Vertex shader vs Fragment Shader

opengl cg fragment-shader vertex-shader
adivasile picture adivasile · Dec 12, 2010 · Viewed 86.1k times · Source

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?

Answer

The Surrican picture The Surrican · Dec 12, 2010

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 interpolated between the defined vertices following specific rules.

For example: if you want your polygon to be completely red, you would define all vertices red. If you want for specific effects like a gradient between the vertices, you have to do that in the fragment shader.

Put another way:

The vertex shader is part of the early steps in the graphic pipeline, somewhere between model coordinate transformation and polygon clipping I think. At that point, nothing is really done yet.

However, the fragment/pixel shader is part of the rasterization step, where the image is calculated and the pixels between the vertices are filled in or "coloured".

Just read about the graphics pipeline here and everything will reveal itself: http://en.wikipedia.org/wiki/Graphics_pipeline

Related questions

how to set a boolean property in unity3d CGprogram shader?

I am writing a shader for unity3d and I want to specify the properties of the shader in i.e like - Shader "GraphicsQuality/MediumScan" { Properties { _Color ("Main Color", Color) = (1,1,1,1) _SpecColor ("Specular Color", Color) = (0.5,0.5,0.5,1) _Shininess ("Shininess", Range (0.01, 1)) = 0.078125 _MainTex ("Base (…

Read More
what are passes and multiple shader passes and their private variables

I know that multi pass rendering is about rendering separate parts of the scene and combining them into on image with blending factors applied , this has been done in rendering graphics. but What is a pass and What are multiple …

Read More
How to get the GL library/headers?

#include <gl\gl.h> #include <gl\glu.h> #include <gl\glaux.h> This is an example, but where to get GL headers?

Read More