fragment-shader

This question already has an answer here: What are Vertex and Pixel shaders? 5 answers I've read some tutorials regarding Cg, yet one thing is not quite clear to me. What exactly is the difference between vertex and fragment shaders? And for what situations is one better suited than the other? The Surrican A fragment shader is the same as pixel shader. One main difference is that a vertex shader can manipulate the attributes of vertices. which are the corner points of your polygons. The fragment shader on the other hand takes care of how the pixels between the vertices look. They are

I would like to use some 3D textures for objects that I'm rendering in WebGL. I'm currently using the following method in a fragment shader, as suggested on WebGL and OpenGL Differences : // tex is a texture with each slice of the cube placed horizontally across the texture. // texCoord is a 3d texture coord // size is the size if the cube in pixels. vec4 sampleAs3DTexture(sampler2D tex, vec3 texCoord, float size) { float sliceSize = 1.0 / size; // space of 1 slice float slicePixelSize = sliceSize / size; // space of 1 pixel float sliceInnerSize = slicePixelSize * (size - 1.0); // space of

I want to access the depth buffer value at the currently processed pixel in a pixel shader. How can we achieve this goal? Basically, there seems to be two options: Render depth to texture. How can we do this and what is the tradeoff? Use the value provided by gl_FragCoord.z - But: Is this the correct value? On question 1: You can't directly read from the depth buffer in the fragment shader (unless there are recent extensions I'm not familiar with). You need to render to a Frame Buffer Object (FBO). Typical steps: Create and bind an FBO. Look up calls like glGenFramebuffers and

In the learningwebgl tutorial1 I've found an interesting line in the fragment shader. precision mediump float; I've found an article about it here , but I still can't understand what does it mean? And if I remove this line, nothing changes. Everything is the same. So what does precision mediump float mean? HowDoIDoComputer This determines how much precision the GPU uses when calculating floats. highp is high precision, and of course more intensive than mediump (medium precision) and lowp (low precision). Some systems do not support highp at all, which will cause code not to work at all on

I have some simple polygons (fewer than 20 vertices) rendering flat on a simple xy plane, using GL_TRIANGLES and a flat color, a 2d simulation. I would like to add a border of variable thickness and a different color to these polygons. I have something implemented using the same vertices and glLineWidth/GL_LINE_LOOP, which works, but is another rendering pass and repeats all the vertex transforms. I think I should be able to do this in the fragment shader using gl_FragCoord and the vertex data and/or texture coordinates, but I'm not sure, and my naive attempts have been obviously incorrect. I

My task is to render quadratic Bezier curve (path) via Stage3d (Adobe Flash) technology, which have no any extensions for that drawing out-of-the box (while OpenGl have it, as I know). Yea, there is a Starling-Extension-Graphics, but it uses simple method to divide a curve segment to many straight lines, that generates very many triangles for my long curve path. So.. There is a perfect way for rendering resolution independed shapes for Loop and Blinn. I've read GPUGems3 article (gpugems3_ch25.html) and ported that fragment shader to AGAL2: Quadratic Curve Pixel Shader float4 QuadraticPS(float2