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<!--
O3D Tutorial B5
In this tutorial, we generate a simple spherical mesh using Javascript and
shade it using Phong illumination.
We calculate the various lighting components (ambient,diffuse,specular)
and combine them in our vertex/pixel shaders to draw the correct color for each
pixel in the scene.
The scene is illuminated by a single red light and the sphere is white.
(ie ambient, diffuse, and specular reflection constants of the material = 1)
In this sample, we generate the projection matrix dynamically from the size
of the o3d plugin.
-->
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>
Tutorial B5: Phong Shading
</title>
<!-- Our javascript code -->
<script type="text/javascript" src="o3djs/base.js"></script>
<script type="text/javascript" id="o3dscript">
o3djs.require('o3djs.util');
o3djs.require('o3djs.math');
o3djs.require('o3djs.rendergraph');
o3djs.require('o3djs.primitives');
// Events
// Run the init() function once the page has finished loading.
// unload() when the page is unloaded.
window.onload = init;
window.onunload = unload;
// global variables
var g_o3d;
var g_math;
var g_client;
var g_o3dElement;
var g_viewInfo;
var g_pack;
var g_o3dWidth = -1;
var g_o3dHeight = -1;
// Our view and projection matrices
// The view matrix transforms objects from world space to view space.
var g_view_matrix;
// The projection matrix projects objects from view space to the screen.
var g_proj_matrix;
/**
* Creates the client area.
*/
function init() {
o3djs.util.makeClients(initStep2);
}
/**
* Initializes O3D, loads the effect, and draws the sphere.
* @param {Array} clientElements Array of o3d object elements.
*/
function initStep2(clientElements) {
// Initializes global variables and libraries.
g_o3dElement = clientElements[0];
g_o3d = g_o3dElement.o3d;
g_math = o3djs.math;
g_client = g_o3dElement.client;
// Create a g_pack to manage our resources/assets
g_pack = g_client.createPack();
// Create the render graph for a view.
g_viewInfo = o3djs.rendergraph.createBasicView(
g_pack,
g_client.root,
g_client.renderGraphRoot);
/* Load the effect for our sphere from our file.
Effects, stored in a hidden textarea for simplicity, contain the
functions that define the vertex and pixel shaders used by our shape.
Here, we calculate phong illumination in our vertex shader and pass the
resultant color to our pixel shader, which does nothing except output its
given (input) color.
*/
var effect = g_pack.createObject('Effect');
effect.loadFromFXString(document.getElementById('shader').value);
// Create a Material for the effect.
var myMaterial = g_pack.createObject('Material');
// Apply our effect to this material.
myMaterial.effect = effect;
// Set the material's drawList
myMaterial.drawList = g_viewInfo.performanceDrawList;
// Create the params the effect needs on the material.
effect.createUniformParameters(myMaterial);
// Create a sphere at the origin with radius 1.
var myShape = o3djs.primitives.createSphere(g_pack,
myMaterial,
1,
70,
70);
// Set up the individual parameters in our effect file.
// Light position
var light_pos_param = myMaterial.getParam('light_pos');
light_pos_param.value = [10, 10, 20];
// Phong components of the light source
var light_ambient_param = myMaterial.getParam('light_ambient');
var light_diffuse_param = myMaterial.getParam('light_diffuse');
var light_specular_param = myMaterial.getParam('light_specular');
// White ambient light
light_ambient_param.value = [0.04, 0.04, 0.04, 1];
// Reddish diffuse light
light_diffuse_param.value = [0.8, 0, 0, 1];
// White specular light
light_specular_param.value = [0.5, 0.5, 0.5, 1];
// Shininess of the material (for specular lighting)
var shininess_param = myMaterial.getParam('shininess');
shininess_param.value = 30.0;
// Position of the camera.
// (should be the same as the 'eye' position given below)
var camera_pos_param = myMaterial.getParam('camera_pos');
// Camera is at (0, 0, 3).
camera_pos_param.value = [0, 0, 3];
// Now create our view matrix by defining coordinates for the
// target, eye, and up vectors and using the g_math.matrix4.lookAt(..)
// helper function to create the matrix.
// Eye-position, this is where our camera is at.
var eye = [0, 0, 3];
// Target, this is where our camera is pointed at.
var target = [0, 0, 0];
// Up-vector, this tells the camera which direction is 'up'.
// We define the positive y-direction to be up in this example.
var up = [0, 1, 0];
g_view_matrix = g_math.matrix4.lookAt(eye, target, up);
// Generate the projection and viewProjection matrices based
// on the g_o3d plugin size by calling resize().
resize();
// Now attach the sphere to the root of the transform graph.
var root = g_client.root;
root.addShape(myShape);
// If we don't check the size of the client area every frame we don't get a
// chance to adjust the perspective matrix fast enough to keep up with the
// browser resizing us.
g_client.setRenderCallback(resize);
}
// Generates the projection matrix based on the size of the o3d plugin
// and calculates the view-projection matrix.
function resize() {
var newWidth = g_client.width;
var newHeight = g_client.height;
if (newWidth != g_o3dWidth || newHeight != g_o3dHeight) {
g_o3dWidth = newWidth;
g_o3dHeight = newHeight;
// Create our projection matrix, with a vertical field of view of 45 degrees
// a near clipping plane of 0.1 and far clipping plane of 100.
g_proj_matrix = g_math.matrix4.perspective(
g_math.degToRad(45),
g_o3dWidth / g_o3dHeight,
0.1,
100);
// Set the view and projection matrix
g_viewInfo.drawContext.view = g_view_matrix;
g_viewInfo.drawContext.projection = g_proj_matrix;
}
}
/**
* Removes any callbacks so they don't get called after the page has unloaded.
*/
function unload() {
if (g_client) {
g_client.cleanup();
}
}
</script>
</head>
<body>
<table width="100%" style="height:100%;">
<tr><td>
<h1>Phong shading</h1>
<p>
This tutorial shows how we generate a custom mesh and
perform Phong illumination using a shader.
</p>
<p>
This sample displays a Phong shaded white sphere lit by a single red light.
</p>
<table id="container" width="90%" style="height:60%;"><tr><td height="100%">
<!-- Start of g_o3d plugin -->
<div id="o3d" style="width: 600px; height: 600px;"></div>
<!-- End of g_o3d plugin -->
</td></tr></table>
<!-- a simple way to get a multiline string -->
<textarea id="shader" name="shader" cols="80" rows="20"
style="display: none;">
// The 4x4 world view projection matrix.
float4x4 worldViewProjection : WorldViewProjection;
// positions of the light and camera
float3 light_pos;
float3 camera_pos;
// phong lighting components of the light source
float4 light_ambient;
float4 light_diffuse;
float4 light_specular;
// shininess of the material. (for specular lighting)
float shininess;
// input parameters for our vertex shader
struct VertexShaderInput {
float4 postion : POSITION;
float3 normal : NORMAL;
float4 color : COLOR;
};
// input parameters for our pixel shader
// also the output parameters for our vertex shader
struct PixelShaderInput {
float4 postion : POSITION;
float3 lightVector : TEXCOORD0;
float3 normal : TEXCOORD1;
float3 viewPosition : TEXCOORD2;
float4 color : COLOR;
};
/**
* Vertex Shader - vertex shader for phong illumination
*/
PixelShaderInput vertexShaderFunction(VertexShaderInput input) {
/**
* We use the standard phong illumination equation here.
* We restrict (clamp) the dot products so that we
* don't get any negative values.
* All vectors are normalized for proper calculations.
*
* The output color is the summation of the
* ambient, diffuse, and specular contributions.
*
* Note that we have to transform each vertex and normal
* by the world view projection matrix first.
*/
PixelShaderInput output;
output.postion = mul(input.postion, worldViewProjection);
/**
* lightVector - light vector
* normal - normal vector
* viewPosition - view vector (from camera)
*/
// NOTE: In this case we do not need to multiply by any matrices since the
// WORLD transformation matrix is the identity. If you were moving the
// object such that the WORLD transform matrix was not the identity, you
// would need to multiply the normal by the WORLDINVERSETTRANSFORM matrix
// since the normal is in object space. Other values (light_pos, camera_pos)
// are already in world space.
float3 lightVector = light_pos - input.postion.xyz;
float3 normal = input.normal;
float3 viewPosition = camera_pos - input.postion.xyz;
output.lightVector = lightVector;
output.normal = normal;
output.viewPosition = viewPosition;
output.color = input.color;
return output;
}
/**
* Pixel Shader
*/
float4 pixelShaderFunction(PixelShaderInput input): COLOR {
float3 lightVector = normalize(input.lightVector);
float3 normal = normalize(input.normal);
float3 viewPosition = normalize(input.viewPosition);
float3 halfVector = normalize(lightVector + viewPosition);
// use lit function to calculate phong shading
// x component contains the ambient coefficient
// y component contains the diffuse coefficient:
// max(dot(normal, lightVector),0)
// z component contains the specular coefficient:
// dot(normal, lightVector) < 0 || dot(normal, halfVector) < 0 ?
// 0 : pow(dot(normal, halfVector), shininess)
// NOTE: This is actually Blinn-Phong shading, not Phong shading
// which would use the reflection vector instead of the half vector
float4 phong_coeff = lit(dot(normal, lightVector),
dot(normal, halfVector), shininess);
float4 ambient = light_ambient * phong_coeff.x * input.color;
float4 diffuse = light_diffuse * phong_coeff.y * input.color;
float4 specular = light_specular * phong_coeff.z * input.color;
return ambient + diffuse + specular;
}
// Here we tell our effect file *which* functions are
// our vertex and pixel shaders.
// #o3d VertexShaderEntryPoint vertexShaderFunction
// #o3d PixelShaderEntryPoint pixelShaderFunction
// #o3d MatrixLoadOrder RowMajor
</textarea>
</td></tr></table>
</body>
</html>
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