Camera angles

• By Chris Hinkey (cmh209)

• Standard game camera angle techniques

• Camera controllers

• Replay camera angles

• Don’t need to do much if the game is in 2D

• When your game is 3D and dynamic is when some problems come in

Why we need a good camera system

• If done right cameras will not be noticed • If done wrong everyone will notice the

slightest flaw • Jittery cameras are not good for fun game

play• If you can not see the hero well it is hard

to react successfully • Having to fix the camera manually as a

user is annoying

Requirements of a good camera system

• Able to change from user input • Continuously see a clear view of the desired

character. • Give special attention to important events • Anticipate characters movements as well as

possible• Have a clear view of the path of the character

Problems with doing this

• Not able to pre-process the environment

• Not able to hard code where the camera needs to go

• Avoid obstacles from being in between the camera and the character

Avoiding obstructed view

• How to do this, pros and cons

– Raycast collisions

– Multi-raycast

Attraction points

• The camera moves to different pre defined points depending on where the character is located

• Works well for small maps• Could possibly cause a jittery camera• Doesn't work as well with a dynamic

environment

Raycast collisions

• Cast out one ray from the character to the camera

• Set the camera from any clear path in between the camera and the character

• This causes sudden camera movements

• Some ways around this?

Multi-raycast

• Send out four rays from the character around where the camera should go

• Should the camera move away from object?– If any of the four rays is hit by an object move away from that

object

• Should the distance be shortened?– If a clear path can be obtained zoom in

More on Multi-raycasts

• Smoothing– Used to deal with tunnel situations – Use more zooming in to get around obstacles

• Camera transitions (switching characters)– a function occurs to calculate the new

camera position for the new character.

Intelligent Camera Control

• Typical architectures and the problems

• A better way to build a camera control system

Typical camera architectures

• Starts with a few monolithic behaviors that only work well for predictable behaviors

• Then fixes are added for certain cases where the camera is broken

• This causes a very fragile camera system to code

• Trade off between fixing a problem and possibly breaking something else

• This focuses more on the subject not the camera

A better way to do things

• The camera should be thought of as a primary character

• Should be based on lightweight behaviors to allow easy design process

• Easy addition of new behaviors• Easy way to switch between these behaviors

• How do we do all this

Implementation

• Camera fragment class – Simple math processor– Camera behavior– Updates camera every frame – Receives camera location matrix and

generates the new camera position – Generalized code that can be reused in many

projects

Camera Fragment class

• Three update components – position– Height with respect to terrain – Look at and field view (make sure object is in

view)• These are to be preformed in order

Implementation continued

• Camera Controller class– An interface between the game and the Camera

Fragment class – In charge of creation/destroying, ordering, activation

and updates to different fragments– Will create fragments and put them in a specified

order – During each update the controller will cascade

through the fragments and generate a new location– No way to turn fragments on and off

Adding some AI

• There is some lack of flexibility, lets fix that • Rules

– Add rules that turn fragments on and off– Used within both controller and fragment classes– Fuzzy rules would add a level of flexibility (too close,

not too far)– Works better for systems with fewer fragments – Hard to reorder fragments using this technique

State Machines

Controller class can have a simple Machine having a rule set to traverse through the states

• Each state can be a set of fragments that are active

• Allows easy reordering of fragments

Other AI

• Messaging – This is a good way to keep track of game data in the

controller class without using a lot of processing time – Used to trigger rule system

• Scripting– Can abstract out code for messaging, switching and

ordering– Helpful for doing replays

Camera angles in replays

• Important for sports games • Give the player the ability to see some of

the minor details of the game• Common problems • Different styles

Problems

• Player must be entertained continuously

• Frustration – Accuracy (use better recording schemes )– Poor performance– Player must feel in control of the replay

• Restart, pause, speed control, jump forward and back, and change camera

More problems

• Boredom

– Have a fast paced interesting replay – This is hard to do because you need to create

the replay on the fly – A rule based AI system can help in this– These rules can be based on film making

camera work

Different styles

• Intro Camera– Introduces you to the stage and actors – Starts at a distance and then moves toward

the subject– When it get to the subject circle around the

subject– Only used at the beginning when everything is

stationary

First person camera

• Presents the stage from the subject’s point of view

• Useful in racing games • Important to have a frame of reference on

the subject• Can be used often but for only short

periods of time

Follow or Third-person camera

• Shows part of the scene and the subject from behind

• Many variations of this camera from different heights and distances

• Used as a calming section after an action sequence

• This camera can be used for up to 50% of the replay

Matrix camera

• Pauses some or all the action and then circles around the subject

• This gives a very dramatic effect

• Should be used when something spectacular is happening

• Use this camera very sparingly

Circle camera

• Slowly circles the subject while looking at them

• Good for a slow portion of the replay

• Can be used as a transition from side to side of the player

Still frame camera

• As the subject passes, the action is paused at regular intervals simulating photographs

• Used in conjunction with photographers on the sidelines

Camera switching rules

• Don’t cut to the opposite side of a player it is disorienting

• Subject should always be in sight• Transitions from camera to camera should

be fluid • Special cameras (matrix) should be used

sparingly

Camera Switching rules cont…

• Use follow cameras a lot to serve as breathers between other cameras

• All cameras should know where to switch to in case they lose sight of the subject

• Make sure the camera types used are appropriate for the game type

Some good tools

• Switching the subject of each camera • Taking screen shots • Stop subject while the rest of the scene

continues • See and change what camera the current

camera is going to switch to• Tools to allow an artist or designer to fine

tune the replays

Freak Out - Extreme Freeride

• Snow boarding sports replay

• Shows examples of the different kinds of cameras

• http://www.youtube.com/watch?v=Axwy2j2E84M

Super Mario Galaxy

• Good camera implementation

• A lot of open field areas without many obstacles

• www.youtube.com/watch?v=v7bN-YhEEtI

Legend of Zelda: ocarina of time

• Boss battle with terrible camera implementation

• http://www.youtube.com/watch?v=ef4z7SQi5Oc