c++ - Phong 照明模型实际上并没有照亮任何东西

Question

我目前有一项任务是在 openGL/GLSL 中实现 Phong 光照模型。我目前正在使用的两个着色器如下。问题是，在片段着色器中，如果我不将 vColor 添加到 gl_FragColor，那么整个形状都是黑色的。但是，如果我确实添加了 vColor，那么整个形状就是完全没有光照的那种颜色。我已经尝试解决这个问题几个小时了，但没有成功。这是什么原因？是我的着色器有问题，还是 openGL 代码有问题？我正在使用一种 Material 和一个点光源，我将在着色器之后展示它们。

编辑:如果我设置 gl_FragColor = vec4(N, 1.0) 那么对象看起来像这样:

顶点着色器:

#version 150

in vec4 vPosition;
in vec3 vNormal;

uniform mat4 vMatrix;
uniform vec4 LightPosition;

out vec3 fNorm;
out vec3 fEye;
out vec3 fLight;

void main() {
  fNorm = vNormal;
  fEye = vPosition.xyz;
  fLight = LightPosition.xyz;

  if(LightPosition.w != 0.0) {
    fLight = LightPosition.xyz - vPosition.xyz;
  }

gl_Position = vMatrix * vPosition;
}

片段着色器:

#version 150

in vec3 fNorm;
in vec3 fLight;
in vec3 fEye;

uniform vec4 vColor;
uniform vec4 AmbientProduct, DiffuseProduct, SpecularProduct;
uniform mat4 vMatrix;
uniform vec4 LightPosition;
uniform float Shininess;

void main(){
    vec3 N = normalize(fNorm);
    vec3 E = normalize(fEye);
    vec3 L = normalize(fLight);
    vec3 H = normalize(L + E);

    vec4 ambient = AmbientProduct;

    float Kd = max(dot(L, N), 0.0);
    vec4 diffuse = Kd * DiffuseProduct;

    float Ks = pow(max(dot(N, H), 0.0), Shininess);
    vec4 specular = Ks * SpecularProduct;
    if(dot(L,N) < 0.0) 
        specular = vec4(0.0, 0.0, 0.0, 1.0); 

    gl_FragColor = vColor + ambient + diffuse + specular;
}

设置 Material 和灯光:

void init() {

    setMaterials(vec4(1.0, 0.0, 0.0, 0.0), //ambient
             vec4(1.0, 0.8, 0.0, 1.0), //diffuse
             vec4(1.0, 1.0, 1.0, 1.0), //specular
             100.0); //shine

    setLightSource(vec4(1.0, 0.0, 0.0, 1.0), //ambient
               vec4(1.0, 0.0, 0.0, 1.0), //diffuse
               vec4(1.0, 0.0, 0.0, 1.0), //specular
               vec4(1.0, 2.0, 3.0, 1.0)); //position

    setProducts();

    ....
}

/*
 * Sets the material properties for Phong lighting model.
 */
void setMaterials(vec4 amb, vec4 dif, vec4 spec, GLfloat s) {
    ambient = amb;
    diffuse = dif;
    specular = spec;
    shine = s;

    glUniform1f(vShininess, shine);
}

/*
 * Set light source properties.
 */
void setLightSource(vec4 amb, vec4 dif, vec4 spec, vec4 pos) {
    ambient0 = amb;
    diffuse0 = dif;
    specular0 = spec;
    light0_pos = pos;

    glUniform4fv(vLightPosition, 1, light0_pos);
}

/*
 * Find the products of materials components and light components.
 */
void setProducts(){
    vec4 ambientProduct = ambient * ambient0;
    vec4 diffuseProduct = diffuse * diffuse0;
    vec4 specularProduct = specular * specular0;

    glUniform4fv(vAmbientProduct, 1, ambientProduct);
    glUniform4fv(vDiffuseProduct, 1, diffuseProduct);
    glUniform4fv(vSpecularProduct, 1, specularProduct);

}

Answer 1

您的最终光照组合看起来不正确:

gl_FragColor = vColor + ambient + diffuse + specular;

应该是这样的

gl_FragColor = vColor * (ambient + diffuse) + specular;

即由物体反照率调制的光照。