半透明物体边缘透射的简单模拟

最新推荐文章于 2024-10-19 02:32:03 发布

原创最新推荐文章于 2024-10-19 02:32:03 发布 · 4.1k 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#float #shader

图形专栏收录该内容

47 篇文章

订阅专栏

博客探讨模拟半透明物体边缘透射/散射效果，因看不懂SSS技术，考虑物体沿视线方向厚度及正对光源程度来实现。假设边缘更薄，给出用RenderMonkey写的简单shader代码，包含顶点着色器和像素着色器。

         半透明物体边缘透射/散射这样的效果应该用SSS(Sub-Surface Scatter)的技术来模拟,通俗点说就是玉的效果.但是本人数学不过关,看不懂SSS :-( ,.
        今天早上在想,如果考虑到物体的在沿着视线方向的厚度,以及正对光源的程度,是不是也可以出来点半透明的效果呢?
        来不及写一个程序来计算物体表面的厚度信息, 所以假设,越是边缘的地方,越薄.
        shader很简单. 用RenderMonkey写的。
http://xreal.51.net/Game/fakess.rfx

//Vertex Shader use GLSL
uniform vec3 fvLightPosition;
uniform vec3 fvEyePosition;

varying vec2 Texcoord;
varying vec3 ViewDirection;
varying vec3 LightDirection;
varying vec3 Normal;

void main( void )
{
   gl_Position = ftransform();
   Texcoord    = gl_MultiTexCoord0.xy;

   vec4 fvObjectPosition = gl_ModelViewMatrix * gl_Vertex;

   ViewDirection = fvEyePosition - fvObjectPosition.xyz;
   LightDirection = fvLightPosition - fvObjectPosition.xyz;
   Normal         = gl_NormalMatrix * gl_Normal;

}

//Pixel Shader use GLSL
uniform vec4 fvAmbient;
uniform vec4 fvSpecular;
uniform vec4 fvDiffuse;
uniform vec4 fvScatter;
uniform float fSpecularPower;
uniform float fLightPower;
uniform float fScatterPower;

uniform sampler2D baseMap;

varying vec2 Texcoord;
varying vec3 ViewDirection;
varying vec3 LightDirection;
varying vec3 Normal;

void main( void )
{
   vec3 fvLightDirection = normalize( LightDirection );
   vec3 fvNormal         = normalize( Normal );
   float fNDotL           = dot( fvNormal, fvLightDirection );

   vec3 fvReflection     = normalize( ( ( 2.0 * fvNormal ) * fNDotL ) - fvLightDirection );
   vec3 fvViewDirection = normalize( ViewDirection );
   float fRDotV           = max( 0.0, dot( fvReflection, fvViewDirection ) );

   vec4 fvBaseColor      = texture2D( baseMap, Texcoord );

   vec4 fvTotalAmbient   = fvAmbient ;
   vec4 fvTotalDiffuse   = fvDiffuse * fNDotL   * fvBaseColor;
   vec4 fvTotalSpecular = fvSpecular * ( pow( fRDotV, fSpecularPower ) );

   float    thickness = 1.0 - dot(fvViewDirection, fvNormal);
   float    viewness = fLightPower - fNDotL;
   vec4 vTrCl = fScatterPower   * viewness * thickness * fvScatter;
   gl_FragColor = vTrCl +    ( fvTotalAmbient + fvTotalDiffuse + fvTotalSpecular );

}