Away3D（九）：Lighting & shading

最新推荐文章于 2024-10-26 17:00:00 发布

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最新推荐文章于 2024-10-26 17:00:00 发布

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分类专栏： Away3D 文章标签： Flash 算法

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本文介绍了Away3D中的光照原理及材质类型，包括环境光、定向光、点光源等光源类型及其与不同材质（如PhongBitmapMaterial、EnviroBitmapMaterial）的交互方式，还提供了具体的代码示例。

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Away3D中的光照可以分为三个基本要素：

the light source(s) defining the properties of the light(s)
light source(s) 定义了光照的属性

shaders providing algorithms that determine how a light source interacts with a material
shaders 提供一些决定光源如何同材质交互的算法

a material type combining different shaders along with base colours or bitmaps
一种组合了不同 shaders 和 colors 或者 bitmaps 的 material type

第一个同PV3D不同之处是我们可以指定超过一个光源。这样会加大CPU的负担，但同时也可以制造出更加真实的场景渲染。

三种主要的 light sources：

AmbientLight3D which has no position and provides a uniform ambient light to all objects
AmbientLight3D （环境光源）没有空间坐标，他为所有的 object 提供了一种统一的环境光照

DirectionalLight3D which provides light from a specified position but with a strength that does not diminish with distance
DirectionalLight3D （定向光源），有一个空间坐标，有一个不会减弱的光照强度

PointLight3D providing light from a specified position that weakens in intensity with distance
PointLight3D （点光源），有一个空间坐标，光照强度会随着距离的增加而减弱

以下几种 shaders：

AmbientShader which provides ambient shading to a triangle face
AmbientShader 为一个三角面提供环境阴影

DiffusePhongShader which, depending on the angle between the light source and a triangle face, produces a diffuse shading pattern
DiffusePhongShader 根据光源和三角面之间所成的角度，产生一个散射阴影

SpecularPhongShader which produces specular shading on triangles to imitate a surface that is reflecting light, depending on the observer’s position and the light position
SpecularPhongShader 根据观察者和光源的位置，为三角面产生一个模拟的反射光源的效果

EnviroShader allowing for environment mapping, producing a reflection from a surrounding environment on an object, independent of a light source. Requires bitmap data for the environment
EnviroShader 根据光源位置和环境贴图，给 object 添加一个环境贴图反射的映射

DiffuseDot3Shader to increase scene reality by adding more small scale structure through the use of normal mapping to an object. Requires bitmap data for the normal map
DiffuseDot3Shader 通过增加更多的 structure 来增加场景的真实感

以上shaders，除了 EnviroShader ，其余的 light source 都是DirectionalLight3D

我们可以选择使用CompositeMaterials ，这种材质包含了一些不同的 shaders 和基于这些 shaders 的materials。

material列表如下：

PhongBitmapMaterial used to create ambient, diffuse and specular lighting on a texture-mapped material

Base material : BitmapMaterial

Shaders : AmbientShader , DiffusePhongShader and SpecularPhongShader

PhongMovieMaterial used to create ambient, diffuse and specular lighting on a material based on another Flash movie

Base material : MovieMaterial

Shaders : AmbientShader , DiffusePhongShader and SpecularPhongShader

PhongColorMaterial used to create ambient, diffuse and specular lighting on a simple coloured material

Base material : ColorMaterial

Shaders : AmbientShader , DiffusePhongShader and SpecularPhongShader

EnviroBitmapMaterial used to create environmental lighting on a texture-mapped material

Base material : BitmapMaterial

Shaders : EnviroShader

Dot3BitmapMaterial used to create ambient and normal-mapped lighting on a texture-mapped material

Base material : BitmapMaterial

Shaders : AmbientShader and DiffuseDot3Shader ,

Dot3MovieMaterial used to create ambient and normal-mapped lighting on a material based on another Flash movie

Base material : MovieMaterial

Shaders : AmbientShader and DiffuseDot3Shader

以上这些 materials 都是很耗性能的，如果你想使用简单点的 shade ，你可以选择CenterLightingMaterial 这种材质的效果就相同于PV3D里的 flat-shaded materials ，Away3D里有两种选择：

ShadingColorMaterial for simple flat shading of a ColorMaterial
WhiteShadingBitmapMaterial for simple flat shading of a BitmapMaterial , but assuming that the light source is always white (independent of colour given to light source).

  // create a new directional white light source with specific ambient, diffuse and specular parameters
  var light:DirectionalLight3D = new DirectionalLight3D({color:0xFFFFFF, ambient:0.25, diffuse:0.75, specular:0.9});
  light.x = 100;
  light.z = 500;
  light.y = 500;
  scene.addChild(light);

  // Create an object container to group the objects on the scene
  group = new ObjectContainer3D();
  scene.addChild(group);
   
  // Create a new sphere object using a very shiny phong-shaded bitmap material representing the earth
  var earthMaterial:PhongBitmapMaterial = new PhongBitmapMaterial(Cast.bitmap(earthBitmap));
  earthMaterial.shininess = 100;
  sphere = new Sphere({material:earthMaterial, radius:50, segmentsW:10, segmentsH:10});
  sphere.x = ORBITAL_RADIUS;
  sphere.ownCanvas = true;
  group.addChild(sphere);

  // Create a new cube object using a tiled, phong-shaded bitmap material
  var tiledAway3DMaterial:PhongBitmapMaterial = new PhongBitmapMaterial(Cast.bitmap(away3DBitmap), {repeat:true, scaleX:.5, scaleY:.5});
  cube = new Cube({material:tiledAway3DMaterial, width:75, height:75, depth:75});
  cube.z = -ORBITAL_RADIUS;
  cube.ownCanvas = true;
  group.addChild(cube);
 
  // Create a cylinder mapping the earth data again
  cylinder = new Cylinder({material:earthMaterial, radius:25, height:100, segmentsW:16});
  cylinder.x = -ORBITAL_RADIUS;
  cylinder.ownCanvas = true;
  group.addChild(cylinder);
 
  // Create a torus object and use a checkered, flat-shaded (from white light) bitmap material
  var checkerBitmapMaterial:WhiteShadingBitmapMaterial = new WhiteShadingBitmapMaterial(Cast.bitmap(checkerBitmap));
  torus = new Torus({material:checkerBitmapMaterial, radius:40, tube:10, segmentsT:8, segmentsR:16});
  torus.z = ORBITAL_RADIUS;
  torus.ownCanvas = true;
  group.addChild(torus);
 
  // Create a new cube object using a smoothed, precise, phong-shaded, mat (not shiny) bitmap material
  var away3DMaterial:PhongBitmapMaterial = new PhongBitmapMaterial(Cast.bitmap(away3DBitmap), {smooth:true, precision:2});
  away3DMaterial.shininess = 0;
  centerCube = new Cube({material:away3DMaterial, width:75, height:75, depth:75});
  centerCube.ownCanvas = true;
  group.addChild(centerCube);

  // add mouse listeners to all the 3D objects
  sphere.addOnMouseDown(onMouseDownOnObject);
  cube.addOnMouseDown(onMouseDownOnObject);
  cylinder.addOnMouseDown(onMouseDownOnObject);
  torus.addOnMouseDown(onMouseDownOnObject);
  centerCube.addOnMouseDown(onMouseDownOnObject);