Blending Class Reference

#include <ImFusion/Core/GL/Blending.h>

Helper class to configure the OpenGL blending stage. More...

Inheritance diagram for Blending:

Detailed Description

Helper class to configure the OpenGL blending stage.

The OpenGL blending stage defines how a new pixel ("source") is combined with an already existing pixel in the framebuffer ("destination") in order to yield the final pixel value. OpenGL splits this configuration in multiple parts:

• The blending Equation defines the mathematical function how source and destination are combined.
• The blending Function allows to define how each the source and destination components are derived from the input data. If you choose a constant color/alpha value as input that value is specified through setBlendColor().

Warning

This class modifies global OpenGL state! Therefore, it implements state guard semantics, which means that it restores the original blending state on destruction of its instance.

Usage Example:

{
    // render a quad with alpha blending
    GL::Blending blendingGuard(GL::Blending::Preset::AlphaBlending);
    renderQuad();
 
    // disable blending and render a triangle on top
    blendingGuard.setBlendingEnabled(false);
    renderTriangle();
 
} // leaving the scope will destroy the blending guard and restore the original OpenGL blending state

See also

https://www.khronos.org/opengl/wiki/Blending

Public Types
enum class	Preset { Disabled , AlphaBlending }
	Enumeration of commonly used blending modes. More...
enum class	Equation {   FuncAdd = 0x8006 , FuncSubstract = 0x800A , FuncReverseSubstract = 0x800B , Min = 0x8007 ,   Max = 0x8008 }
	Enumeration to define how source and destination blending component are combined to yield the output pixel value. More...
enum class	Function {   Zero = 0 , One = 1 , SrcColor = 0x0300 , OneMinusSrcColor = 0x0301 ,   SrcAlpha = 0x0302 , OneMinusSrcAlpha = 0x0303 , DstColor = 0x0306 , OneMinusDstColor = 0x0307 ,   DstAlpha = 0x0304 , OneMinusDstAlpha = 0x0305 , ConstantColor = 0x8001 , OneMinusConstantColor = 0x8002 ,   ConstantAlpha = 0x8003 , OneMinusConstantAlpha = 0x8004 }
	Enumeration to define how a blending component (source/destination) should be computed. More...

Public Member Functions
	Blending (Preset preset)
	Sets up OpenGL blending based on the given preset.
	Blending (Function sourceFunc, Function destinationFunc)
	Enables OpenGL blending and sets the blend function as defined.
	Blending (Function sourceFuncRGB, Function destinationFuncRGB, Function sourceAlpha, Function destinationAlpha)
	Enables OpenGL blending and sets the blend function as defined.
	Blending (Blending &&rhs) noexcept
Blending &	operator= (Blending &&rhs) noexcept
	~Blending ()
	Restores the original OpenGL blending state of when this instance was created.
void	setBlendingEnabled (bool isEnabled)
	Enables or disables the OpenGL blending stage.
void	setPreset (Preset preset)
	Sets up OpenGL blending based on the given preset.
void	setFunction (Function sourceFunc, Function destinationFunc)
	Defines the arithmetic how source and destination blending factors are computed uniformly for all RGBA channels.
void	setFunction (Function sourceFuncRGB, Function destinationFuncRGB, Function sourceAlpha, Function destinationAlpha)
	Defines the arithmetic how source and destination blending factors are computed and allows for different functions for color and alpha channels.
void	setEquation (Equation blendEquation)
	Defines how the new pixel is combined with the pixel already in the framebuffer, uniformly for all RGBA channels.
void	setEquation (Equation blendEquationRGB, Equation blendEquationAlpha)
	Defines how the new pixel is combined with the pixel already in the framebuffer, allowing for different equations for color and alpha channels.
void	setBlendColor (vec4f blendColor)
	Defines the reference color used when choosing one of the Constant blend functions.

Member Enumeration Documentation

Preset

enum class Preset

strong

Enumeration of commonly used blending modes.

Enumerator
Disabled	Disables blending, new pixels will completely replace/overwrite existing pixels.
AlphaBlending	Enables blending and sets (Function::SrcAlpha, Function::OneMinusSrcAlpha, Function::One, Function::OneMinusSrcAlpha) as blend function.

Equation

enum class Equation

strong

Enumeration to define how source and destination blending component are combined to yield the output pixel value.

See also

https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBlendEquationSeparate.xhtml

Enumerator
FuncAdd	The source and destination colors are added to each other.
FuncSubstract	Subtracts the destination from the source.
FuncReverseSubstract	Subtracts the source from the destination.
Min	The output color is the component-wise minimum value of the source and dest colors.
Max	The output color is the component-wise maximum value of the source and dest colors.

Function

enum class Function

strong

Enumeration to define how a blending component (source/destination) should be computed.

See also

https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBlendFuncSeparate.xhtml

Enumerator
Zero	Use all zeros as blending input.
One	Use all ones as blending input.
SrcColor	Use the source color as input.
OneMinusSrcColor	Use (1 - source color) as input.
SrcAlpha	Use the source alpha value as input.
OneMinusSrcAlpha	Use (1 - source alpha) as input.
DstColor	Use the destination color as input.
OneMinusDstColor	Use (1 - destination color) as input.
DstAlpha	Use the destination alpha as input.
OneMinusDstAlpha	Use (1 - destination alpha) as input.
ConstantColor	Use the blending color as input.
OneMinusConstantColor	Use (1 - blend color) as input.
ConstantAlpha	Use the blending color's alpha value as input.
OneMinusConstantAlpha	Use (1 - blend color alpha) as input.

---

The documentation for this class was generated from the following file:

• ImFusion/Core/GL/Blending.h