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src/passes/SavePass.js

import {
	LinearFilter,
	RGBFormat,
	UnsignedByteType,
	WebGLRenderTarget
} from "three";

import { CopyMaterial } from "../materials";
import { Pass } from "./Pass";

/**
 * A pass that renders the result from a previous pass to another render target.
 */

export class SavePass extends Pass {

	/**
	 * Constructs a new save pass.
	 *
	 * @param {WebGLRenderTarget} [renderTarget] - A render target.
	 * @param {Boolean} [resize=true] - Whether the render target should adjust to the size of the input buffer.
	 */

	constructor(renderTarget, resize = true) {

		super("SavePass");

		this.setFullscreenMaterial(new CopyMaterial());

		this.needsSwap = false;

		/**
		 * The render target.
		 *
		 * @type {WebGLRenderTarget}
		 */

		this.renderTarget = renderTarget;

		if(renderTarget === undefined) {

			this.renderTarget = new WebGLRenderTarget(1, 1, {
				minFilter: LinearFilter,
				magFilter: LinearFilter,
				stencilBuffer: false,
				depthBuffer: false
			});

			this.renderTarget.texture.name = "SavePass.Target";

		}

		/**
		 * Indicates whether the render target should be resized automatically.
		 *
		 * @type {Boolean}
		 */

		this.resize = resize;

	}

	/**
	 * The saved texture.
	 *
	 * @type {Texture}
	 */

	get texture() {

		return this.renderTarget.texture;

	}

	/**
	 * Saves the input buffer.
	 *
	 * @param {WebGLRenderer} renderer - The renderer.
	 * @param {WebGLRenderTarget} inputBuffer - A frame buffer that contains the result of the previous pass.
	 * @param {WebGLRenderTarget} outputBuffer - A frame buffer that serves as the output render target unless this pass renders to screen.
	 * @param {Number} [deltaTime] - The time between the last frame and the current one in seconds.
	 * @param {Boolean} [stencilTest] - Indicates whether a stencil mask is active.
	 */

	render(renderer, inputBuffer, outputBuffer, deltaTime, stencilTest) {

		const material = this.getFullscreenMaterial();
		material.uniforms.inputBuffer.value = inputBuffer.texture;

		renderer.setRenderTarget(this.renderToScreen ? null : this.renderTarget);
		renderer.render(this.scene, this.camera);

	}

	/**
	 * Updates the size of this pass.
	 *
	 * @param {Number} width - The width.
	 * @param {Number} height - The height.
	 */

	setSize(width, height) {

		if(this.resize) {

			const w = Math.max(width, 1);
			const h = Math.max(height, 1);

			this.renderTarget.setSize(w, h);

		}

	}

	/**
	 * Performs initialization tasks.
	 *
	 * @param {WebGLRenderer} renderer - A renderer.
	 * @param {Boolean} alpha - Whether the renderer uses the alpha channel.
	 * @param {Number} frameBufferType - The type of the main frame buffers.
	 */

	initialize(renderer, alpha, frameBufferType) {

		if(!alpha && frameBufferType === UnsignedByteType) {

			this.renderTarget.texture.format = RGBFormat;

		}

		if(frameBufferType !== undefined) {

			this.renderTarget.texture.type = frameBufferType;

			if(frameBufferType !== UnsignedByteType) {

				const material = this.getFullscreenMaterial();
				material.defines.FRAMEBUFFER_PRECISION_HIGH = "1";

			}

		}

	}

}