Gl_FragColor.r = (gl_FragColor.r * alpha +leftColor.r + rightColor.r + upColor.r + downColor.r) * rBeta Vec4 downColor = texture2D(x,vec2(pixel.x,pixel.y+yPixel)) Vec4 upColor = texture2D(x,vec2(pixel.x,pixel.y-yPixel)) Vec4 rightColor = texture2D(x,vec2(pixel.x+xPixel,pixel.y)) Vec4 leftColor = texture2D(x,vec2(pixel.x-xPixel,pixel.y)) X = gl_FragCoord.x - dxt0 * (texture2D(velocity, pixel).x ) Uniform sampler2D quantity //quantity to advect Uniform sampler2D velocity //input velocity Uniform vec2 res //The width and height of our screen Here are the shaders I am using: //advection Instead of posting all of my code, the general process I follow is:įor diffusing velocity and computing pressure I am only do 10 iterations because thats all my computer can handle with my implementation (I will optimize once I get it working), but I feel like the computing pressure and subtracting gradient are not having any effect. I can supply any pictures/links to the simulation if that would help.Īfter some more investigation I believe the problem is related to my advection function. I know the code I am posting is al little confusing due to the nature of what it is about. I calculate pressure using the diffusion shader as described in the linked resource. I displayed the divergence and I get very little around where I am moving the object around as well as when the velocity hits the edge (boundary), but the pressure that I get is completely empty. I added boundaries but it seems like they are having no effect, which makes me suspicious about how much pressure and advection are working. I have implemented everything but I feel like there are multiple things that aren't working correctly. Gl_FragColor = vec4(coord.x/800.0,coord.y/600.0, 0.0, 1.I am trying to get a fluid simulation to work using WebGL using as a resource. This one sets the color of each pixel based on its coordinates. This is the vertex shader we’ll make no changes on the vertices and will simply let the data pass through it: Īnd this is the fragment shader. This is the heart of our WebGL application.įirst we’ll create our shaders. Their jobs are to return coordinates and colors, respectively. Shaders are functions: a vertex shader will be run once per vertex, and the fragment shader is called once per pixel. Then we’ll need a program, which is comprised of a vertex shader and a fragment shader. Var canvas = document.getElementById("container") canvas id="container" width="800" height="600">canvas> WebGL renders on canvas, and it is a rendering context like the one we get with canvas.getContext('2d'). The first thing we need is a canvas element. In this article we will only show a basic example of how to use it for a more in depth explanation, check out the excellent WebGl Fundamentals page. It is based on OpenGL ES, and the shaders aren’t written in JS at all, but rather in a language called GLSL.Īll in all, that makes it look difficult to use if you’re coming from exclusively web development - it’s not only a new language, but new concepts as well - but once you grasp some key concepts it will become much easier. WebGL is a JavaScript API for rendering 2D and 3D graphics, allowing the use of the GPU for better performance. To simulate this behavior, we’ll have to render a lot of drops, and update the refraction on them on every frame, and do all this with a decent frame rate, we’ll need a pretty good performance – so, to be able to use hardware accelerated graphics, we’ll use WebGL. You’ll also see that drops that are close to each other get merged – and if it gets past a certain size, it falls down, leaving a small trail. Image credits: Wikipedia, GGB reflection in raindrop If you look up pictures of water drops on a window in detail (or, of course, observed them in real life already), you will notice that, due to refraction, the raindrops appear to turn the image behind them upside down. If we want to make an effect based on the real world, the first step is to dissect how it actually looks, so we can make it look convincing. Please note that the effect is highly experimental and might not work as expected in all browsers.
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