What is alpha value in glClearColor?
What is alpha value in glClearColor?
glClearColor sets the color (and alpha value) a RGBA framebuffer will be cleared to with glClear(GL_COLOR_BUFFER_BIT) . The framebuffer alpha value would be taken into account with GL_DST_ALPHA or GL_ONE_MINUS_DST_ALPHA blend functions.
What is alpha in OpenGL?
The amount of transparency of an object is defined by its color’s alpha value. The alpha color value is the 4th component of a color vector that you’ve probably seen quite often now. Up until this chapter, we’ve always kept this 4th component at a value of 1.0 giving the object 0.0 transparency.
How does OpenGL implement transparency?
OpenGL “transparency” would instead blend the RGB of the red object with the RGB of the green glass, giving a shade of yellow. Instead of using glColor3f( ) to specify the red, green, and blue of an object, use glColor4f( ) to specify red, green, blue, and alpha. Alpha is the transparency factor.
What is an alpha background?
In computer graphics, alpha compositing or alpha blending is the process of combining one image with a background to create the appearance of partial or full transparency. Alpha blending is also used in 2D computer graphics to put rasterized foreground elements over a background.
What is glClear?
The glClear function takes a single argument (mask) that is the bitwise OR of several values indicating which buffer is to be cleared. The value to which each buffer is cleared depends on the setting of the clear value for that buffer. If a buffer is not present, a glClear call directed at that buffer has no effect.
What is difference between glClearColor and glClear function?
glClear actually clears the buffer, while glClearColor just sets the colour to clear the buffer to. glClear is a Command: which clears the buffer. glClearColor is State Setting: which sets the color value to buffer.
What is blending and rendering?
Blending is the stage of OpenGL rendering pipeline that takes the fragment color outputs from the Fragment Shader and combines them with the colors in the color buffers that these outputs map to. Blending parameters can allow the source and destination colors for each output to be combined in various ways.
What is glViewport?
The glViewport function specifies the affine transformation of x and y from normalized device coordinates to window coordinates.
Is it possible to achieve with glblendfunc and alpha channel?
Basically I want the following equation: Is this possible to achieve using glBlendFunc or do I have to resort to shaders and multiple FBOs for read-back? Does the blend func you want. Just draw your opaque square, then check the alpha channel.
How to enable and disable blending in glblendfunc?
Use glEnable and glDisable with argument GL_BLEND to enable and disable blending. glBlendFunc defines the operation of blending when it is enabled. sfactor specifies which method is used to scale the source color components. dfactor specifies which method is used to scale the destination color components.
What is the function of glblendfunc in Win32?
When enabled, glBlendFunc defines the operation of blending. The sfactor parameter specifies which of nine methods is used to scale the source color components. The dfactor parameter specifies which of eight methods is used to scale the destination color components. The eleven possible methods are described in the following table.
What is the initial value of glblendfunci in OpenGL?
For glBlendFunci, specifies the index of the draw buffer for which to set the blend function. Specifies how the red, green, blue, and alpha source blending factors are computed. The initial value is GL_ONE . Specifies how the red, green, blue, and alpha destination blending factors are computed.