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workshop08_sceneManagement.adoc

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Scene Management

Where we want to get to

  • Have all our sprites in some kind of collection

  • Be able to render our sprites from that collection

  • Be able to add/remove sprites from that collection

  • Make sure that sprites are deallocated appropriately

  • Make sure we aren’t allocating/deallocating when we don’t need to

  • Make other ways of "indexing"/finding out sprites

Where you should already be

  • Have a working build system, that uses SDL

  • Create a window, change its size, including fullscreen

  • Have a program that draws a sprite on the screen

    • with a size and position that you can control/change

    • sprite position and size independent of window resolution

  • Compensate for real-time in your Game Loop

  • Have a sprite class to encapsulate sprite data

  • Have a container to store multiple sprites

  • Be able to update and render multiple sprites

Activity summary

  • We’ll be adding stuff to main.cpp to do more interesting things

  • You could continue with your existing code (take a snapshot/commit)

    • or start a fresh project

Use a container to store your sprites

  • Make your code use a standard container to store your sprites

    • this was in a previous week’s workshop, so you may already have this

  • Which kind of container would make most sense?

    • What do you need from the container?

Render the container of sprites

  • Make your code render the sprites that are in the collection

Make sprites update

  • Make your code (continue to) update your sprites position

    • i.e. they should move automatically, according to a velocity

    • if your code is presently dependent on "key-repeat" now it a VERY GOOD time to remove this dependency

      • a sprite that initially has upwards velocity should move upwards automatically, without any key-presses

Add a new sprite to the container on a key-press

  • Make your code add a new sprite to the container on a key-press

    • with a random velocity

Remove a sprite on a key-press

  1. Remove your first-created sprite on a key-press

  2. Remove the last-created sprite on a key-press

  3. Remove a random sprite on a key-press

  4. Manage the case of when there are no sprites left

    • i.e. if you just keeping hitting the remove sprite key

Make sure that sprites are deallocated appropriately

  1. Add logging to the sprite class to log when the sprite is deallocated

  2. Check that when you remove a sprite a sprite is deallocated

  3. Check that when your program exits all the sprites are deallocated

Make sure we aren’t allocating/deallocating when we don’t need to

  1. Add logging to the sprite class to log when the sprite is allocated or copied

    • see lecture notes

  2. Make sure that at initialisation time, only the required number of allocations occur

    • copies are ok

  3. Try to eliminate the copying at initialisation time (within a sensible limit)

  4. Make sure that during your game loop, only the required number of allocations occur

    • ideally zero, except when you create new sprites

    • What is a copy constructor? And how/when is it called?

Think about other ways of "indexing"/finding out sprites

  • Finding sprites in our container is presently quite hard

  • Perhaps we want to be able to find a sprite by a name (std::string)

    • There are a number of ways of doing this

      1. Discuss with a friend or demonstrator about two different ways you can come up with

Make other ways of "indexing"/finding out sprites

  • Which standard container would be helpful here?

  • How is this container declared?

  • How are elements added to this container

  • How do your iterate elements in this container?

    1. Modify your code to use your chosen container instead of std::vector