  The most common types of interpolation include linear and curve interpolation. 7 8 Keyframe Interpolation  Establishing a keyframe is usually done interactively, using an animation timeline that stores position and duration of the different moments and actions being animated.  Interpolating keyframes allows us to control the time, or speed, that it takes to get from one keyframe to another and the rate of change between frames (Fig 11.1.2) 9 Keyframe Interpolation  Interpolation is commonly expressed in the form of a graph that shows the relation between time and the parameter being animated.  Time is usually represented by the horizontal axis, and the parameter in question is usually represented by the vertical axis.  The slope of the path in the graph represents the speed or rate of change. (Fig 11.1.3)  Interpolation graphs are generated automatically by most computer animation software as soon as the animator specifies the animation parameters on one or several objects in the scene.  It is usually possible to edit these graphs interactively. 10 Fig 11.1.3-11.1.5 11 Linear Interpolation  Linear interpolation simply averages the parameters in the keyframes and provides as many equally spaced in-between frames as needed.  Constant speed is represented by the straight lines in the graph.  Fig 11.1.4 12 Curved Interpolation  Curved interpolation, also called an interpolation ease, is a technique for calculating in-between frames that is more sophisticated than linear interpolation.  Curved interpolation averages the parameters in the keyframes, taking into account the variations of speed over time, known as acceleration.  Ease in (increase in speed) is represented by a line that curves up. (Fig 11.1.5)  Ease out (decrease in speed) is represented by a line that curved down. (Fig 11.1.3)  Therefore, the distribution of in-between frames along the path depends on whether rate of change increases or decreases.  Curved interpolation can also include motion with constant speed. (Fig 11.1.4) 13 Working with Parameter Curves  A graph representing curved interpolations is also called a parameter curve or a function curve.  These graphs are generated automatically by computer animation software as the animator moves the object. (Fig 11.1.9A)  Working with parameter curves provides animators with an additional method for modifying the animation.  The exact shape of a function curve depends on the type of curve used (Fig 11.1.6) 14 Fig 11.1.6, 11.1.9A 11.1.9A 50% ease in and 50% ease out 15 Working with Parameter Curves  Parameter curves can represent either a simple linear interpolation, an ease in, or an ease out.  These complex interpolations can be defined interactively, e.g. by dragging a slider that represents the proportion of ease in, linear, and ease out in the function. 16 Camera Animation  The camera plays an important role in computer animation because its motion and the changes in some of its attributes can have a powerful storytelling effect.  All camera motions require a change in the position and orientation of the camera.  In addition, the focal length and depth of field are some of the attributes that can be easily animated. 17 Position Camera moves  The position of a camera can be easily defined by typing an absolute position value specified in XYZ world coordinates  This technique can be useful for defining locked shots, where the camera must be still and in a precise location.  However, a more intuitive way to define the position of a camera consists of using the interactive controls to build compound moves. 18 Position Camera moves  The 3 camera moves that are based on a change of the position of the camera include a dolly, a truck, and a boom (Fig 11.3.1a)  A truck is a translation of the camera along the horizontal axis  A truck moving along with a subject, following and tracking it is also called a traveling shot (Fig 11.3.5)  A dolly move is a translation of the camera along the depth axis, and is useful for going in or out of the scene.  A boom is a translation of the camera along vertical axis. Fig 11.3.1a, 11.3.5 19 TRUCK DOLLY BOOM 20 Orientation Camera Moves  The orientation of a camera can be easily defined with an absolute XYZ position value when the camera has a locked point of interest or must be looking in a precise direction.  The camera moves that are based on the change of the orientation of the camera include a tilt, a roll, and a pan.  A tilt is a rotation of the camera on its horizontal axis. Also called a pivot and is used to look up or down.  A roll is created by rotating camera around it Z axis. Roll camera moves are common when simulating flythroughs.  A pan is a move created by rotating the camera around its vertical axis. (Fig 11.3.1b) Panning is effective for scanning the scene from side to side while the camera remains stationary.  A zoom is a camera move that is achieved not by moving the position or orientation of the camera but by animating the focal length of its lens (Fig 7.4.3). 21 Fig 11.3.1b PAN TILT ROLL 22 Crane shot • A crane shot can be implemented with a combination of position and orientation camera moves. (Fig 11.3.2) • Crane shots with computer-simulated cameras are not bound by many of the physical obstacles. By Ken123 - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=4108079 23 Fig 11.3.2 24 Camera Motion Paths  The motion path technique works by animating an object—the camera in this case—along a path defined in 3-D space.  The paths are drawn with a simple curve modeling tool and edited just as any other object in 3-D space would be edited.  Once a camera is linked to the motion path and once the initial timing parameters of the path are defined, then it is possible to refine the timing, speed, and acceleration with the animation curves (interpolation graph).  Motion path animations can be enhanced with variable speeds, ease ins, and ease outs 25 Focal Length and Zoom Camera Moves  The focal length of a camera controls the way in which 3-D objects are seen by the camera.  The focal length in a virtual camera is defined by the relation between the near clipping plane and the far clipping plane.  This relation defines the way in which the objects in a 3-D environment are projected onto the projection plane of a virtual camera.  A zoom can be considered a camera move where the camera remains still but the framing of the image changes by gradually and continuously modifying the camera’s focal length.  In a zoom camera move, both the position and orientation of the camera remain untouched. 26 Fig 7.2.1 from Lec04 Camera 27