为虚拟对象添加逼真的光照

了解如何使用测光 。

前提条件

确保您了解 AR 基础概念 以及如何在继续之前配置 ARCore 现场录像。

使用适当的模式，为每个会话配置一次 API

针对要使用的模式，在每次会话中配置一次光照估计。

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，请获取每一帧的光照估算量， 然后获取想要使用的环境 HDR 照明组件。

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分配来避免在每个帧上分配色彩校正。

Java

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

Kotlin

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

获取每一帧的光照估值，然后获取环境强度分量 资源。

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)
}

通过 Environmental HDR API 确保节能

节能原则是指从物体表面反射的光线 它的强度从未像表面一样。此规则在基于物理的渲染中会强制执行，但通常会从视频游戏和移动应用中使用的旧版渲染流水线中省略。

如果您将基于物理的渲染管道与 Environmental HDR 搭配使用 只需确保所用的材料是基于物理材料 虚拟对象。

但是，如果您不使用基于物理的流水线 选项：

• 对此，最好的解决方案是迁移到基于物理的流水线。

• 如果不能做到这一点，一个很好的解决办法是将 通过节能研究从非物理材料获得的反照率值 系数。这样至少可以确保 BRDF 着色模型 可以转换为物理存储。每个 BRDF 都有一个不同的因素 -- 例如，对于漫射反射，其值为 1/Pi。