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PAGE [Cocos3.8 Tutorial] RenderTexture + Blur This tutorial will help you to understand how you can use shaders and render textures in cocos2d-x 3.0 and will give you some insights in the underlying math. In one of my projects I faced a necessity to make a blurred version of some background landscape, which composition depends on the screen size, that is clouds are sticked to the top of the screen and ground is sticked to the bottom, so its not an option to just put a blurred image in the resource folder. The landscape must be composed, drawn in a RenderTexture, then drawn again with blurring shader, saved to disk and used in consequent launches. The image can be pretty big and the blur radius can be pretty big as well, so we need something fast. This tutorial can be divided into following steps:1. Diving into math and calculating gaussian weights2. Creating blur shader3. Rendering texture and saving it to file4. Using TextureBlur in a sample program Lets start. To blur a pixel we just need to calculate a weighted sum of the surrounding pixels, where weights themselves sum up to 1. Another property that would be nice to have is that central weights must be heavier than the side ones. Why Gaussian function is usually picked for making blur effect? Because it has three nice features:1. Its integral equals 12. Its maximum value is in the symmetry point3. It has the following feature: Tow-dimensional Gaussian function can be split into a product of two one-dimensional functions. What it will give us? To calculate the color of the blurred pixel with coordinate (i, j) in a straightforward manner we need to sum up all the pixels in range (i-R, i+R)x(j-R, j+R), where R is a blur radius. This results in a nested loop and nested loop means O(n*n) complexity and we really do not want such a thing in a shader. Keeping in mind the 3rd feature of the Gaussian distribution we can split the nested loop in two consequent loops. At first we will do a horizontal blur and then