Package com.badlogic.gdx.graphics.g3d

Interface Shader

All Superinterfaces:

Disposable

All Known Implementing Classes:

BaseShader, DefaultShader, DepthShader, ParticleShader

public interface Shader
extends Disposable

Interface which is used to render one or more Renderables.

A Shader is responsible for the actual rendering of an Renderable. Typically, when using OpenGL ES 2.0 or higher, it encapsulates a ShaderProgram and takes care of all OpenGL calls necessary to render the Renderable. When using OpenGL ES 1.x it takes care of the fixed pipeline.

To start rendering the begin(Camera, RenderContext) method must be called. After which the end() method must be called to stop rendering. In between one or more calls to the render(Renderable) method can be made to render a Renderable. The render(Renderable) method must not be called before a call to begin(Camera, RenderContext) or after a call to end(). Each Shader needs exclusive access to the OpenGL state and RenderContext between the begin(Camera, RenderContext) and end() methods, therefore only one shader can be used at a time (they must not be nested).

A specific Shader instance might be (and usually is) dedicated to a specific type of Renderable. For example it might use a ShaderProgram that is compiled with uniforms (shader input) for specific Attribute types. Therefore the canRender(Renderable) method can be used to check if the Shader instance can be used for a specific Renderable. Rendering a Renderable using a Shader for which canRender(Renderable) returns false might result in unpredicted behavior or crash the application.

To manage multiple shaders and create a new shader when required, a ShaderProvider can be used. Therefore, in practice, a specific Shader implementation is usually accompanied by a specific ShaderProvider implementation (usually extending BaseShaderProvider).

When a Shader is constructed, the init() method must be called before it can be used. Most commonly, the init() method compiles the ShaderProgram, fetches uniform locations and performs other preparations for usage of the Shader. When the shader is no longer needed, it must disposed using the Disposable.dispose() method. This, for example, disposed (unloads for memory) the used ShaderProgram.

Method Summary

Modifier and Type	Method	Description
void	begin(Camera camera, RenderContext context)	Initializes the context for exclusive rendering by this shader.
boolean	canRender(Renderable instance)	Checks whether this shader is intended to render the Renderable.
int	compareTo(Shader other)	Compare this shader against the other, used for sorting, light weight shaders are rendered first.
void	end()	Cleanup the context so other shaders can render.
void	init()	Initializes the Shader, must be called before the Shader can be used.
void	render(Renderable renderable)	Renders the Renderable, must be called between begin(Camera, RenderContext) and end().

Methods inherited from interface com.badlogic.gdx.utils.Disposable

dispose

Method Detail

init

void init()

Initializes the Shader, must be called before the Shader can be used. This typically compiles a ShaderProgram, fetches uniform locations and performs other preparations for usage of the Shader.

compareTo

int compareTo(Shader other)

Compare this shader against the other, used for sorting, light weight shaders are rendered first.

canRender

boolean canRender(Renderable instance)

Checks whether this shader is intended to render the Renderable. Use this to make sure a call to the render(Renderable) method will succeed. This is expected to be a fast, non-blocking method. Note that this method will only return true if it is intended to be used. Even when it returns false the Shader might still be capable of rendering, but it's not preferred to do so.

Parameters:

instance - The renderable to check against this shader.

Returns:

true if this shader is intended to render the Renderable, false otherwise.

begin

void begin(Camera camera,
           RenderContext context)

Initializes the context for exclusive rendering by this shader. Use the render(Renderable) method to render a Renderable. When done rendering the end() method must be called.

Parameters:

camera - The camera to use when rendering

context - The context to be used, which must be exclusive available for the shader until the call to the end() method.

render

void render(Renderable renderable)

Renders the Renderable, must be called between begin(Camera, RenderContext) and end(). The Shader instance might not be able to render every type of Renderables. Use the canRender(Renderable) method to check if the Shader is capable of rendering a specific Renderable.

Parameters:

renderable - The renderable to render, all required fields (e.g. Renderable.material and others) must be set. The Renderable.shader field will be ignored.

end

void end()

Cleanup the context so other shaders can render. Must be called when done rendering using the render(Renderable) method, which must be preceded by a call to begin(Camera, RenderContext). After a call to this method an call to the render(Renderable) method will fail until the begin(Camera, RenderContext) is called.