使用 Phong 模型的点光源照明

Question

我希望使用 Phong 照明方案渲染一个包含一个盒子和一个点光源的场景。以下是我计算的相关代码sn-ps：

R3Rgb Phong(R3Scene *scene, R3Ray *ray, R3Intersection *intersection)
{
  R3Rgb radiance;
  if(intersection->hit == 0)
  {
    radiance = scene->background;
    return radiance;
  }

  ...
  // obtain ambient term
  ... // this is zero for my test

  // obtain emissive term
  ... // this is also zero for my test

  // for each light in the scene, obtain calculate the diffuse and specular terms
  R3Rgb intensity_diffuse(0,0,0,1);
  R3Rgb intensity_specular(0,0,0,1);
  for(unsigned int i = 0; i < scene->lights.size(); i++)
  {
    R3Light *light = scene->Light(i);
    R3Rgb light_color = LightIntensity(scene->Light(i), intersection->position);
    R3Vector light_vector = -LightDirection(scene->Light(i), intersection->position);

    // check if the light is "behind" the surface normal
    if(normal.Dot(light_vector)<=0)
      continue;

    // calculate diffuse reflection
    if(!Kd.IsBlack())
      intensity_diffuse += Kd*normal.Dot(light_vector)*light_color;

    if(Ks.IsBlack())
      continue;

    // calculate specular reflection
    ... // this I believe to be irrelevant for the particular test I'm doing

  }

  radiance = intensity_diffuse;
  return radiance;
}

R3Rgb LightIntensity(R3Light *light, R3Point position)
{
  R3Rgb light_intensity;
  double distance;
  double denominator;
  if(light->type != R3_DIRECTIONAL_LIGHT)
  {
    distance = (position-light->position).Length();
    denominator = light->constant_attenuation + 
                         (light->linear_attenuation*distance) + 
                         (light->quadratic_attenuation*distance*distance);
  }   

  switch(light->type)
  {
    ...

    case R3_POINT_LIGHT:
      light_intensity = light->color/denominator;
      break;

    ...
  }
  return light_intensity;
}

R3Vector LightDirection(R3Light *light, R3Point position)
{
  R3Vector light_direction;
  switch(light->type)
  {
    ...
    case R3_POINT_LIGHT:
      light_direction = position - light->position;
      break;
    ...
  }
  light_direction.Normalize();
  return light_direction;
}

我相信错误一定是在 LightDirection(...) 或 LightIntensity(...) 函数中的某个地方，因为当我使用定向光源运行我的代码时，我获得了所需的渲染图像（因此这让我相信 Phong 照明等式是正确的）。此外，在 Phong(...) 中，当我计算 intensity_diffuse 并在调试时，我将 light_color 除以 10，我得到的结果图像看起来更像我需要的。我是否正确计算了light_color？

谢谢。

Answer 1

原来我没有错误。我用来比较结果的“最终图像”计算不正确。