Project 3 : Animation COMP 341

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Project 3 AnimationCOMP 341
this ppt is at http//www.cse.ust.hk/weiwei/com
p341/lab_1.ppt
Grading sheet is at http//www.cse.ust.hk/weiwe
i/comp341/gradesheet.doc
Help Session I (TA Weiwei)
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Overview

• Project requirements
• Brief description
• Further Explanation
• Hints on the basic requirements

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Requirements

• Three curves with wrapping support
• Bezier (C0 continuity between segments)
• B-Spline
• Catmull-Rom
• Particle system
• Gravity another force simulator
• Baking (to cache frame information)
• You can hook your PS to your own model
• Animate your model in project 1 (For artifacts)

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Terms Curves(1)

• Draw a curve based on a set of given points
• E.g. a cubic bezier curve needs 4 points
• Parametric equations
• E.g. cubic bezier curve
• (t is the parameter, Ps are all vectors here)

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Terms Curves(2)

• More information about these curves
• Bezier curve
• http//en.wikipedia.org/wiki/BC3A9zier_curve
• http//www.cs.unc.edu/mantlter/research/bezier/
• B-Spline
• http//en.wikipedia.org/wiki/B-spline
• http//www.engin.umd.umich.edu/CIS/course.des/cis5
  77/projects/BSP/welcome.html
• Catmull-Rom curve
• http//www.mvps.org/directx/articles/catmull/

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Terms Wrapping

• The curve has C0 continuity (i.e. positional
  continuity) between the end and the beginning of
  the curve
• Solve the popping effect if the animation is
  looping (we use curves to guide the animation,
  x-axis is time, and y-axis is position or angle)
• Please study the line case given in the template
  (linecurveevaluator.cpp)

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Terms Particle Baking

• Cache the intermediate results of the particle
  system simulation to avoid re-computation
• Info needs to be cached whatever info needed
  for re-generation of this frame
• How to cache them in any ways you like

Baked region is automatically marked in the GUI
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Hints Curves(1)

• What you need to do
• Given the control points (Ctrl pts), compute all
  the evaluated points (Eval pts)
• Eval pts Just like a set of sampled points along
  the curve

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Hints Curves(2)

• How to generate the evaluated points?
• Evaluator every curve has its own evaluator
• Derived from class CurveEvaluator

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Hints Curves(3)

• More specifically Where should you write the
  code?

override this function

• INPUT
• control_points a sorted list of control points
• animation_length the maximum x value of the
  defined curve
• wrap_control_points the indicator about curve
  wrapping
• OUTPUT
• evaluated_curve_points a list of unsorted
  evaluated points
• TIPS
• dont forget to re-initialize the output
  parameter!

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Hints Curves(3 cont.)

• How to integrate your own evaluator classes into
  the existed code?
• Search TODO in GraphWidget constructor
• Modify following lines as you need

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Hints Bezier Curve

• Consecutive four control points generate a
  segments, C0 continuity between segments
• Add two horizontal lines to the start / end pt of
  the curve
• If the number of ctrl-pt is not enough to form a
  Bezier segment, draw a linear segment (one or
  two) instead.
• E.g. 3K1 points generate K segment(s)2
  horizontal lines
• E.g. 3K2 points generate K segment(s)2
  horizontal lines 1 line segment

C0 continuity
Segment 2
Segment 1
Straight line
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Hints B-Spline

• Special handling is required for the end points
• B-Spline doesnt pass through any control point.
• NOTE This is NOT the basic requirement. But you
  still should add start/end point to form a
  complete curve in some ways (curve or straight
  line, it is up to you)
• In the sample, the first/last endpoint is mapped
  to the first/last control point.

Sample exe
Normal B-Spline
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Hints Catmull-Rom

• Special handling is required for the convex hull
  problem
• The evaluated points may not monotonically
  increase in X)
• One possible solution is to abandon those turning
  back points

remove turning back evaluated points
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Hints Particle System(1)

• Your Tasks (by searching TODO)
• Implement all the functions in ParticleSystem.cpp
• Create your own particle class to store the
  property of the particle (partical.h/cpp)
• e.g. position, veolocity, force, mass, etc.
• Create a data structure to store the baked
  particles

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Hints Particle System(2)

• Important functions
• startSimulation() is called when you press the
  simulate button and start to play the animation
• computeForcesAndUpdateParticles() is called
  every time when the scene is drawn (in
  ModelerViewdraw()). You need to check if the
  variable simulate is true
• stopSimulation() is called when you press the
  simulate button again or the pause button
• bakeParticles() is called inside the function
  computeForcesAndUpdateParticles(). It is used to
  store the current configuration of the particles

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Hints Particle System(3)

• Baking data structure your own design, but
  generally you need to take care of
• particle positions for every time step when you
  replay it, you can avoid the re-simulation
• Time information When you change the number of
  frame per second (FPS), the particles should not
  run faster or slower

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Hints Particle System(3)

• How to integrate your own particle system?
• In main function, you can see
• Just follow the instruction, for example

ParticleSystem ps new ParticleSystem() //...do
some setup ModelerApplicationInstance()-SetPar
ticleSystem(ps)
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this ppt is at http//www.cse.ust.hk/weiwei/com
p341/lab_1.ppt
Grading sheet is at http//www.cse.ust.hk/weiwe
i/comp341/gradesheet.doc