fragment-shader

A parallax background with a fixed camera is easy to do, but since i'm making a topdown view 2D space exploration game, I figured that having a single SKSpriteNode filling the screen and being a child of my SKCameraNode and using a SKShader to draw a parallax starfield would be easier. I went on shadertoy and found this simple looking shader. I adapted it successfully on shadertoy to accept a vec2() for the velocity of the movement that I want to pass as an SKAttribute so it can follow the movement of my ship. Here is the original source: https://www.shadertoy.com/view/XtjSDh I managed to make

Short: Can I define a function that every shader can use? Or I have to define it per shader? The whole story: I want to create numerous shaders intended to colorize the input fragments with predefined gradient ramps (something like this - http://www.thinkboxsoftware.com/storage/krakatoa-support-images/krakatoa15_kcm_densitybyage_gradientrampmap.png ). I want to define a gradient ramp constant for each shader (an array of vec4 color samples, where the alpha value holds the gradient position, see Pos in the picture above) And I need a function that can return a color sample from the given

I've implemented a gaussian blur fragment shader in GLSL. I understand the main concepts behind all of it: convolution, separation of x and y using linearity, multiple passes to increase radius... I still have a few questions though: What's the relationship between sigma and radius? I've read that sigma is equivalent to radius, I don't see how sigma is expressed in pixels. Or is "radius" just a name for sigma, not related to pixels? How do I choose sigma? Considering I use multiple passes to increase sigma, how do I choose a good sigma to obtain the sigma I want at any given pass? If the

I'm just looking to create a very simple Fragment Shader that draws a specified texture to the mesh. I've looked at a handful of custom fragment shaders that accomplished the same and built my own shaders and supporting JS code around it. However, it's just not working. Here's a working abstraction of the code I'm trying to run: Vertex Shader <script id="vertexShader" type="x-shader/x-vertex"> varying vec2 vUv; void main() { vUv = uv; gl_Position = projectionMatrix * modelViewMatrix * vec4(position,1.0); } </script> Fragment Shader <script id="fragmentShader" type="x-shader/x-fragment">