What is the purpose of blending in OpenGL?
Blending in OpenGL is commonly known as the technique to implement transparency within objects. Transparency is all about objects (or parts of them) not having a solid color, but having a combination of colors from the object itself and any other object behind it with varying intensity.
Which is the best way to learn OpenGL?
Learning (and using) modern OpenGL requires a strong knowledge of graphics programming and how OpenGL operates under the hood to really get the best of your experience. So we will start by discussing core graphics aspects, how OpenGL actually draws pixels to your screen, and how we can leverage that knowledge to create some funky looking effects.
What should the blending factor be in fragment shader?
Ensure the fog factor is in the range 0 (no fog) to 1 (max fog) In the fragment shader, we could have code like follows: The fog blending factor is usually a simple equation, which could be one of the following, where d is the density of the fog.
When to use RGB or RGBA in blending?
When blending is enabled, the colour of surfaces can be combined, if the surface in front is not completely opaque. This can be calculated using the alpha value of the colour. Instead of RGB, we can use RGBA, where the A is the opacity of the colour, ranging from 0 (transparent) to 1 (opaque).
How does scalar multiplies against colors work in OpenGL?
Scalar multiplies against colors are also component-wise multiplies. The source color S output from the fragment shader will be clamped to [0, 1] if the image format of the destination buffer that it is destined for is a normalized integer format. Otherwise, it will be used as given.
Can a fragment shader change the blend color?
The blend color is a state value, like the blend equations and blend parameters. Therefore, it cannot change within a single draw call; fragment shaders cannot write to, modify, or even access the blend color. All buffers share the same blend color.
When do you use transparent texels in OpenGL?
If you want to draw something complicated like a tree, you probably can’t afford a polygon for every single leaf and branch; so you use an texture that has pictures of leaves. In this case, the leaf texture has no translucent texels; either the texel is opaque or it is completely transparent.
Why is there no floating point equality test in OpenGL?
So if there is any kind of GL_LINEAR filtering, the values you get will not always be 1.0 and 0.0, even if those are the alpha values in the texture. That’s why the test is set to be less than 0.5. It would not be a good idea to do a floating-point equality test, like { { {1}}} .
How to make parts of a texture transparent?
For your testing purposes, create texture from buffer like this (this is D source, you should be able to convert it to C++ quite easily): Using this texture, when everything works well, you should be able to create arbitrary sized rectangles on screen. Change alpha values to see that blending works.