chapter 15: working with the camera

Chapter 15

Essentials of Interactive Computer Graphics: Concepts and Implementation K. Sung, P. Shirley, S. Baer

Chapter 15: Working with the Camera

Chapter 15


This Chapter: we will learn about One example of implementing

Computer Graphics Camera

Working with multiple Cameras

Examples of interactive camera manipulation

Select primitive in 3D scenes

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Changes to Library: 2D to 3D No changes:

Primitive: 2D primitives drawn in 3D SceneNode: continue to load MW Matrix Model: continue to be application main

class Changes:

WindowHandler When loading matrices!

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WindowHandler: 2D vs 3D

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Lib14: Support for 3D New classes:

Camera PrimitiveAxisFrame:

Drawing x,y,z axis frame Modifications:

WindowHandler Support Camera Load View and Projection Matrices

XformInfo Support 3D rotation

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Lib14: New Classes and Changes

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Lib14: The Camera Class

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Lib14: WindowHandler changes

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Lib14: XformInfo Changes Xform Operator in 2D

Scale, Translate, Pivot: all 3D quantity Problem:

Rotation: θ rotates wrt to z-axis! Xform Operator in 3D (for now)

Rotation: (θx θy θz) Three rotations with respect to each axes

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Lib14: XformInfo details …

Xform Operator:

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Tut 15.1: Working with Lib14 Using: Camera and WindowHandler

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Tut 15.1: WindowHandler details

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Lib14: D3D_WindowHandler

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Tut 15.1: DrawHandler

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Tut 15.1: Application CTutorialDlg

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Tut 15.2: Working with 2 Cameras

CTutorialDlg class

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Interactive Manipulation of Camera

Parameters under explicit user control Camera position Look at position

Parameters implicitly controlled Up Vector: try to maintain sense of “up”

Parameters typically not controlled Near/Far planes (no real-world correspondence) FOV – zooming control via camera position

movement

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Notation and Terminology

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Tut 15.3: Camera Manipulation with the Mouse

Left Mouse Button (LMB) Orbit

Middle (MMB) Pan

Right (RMB) Zoom

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LMB: Tumble or Orbit the Camera

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Left/Right Orbiting Axis of rotation: The “Up” Direction

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Up/Down Orbiting Axis or rotation: Side Vector

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Orbit: Idea Orbit or Rotate

Need Matrix:

Camera Position:

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Orbit: Alternatively

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Orbit: Implementation Rotate the World when compute

MV Instead of: Compute:

Compute and load:

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Lib14: Orbit Support Camera: mouse movement to

radians

And … using in WindowHandler

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Lib14: Using camera orbit info

In WindowHandler:: ComputeViewMatrix

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MMB: Pan or Track the camera

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Vertical Tracking: (Along UpVector)

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Tracking: Implementation Horizontal/Vertical mouse movements

dx and dy Computer Movement vector:

Left/Right tracking: along side-vector Up/down tracking: along up-vector

Update both camera and at positions:

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Lib14: Tracking Support Camera Class:

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RMB: Dolly or Zoom the Camera

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Zoom: Implementation Mouse movement: d Move camera eye position in the

viewing direction!

Watch out!

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Lib14: Mouse Zoom support Camera class

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Drawing the Camera Requires at least two Views!

View-A cannot draw the camera of View-A! Can only draw the camera for another

view! i.e., View-A draws camera of View-B

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Drawing camera: View Matrix Details

Recall: for “orbiting”, we computed and loaded MV with:

To properly draw camera-B, from view-A Include camera-B orbiting! Un-do view-A’s camera orbiting ( )

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Implementation: Load into the WORLD matrix

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3D DC to WC Transformation

Must: DC NDC EC WC

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Transform: DC to NDC Assume Recall:

Or: In 3D:

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DC Points and NDC Ray

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NDC Ray to EC Ray Transform

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NDC EC

If:

In general: or: Given:

Then:

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Reconstruct the ray in EC: Given: In general, NDC Point:

is a line in EC:

Or:

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EC to WC Transform: Given:

Choose convenient ze values ze= 0 and ze = 1

Use to compute WC positions:

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Tut 15.4: Mouse Click to WC Shift-LMB to see the selection ray

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Tut 15.4: Device to WC Xform

chapter 15: working with the camera

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