Texture

Offscreen Render Texture

Offscreen render texture, as the name suggests, can be obtained through offscreen rendering. It uses FBO technology at the underlying level, redirecting rendering operations from the screen to a texture. This texture can be used to achieve post-processing effects, refraction, reflection, dynamic environment mapping, and other artistic creations.

The engine provides the RenderTarget class for offscreen rendering and obtaining the corresponding offscreen render texture. Currently, the engine supports generating the following offscreen render textures:

Type	Application
Color Texture (Texture)	Can input a single color texture, multiple color textures (MRT), or a color cube texture
Depth Texture (Texture)	Can input a depth texture or a depth cube texture
Texture Combination	Color texture + depth texture, color cube texture + depth cube texture, multiple color textures + depth texture

Usage

Here is an example using the onBeginRender hook script. Before rendering each frame, first render the screen Object A to the offscreen texture, then use the offscreen texture as the base texture for Object B, and render Object B to the screen. Assume the layer of Object A is Layer0 and the layer of Object B is Layer1;

class switchRTScript extends Script {
    renderColorTexture = new Texture2D(engine, 1024, 1024);
    renderTarget = new RenderTarget(
      engine,
      1024,
      1024,
      this.renderColorTexture
    );

    constructor(entity: Entity) {
      super(entity);
	  // 将离屏纹理当作物体B的基础纹理
      materialB.baseTexture = this.renderColorTexture;
    }

    onBeginRender(camera: Camera) {
	  // 渲染物体A
      camera.renderTarget = this.renderTarget;
      camera.cullingMask = Layer.Layer0;
      camera.render();

	  // 还原 RT，接下来渲染物体B到屏幕。
      camera.renderTarget = null;
      camera.cullingMask = Layer.Layer1;
    }
  }

  cameraEntity.addComponent(switchRTScript);

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