# WebGL Simple Lighting Tutorial

## Easiest Method

## Introduction

This tutorial explains how to prepare very simple WebGL Lighting. In this example shaders apply lighting based on the X and Y vertex coordinates. This lesson covers the vertex and fragment shaders for the WebGL Simple Lighting on a Sphere example.

## The Vertex Shader

The vertex shader calculates values of light and dark
based on X and Y vertex coordinates.
The varyings `v_light`

and `v_dark`

then pass those calculations to the fragment shader.
The following listing includes the entire
vertex shader.

attribute vec4 a_position; attribute vec2 a_tex_coord0; varying vec2 v_tex_coord0; varying float v_light; varying float v_dark; uniform mat4 um4_matrix; uniform mat4 um4_pmatrix; void main(void) { // Multiply the current vertex // by the transformation and // perspective projection // matrices. vec4 v4_position = um4_pmatrix * um4_matrix * a_position; // Output the modified // vertex position gl_Position = v4_position; // Calculate lighting based // on both X and Y coordinates. v_light = 1.0 - (v4_position.y + 1.0) * 0.2; v_light *= 1.0 - (v4_position.x + 1.0) * 0.2; // Calculate dark based // on just the X coordinate. v_dark = (v4_position.x + 1.0) * 0.3; // Map the current vertex position in gl_Position // to the current texel. v_tex_coord0 = a_tex_coord0; }

## The Fragment Shader

The fragment shader simply subtracts
from each color channel, the
dark value received through varying
`v_dark`

.
The shader uses the light value
passed through varying `v_light`

as the alpha value.
For more complex and accurate examples
please refer to other
WebGL Examples.
Especially refer to the point light and specular light projects.
The following listing includes the entire fragment shader.

precision mediump float; uniform sampler2D u_sampler0; varying vec2 v_tex_coord0; varying float v_light; varying float v_dark; void main(void) { vec4 color0 = texture2D( u_sampler0, v_tex_coord0 ); // Reduce red, green, // and blue channels, // by the dark value. // Apply the light // as alpha. gl_FragColor = vec4( color0.r-v_dark, color0.g-v_dark, color0.b-v_dark, v_light ); }

## WebGL Sphere Preparation

The sphere was created in 3DS Max
then translated for
WebGL with Seven Thunder Software's
JavaScript DAE file translator.
Web browsers hang when attempting to process
too much data with *JavaScript*.
Therefore this example displays a
a sphere with only 16 segments.

However
the Glowing Earth
example loads a smoother sphere translated with
the *Windows* 3D DAE Translator.
Seven Thunder Software plans to offer the first few versions of 3D DAE Translator

*free*.

## Summary

This tutorial explaineds how to prepare very simple WebGL Lighting. In this example shaders apply lighting based on the X and Y vertex coordinates. This lesson covered the vertex and fragment shaders for the WebGL Simple Lighting on a Sphere example.