LWJGL 3中Phong着色的镜面光照失效问题

我在自研引擎中实现了光照效果，但物体无法正常发光，镜面光照完全失效。将float diffuseFactor = max(dot(normal, to_light_dir ), 0.0);和float specularFactor = max(dot(camera_direction, reflected_light), 0.0);中的0.0改为0.1等大于0的值后，效果有所变化，但镜面光照仍完全失效。

顶点着色器代码 #

#version 330

layout (location = 0) in vec3 position;
layout (location = 1) in vec2 tex_coords;
layout (location = 2) in vec3 normals;

uniform mat4 projectionMatrix;
uniform mat4 worldMatrix;
uniform mat4 viewMatrix;

out vec2 coords;
out vec3 vertexNormals;
out vec3 vertexPos;

void main() {
    vec4 mVerPos = worldMatrix * vec4(position, 1.0);
    gl_Position = projectionMatrix * viewMatrix * worldMatrix * vec4(position, 1.0);
    coords = tex_coords;
    vertexNormals = normalize(worldMatrix * vec4(normals, 0.0)).xyz;
    vertexPos = mVerPos.xyz;
}

片段着色器代码 #

#version 330

struct Material {
    vec4 ambient;
    vec4 diffuse;
    vec4 specular;
    int hasTexture;
    float reflectance;
};

struct PointLight {
    vec3 color;
    vec3 position;
    float intensity;
    float constant;
    float linear;
    float exponent;
};

struct DirLight {
    vec3 position;
    vec3 color;
    float intensity;
};

out vec4 fragColor;

in vec2 coords;
in vec3 vertexNormals;
in vec3 vertexPos;

uniform sampler2D sampler;
uniform vec3 ambientColor;
uniform Material material;
uniform PointLight pointLight;
uniform float specularPower;
uniform DirLight dirLight;

vec4 ambientC;
vec4 diffuseC;
vec4 specularC;

void setUpColor(Material material, vec2 coords) {
    if (material.hasTexture == 1) {
        ambientC = texture(sampler, coords);
        diffuseC = ambientC;
        specularC = ambientC;
    }
    else {
        ambientC = material.ambient;
        diffuseC = material.diffuse;
        specularC = material.specular;
    }
}

vec4 calcLightColor(vec3 lightColor, float lightIntensity, vec3 position, vec3 to_light_dir, vec3 normal) {
    vec4 diffuseColour = vec4(0, 0, 0, 0);
    vec4 specColour = vec4(0, 0, 0, 0);

    // Diffuse Light
    float diffuseFactor = max(dot(normal, to_light_dir ), 0.0);
    diffuseColour = diffuseC * vec4(lightColor, 1.0) * lightIntensity * diffuseFactor;

    // Specular Light
    vec3 camera_direction = normalize(-position);
    vec3 from_light_dir = -to_light_dir;
    vec3 reflected_light = normalize(reflect(from_light_dir, normal));
    float specularFactor = max(dot(camera_direction, reflected_light), 0.0);
    specularFactor = pow(specularFactor, specularPower);
    specColour = specularC * lightIntensity * specularFactor * material.reflectance * vec4(lightColor, 1.0);
    
    return (diffuseColour + specColour);
};


vec4 calcPointLight(PointLight light, vec3 position, vec3 normal)
{
    vec3 light_direction = light.position - position;
    vec3 to_light_source  = normalize(light_direction);
    vec4 lightColor = calcLightColor(light.color, light.intensity, position, to_light_source, normal);

    // Attenuation
    float distance = length(light_direction);
    float attenuationInv = light.constant + light.linear * distance +
        light.exponent * distance * distance;
    return lightColor / attenuationInv;
}

vec4 calcDirLight(DirLight light, vec3 position, vec3 normal) {
    return calcLightColor(light.color, light.intensity, position, normalize(light.position), normal);
}

void main() {

    setUpColor(material, coords);
    vec4 diffuseSpecularComp = calcDirLight(dirLight, vertexPos, vertexNormals);
    diffuseSpecularComp += calcPointLight(pointLight, vertexPos, vertexNormals);
    fragColor = ambientC * vec4(ambientColor, 1) + diffuseSpecularComp;
    
}

问题排查与修复方案 #

• 修正法线变换逻辑：
  直接用worldMatrix变换法线会在非均匀缩放时出错，必须使用法线矩阵（世界矩阵的逆转置）：

  // 顶点着色器中替换法线变换代码
  vertexNormals = normalize(mat3(inverse(transpose(worldMatrix))) * normals);
  

• 修复相机方向计算：
  当前相机方向计算错误，需要传入相机的世界空间位置，计算从顶点指向相机的方向：

  // 片段着色器中添加相机位置uniform
  uniform vec3 cameraWorldPos;
  // 在calcLightColor函数中修改相机方向计算
  vec3 camera_direction = normalize(cameraWorldPos - position);
  

• 检查镜面光参数配置：
  • 确认material.specular不是黑色（比如设置为vec4(1.0,1.0,1.0,1.0)）
  • material.reflectance值应大于0（比如0.5~1.0）
  • specularPower建议设置为32、64或更高，过小会导致高光过于分散
• 修正方向光方向：
  DirLight的position字段被误用为方向，正确的方向光方向应该是从顶点指向光源的反方向，修改calcDirLight函数：

  vec4 calcDirLight(DirLight light, vec3 position, vec3 normal) {
      // 假设light.position是光源方向，取反得到指向光源的方向
      vec3 to_light_dir = normalize(-light.position);
      return calcLightColor(light.color, light.intensity, position, to_light_dir, normal);
  }
  

• 优化纹理镜面光处理：
  使用纹理时，不要直接用漫反射纹理作为镜面纹理，建议单独设置镜面纹理或使用材质的镜面颜色：

  // 修改setUpColor函数中的镜面颜色赋值
  if (material.hasTexture == 1) {
      ambientC = texture(sampler, coords);
      diffuseC = ambientC;
      specularC = material.specular; // 使用材质镜面颜色而非纹理
  }
  

内容的提问来源于stack exchange，提问作者Ajinkya Sanas