为虚拟对象添加逼真的光照

了解如何在您自己的应用中使用照明估算。

前提条件

确保您了解基本 AR 概念以及如何配置 ARCore 会话，然后再继续。

使用适当模式在每次会话期间配置一次 API

在每个会话中为您要使用的模式配置一次光照估算。

Java

// Configure the session with the Lighting Estimation API in ENVIRONMENTAL_HDR mode.
Config config = session.getConfig();
config.setLightEstimationMode(LightEstimationMode.ENVIRONMENTAL_HDR);
session.configure(config);

// Configure the session with the Lighting Estimation API in AMBIENT_INTENSITY mode.
Config config = session.getConfig();
config.setLightEstimationMode(LightEstimationMode.AMBIENT_INTENSITY);
session.configure(config);

// Configure the session with the Lighting Estimation API turned off.
Config config = session.getConfig();
config.setLightEstimationMode(LightEstimationMode.DISABLED);
session.configure(config);

Kotlin

// Configure the session with the Lighting Estimation API in ENVIRONMENTAL_HDR mode.
Config config = session.config
config.lightEstimationMode = LightEstimationMode.ENVIRONMENTAL_HDR
session.configure(config)

// Configure the session with the Lighting Estimation API in AMBIENT_INTENSITY mode.
Config config = session.config
config.lightEstimationMode = LightEstimationMode.AMBIENT_INTENSITY
session.configure(config)

// Configure the session with the Lighting Estimation API turned off.
Config config = session.config
config.lightEstimationMode = LightEstimationMode.DISABLED
session.configure(config)

配置ENVIRONMENTAL_HDR模式

如需配置 ENVIRONMENTAL_HDR 模式，请获取每一帧的光估值，然后获取要使用的环境 HDR 光效组件。

Java

void update() {
  // Get the current frame.
  Frame frame = session.update();

  // Get the light estimate for the current frame.
  LightEstimate lightEstimate = frame.getLightEstimate();

  // Get intensity and direction of the main directional light from the current light estimate.
  float[] intensity = lightEstimate.getEnvironmentalHdrMainLightIntensity(); // note - currently only out param.
  float[] direction = lightEstimate.getEnvironmentalHdrMainLightDirection();
  app.setDirectionalLightValues(intensity, direction); // app-specific code.

  // Get ambient lighting as spherical harmonics coefficients.
  float[] harmonics = lightEstimate.getEnvironmentalHdrAmbientSphericalHarmonics();
  app.setAmbientSphericalHarmonicsLightValues(harmonics); // app-specific code.

  // Get HDR environmental lighting as a cubemap in linear color space.
  Image[] lightmaps = lightEstimate.acquireEnvironmentalHdrCubeMap();
  for (int i = 0; i < lightmaps.length /*should be 6*/; ++i) {
    app.uploadToTexture(i, lightmaps[i]);  // app-specific code.
  }
}

Kotlin

fun update() {
  // Get the current frame.
  val frame = session.update()

  // Get the light estimate for the current frame.
  val lightEstimate = frame.lightEstimate

  // Get intensity and direction of the main directional light from the current light estimate.
  val intensity = lightEstimate.environmentalHdrMainLightIntensity
  val direction = lightEstimate.environmentalHdrMainLightDirection
  app.setDirectionalLightValues(intensity, direction) // app-specific code.

  // Get ambient lighting as spherical harmonics coefficients.
  val harmonics = lightEstimate.environmentalHdrAmbientSphericalHarmonics
  app.ambientSphericalHarmonicsLightValues = harmonics // app-specific code.

  // Get HDR environmental lighting as a cubemap in linear color space.
  val lightMaps = lightEstimate.acquireEnvironmentalHdrCubeMap();
  for ((index, lightMap) in lightMaps.withIndex()) { // 6 maps total.
    app.uploadToTexture(index, lightMap); // app-specific code.
  }
}

配置AMBIENT_INTENSITY模式

如果您打算使用 AMBIENT_INTENSITY 模式的色彩校正组件，请先通过重复使用共享的分配，避免在每一帧上分配色彩校正。

Java

 // Avoid allocation on every frame.
float[] colorCorrection = new float[4];

Kotlin

val colorCorrection = floatArrayOf(0.0f, 0.0f, 0.0f, 0.0f)

获取每一帧的光估值，然后获取要使用的环境强度分量。

Java

void update() {
  // Get the current frame.
  Frame frame = session.update();

  // Get the light estimate for the current frame.
  LightEstimate lightEstimate = frame.getLightEstimate();

  // Get the pixel intensity of AMBIENT_INTENSITY mode.
  float pixelIntensity = lightEstimate.getPixelIntensity();

  // Read the pixel color correction of AMBIENT_INTENSITY mode into colorCorrection.
  lightEstimate.getColorCorrection(colorCorrection, 0);
}

Kotlin

fun update() {
    // Get the current frame.
  val frame = session.update()

  // Get the light estimate for the current frame.
  val lightEstimate = frame.lightEstimate

  // Get the pixel intensity of AMBIENT_INTENSITY mode.
  val pixelIntensity = lightEstimate.pixelIntensity

  // Read the pixel color correction of AMBIENT_INTENSITY mode into colorCorrection.
  lightEstimate.getColorCorrection(colorCorrection, 0)
}

利用 Environmental HDR API 确保节能

能量守恒的原则是，从表面反射的光线绝不会比照射表面之前的强度更强。此规则在基于物理的渲染中强制执行，但在视频游戏和移动应用中使用的旧版渲染流水线中通常会省略此规则。

如果您将基于物理的渲染管道与环境 HDR 光估测搭配使用，只需确保虚拟对象中使用了基于物理的材料即可。

但是，如果您未使用基于物理的流水线，则有以下几种选择：

  • 最理想解决方案是迁移到基于物理的流水线。

  • 但是，如果无法做到这一点，一种不错的权宜解决方法是将非物理材料的反照率值乘以节能系数。这样可以确保至少可以将 BRDF 着色模型转换为基于物理模型的模型。每个 BRDF 的系数都不同；例如，漫射反射的系数为 1/Pi。