OpenGL 4.0 GLSL 用多个光照模型

在多个光照模型中，我们需要计算每个光照模型的颜色值，然后把这些颜色值相加得到最终物体表面的颜色值。

通常，我们会创建一个统一的数组来存储光源的位置和光照强度（密度）(见下文shader）

如图：一个5个光源的场景

顶点shader

#version 430

layout (location = 0) in vec3 VertexPosition;
layout (location = 1) in vec3 VertexNormal;

out vec3 Color;

struct LightInfo {
  vec4 Position;  // Light position in eye coords.
  vec3 Intensity; // Light intesity (amb., diff., and spec.)
};
uniform LightInfo lights[5];

// Material parameters
uniform vec3 Kd;            // Diffuse reflectivity
uniform vec3 Ka;            // Ambient reflectivity
uniform vec3 Ks;            // Specular reflectivity
uniform float Shininess;    // Specular shininess factor

uniform mat4 ModelViewMatrix;
uniform mat3 NormalMatrix;
uniform mat4 ProjectionMatrix;
uniform mat4 MVP;

vec3 ads( int lightIndex, vec4 position, vec3 norm )
{
    vec3 s = normalize( vec3(lights[lightIndex].Position - position) );
    vec3 v = normalize(vec3(-position));
    vec3 r = reflect( -s, norm );
    vec3 I = lights[lightIndex].Intensity;
    return I * ( Ka + Kd * max( dot(s, norm), 0.0 ) +Ks * pow( max( dot(r,v), 0.0 ), Shininess ) );
}

void main()
{
    vec3 eyeNorm = normalize( NormalMatrix * VertexNormal);
    vec4 eyePosition = ModelViewMatrix * vec4(VertexPosition,1.0);

    // Evaluate the lighting equation, for each light
    Color = vec3(0.0);
    for( int i = 0; i < 5; i++ )
        Color += ads( i, eyePosition, eyeNorm );

    gl_Position = MVP * vec4(VertexPosition,1.0);
}

片元shader

#version 430

in vec3 Color;

layout( location = 0 ) out vec4 FragColor;

void main() {
    FragColor = vec4(Color, 1.0);
}