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Cameras.md

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Cameras

Vulkan2D has fairly simple but powerful 2D camera features that you can use in many scenarios.

Creating Cameras

Cameras may be created with vk2dCameraCreate. You must provide a camera spec to create the camera which is information on where the camera is in the game world and how its orientated. The spec also contains info on where the camera is drawn on the screen in the form of the struct members xOnScreen, yOnScreen, wOnScreen, and hOnScreen. xOnScreen and yOnScreen specify where the camera is to be drawn on the game window and wOnScreen and hOnScreen specify the width and height of the camera in the window. This can be used to make a split-screen effect, where you have 4 cameras, each specifying 1/4 of the game window but with different x/y offsets in the window. vk2dCameraCreate returns a VK2DCameraIndex which the you will need to store if you wish to update the camera at a later time. If vk2dCameraCreate returns VK2D_INVALID_CAMERA then there are no more available camera spots - the total number of cameras that can exist at once can be changed in the file VK2D/Constants.h.

Updating Cameras

Using the VK2DCameraIndex acquired from vk2dCameraCreate you can call vk2dCameraUpdate to update the spec of a given camera. vk2dCameraUpdate may be called at any time but the camera matrix is built when vk2dRendererStartFrame is called and any calls to update a camera's spec after that will not be applied until the next frame starts. You may also use vk2dCameraSetState to update a camera's state to one of the following:

  • VK2D_CAMERA_STATE_NORMAL Camera is drawn to as you would expect
  • VK2D_CAMERA_STATE_DISABLED Camera still exists, but it will not be drawn to
  • VK2D_CAMERA_STATE_DELETED Camera will be deleted and the corresponding VK2DCameraIndex is now invalid
  • VK2D_CAMERA_STATE_RESET For internal use only, do not use

Unlike updating a camera's spec, updating the state is applied immediately and you can enable/disable cameras mid frame all you like - but locking cameras may be what you want.

The Default Camera

By default, the renderer creates and manages one camera which is accessible via the constant VK2D_DEFAULT_CAMERA. This camera isn't really meant to be used for the game world but it can be updated and changed like any camera. Although you may update the default camera via VK2D_DEFAULT_CAMERA or using the renderer's camera functions (which are just wrappers for Camera.h functions) the renderer will automatically set the wOnScreen/hOnScreen of the default camera's spec to the window width/height whenever the window size is changed. The renderer does not touch the spec of user created cameras automatically. For this reason it is recommended you use the default camera for UI elements and create your own camera for the game world and use camera locking to isolate the two (the demo in main.c does exactly that).

Locking Cameras

Normally all cameras are drawn to every time you draw something, which is useful for split screen. Should you want to draw certain elements of the game to only particular cameras you can either disable the cameras you don't want to draw to or just lock the renderer to a single camera. Using vk2dRendererLockCameras you can specify a single camera that will be drawn to and all others will be ignored. Call vk2dRendererUnlockCameras to revert the renderer back to drawing like normal.