Package edu.cornell.gdiac.graphics

Class Stencil

java.lang.Object

edu.cornell.gdiac.graphics.Stencil

public class Stencil
extends Object

A class to support stenciling effects.

A SpriteBatch can support many types of stencil effects. Classic stencil effects including clipping (limiting drawing to a specific region) or masking (prohibiting drawing to a specific region).

In particular, stencil effects are designed to support simple constructive area geometry operations. You can union, intersect, or subtract stencil regions to produce the relevant effects. However, this is only used for drawing and does not actually construct the associated geometries.

To support the CAG operations, the sprite batch stencil buffer has two areas: low and high. Operations can be applied to one or both of these regions. All binary operations are operations between these two regions. For example, Stencil.Effect.CLIP_MASK will restrict all drawing to the stencil region defined in the low buffer, while also prohibiting any drawing to the stencil region in the high buffer. This has the visible effect of "subtracting" the high buffer from the low buffer.

The CAG operations are only supported at the binary level, as we only have two halves of the stencil buffer. However, using non-drawing effects like Stencil.Effect.CLIP_WIPE or Stencil.Effect.CLIP_CARVE, it is possible to produce more interesting nested expressions.

Note that when using split-buffer operations, only one of the operations will modify the stencil buffer. That is why there no effects such as FILL_WIPE or CLAMP_STAMP.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	Stencil.Effect	An enum enumerating all of the supported stencil effects.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	STENCIL_BOTH	Both buffers
static final int	STENCIL_LOWER	Lower buffer
static final int	STENCIL_NONE	Neither stencil effect buffer
static final int	STENCIL_UPPER	Upper buffer

Constructor Summary

Constructors

Constructor	Description
Stencil()

Method Summary

Modifier and Type	Method	Description
static void	applyEffect(Stencil.Effect effect)	Configures the OpenGL settings to apply the given effect.
static void	clearBuffer(int buffer)	Clears the stencil buffer specified

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

STENCIL_NONE

public static final int STENCIL_NONE

Neither stencil effect buffer

See Also:

• Constant Field Values

STENCIL_LOWER

public static final int STENCIL_LOWER

Lower buffer

See Also:

• Constant Field Values

STENCIL_UPPER

public static final int STENCIL_UPPER

Upper buffer

See Also:

• Constant Field Values

STENCIL_BOTH

public static final int STENCIL_BOTH

Both buffers

See Also:

• Constant Field Values

Constructor Details

Stencil

public Stencil()

Method Details

clearBuffer

public static void clearBuffer(int buffer)

Clears the stencil buffer specified

Parameters:

buffer - The stencil buffer (lower, upper, both)

applyEffect

public static void applyEffect(Stencil.Effect effect)

Configures the OpenGL settings to apply the given effect.

Parameters:

effect - The stencil effect