These qualifiers help the shader understand the purpose and scope of each variable.Īttribute: Variables passed in by OpenGL to the vertex shader. If you have created a shader in GameMaker Studio 2, you might have noticed these words in the default pass-through shader. Variable qualifiers in shaders: attribute, varying, and uniform Here is where we get information about our textures and can tweak the final color of each pixel in our image. Fragment shaders are much more interesting and are what will be covered mostly in this article. They become much more useful in 3D for lighting calculations and mesh deformations. These shaders are not particularly useful in 2D, since every sprite is usually a square, but can be used to do some skewing, scaling, etc. It is used to calculate positions, normals, and texture coordinates. The vertex shader is executed first, and as the name implies, it deals with vertices. The math and techniques should be similar between all three languages, save for a few syntax differences here and there. In this tutorial, I will use GLSL ES as my shader language since it’s the one that provides the best portability across systems. GameMaker Studio 2 allows users to write shaders in GLSL (OpenGL Shader Language), HLSL (High-level Shader Language, used when working with DirectX), and GLSL ES (a subset of GLSL which is common in mobile devices). The limitation is that we only have access to the initial state of the sprite, so we don’t know about any modifications done to other pixels since we can’t know for sure the code has run on them yet. This is helpful for shaders because we can execute the shader code of thousands of pixels concurrently. In contrast, modern GPUs can perform thousands, and even tens of thousands, of tasks running at the same time. Modern CPUs typically have between two to eight cores. Each core can perform one task at a time, so by taking advantage of multiple cores, we can perform that many tasks simultaneously. The reason shader code is usually executed by the GPU is that it is more efficient at it. For example, if you want a shader to make your sprite be black and white, then you’d calculate which shade of grey each pixel needs to be to create the effect. In your fragment shader code, you perform operations and calculations to determine the color of that pixel to get the effect you want. This allows us to change the vertex position and color before passing it over to the fragment shader since the vertex shader is executed earlier.įor the fragment shader, you can imagine the same loop as before, but this time it goes over every single pixel in your sprite, giving you information such as location and color of that pixel. Now, imagine we have a for loop that goes over every vertex and executes the code inside the vertex shader for each. This leaves us with six vertices per sprite, but two of those are the same one, so we should only worry about four. Each sprite is formed by a rectangle, but computers like to draw triangles, so those rectangles are split into two triangles. However, I came up with an analogy that made it much simpler for me to think about them. When I first started learning about shaders, I had a tough time getting my head around how they work. This difference comes with its own set of rules and limitations, but we’ll cover those later.Įach shader is made up of two separate scripts: a vertex shader and a fragment shader (also referred to as pixel shader). Shader code is similar to regular code, but it is (almost always) executed by the GPU (your graphics card), not the CPU (your processor). Initially created to provide shading for lighting (hence the name), they are now used to produce a huge variety of effects. To follow along, you do not need any previous knowledge of these features, but it is necessary that you have a basic understanding of programming and know your way around GameMaker Studio 2. They are also among the most advanced features offered by GameMaker Studio 2, but I will try to explain everything as simply as possible in this post. Shaders are often used to create beautiful graphical effects in games.
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