cesiumDemo/Source/Scene/BrdfLutGenerator.js

import BoundingRectangle from '../Core/BoundingRectangle.js';
import defined from '../Core/defined.js';
import defineProperties from '../Core/defineProperties.js';
import destroyObject from '../Core/destroyObject.js';
import PixelFormat from '../Core/PixelFormat.js';
import Framebuffer from '../Renderer/Framebuffer.js';
import PixelDatatype from '../Renderer/PixelDatatype.js';
import RenderState from '../Renderer/RenderState.js';
import Sampler from '../Renderer/Sampler.js';
import Texture from '../Renderer/Texture.js';
import TextureMagnificationFilter from '../Renderer/TextureMagnificationFilter.js';
import TextureMinificationFilter from '../Renderer/TextureMinificationFilter.js';
import TextureWrap from '../Renderer/TextureWrap.js';
import BrdfLutGeneratorFS from '../Shaders/BrdfLutGeneratorFS.js';

    /**
     * @private
     */
    function BrdfLutGenerator() {
        this._framebuffer = undefined;
        this._colorTexture = undefined;
        this._drawCommand = undefined;
    }

    defineProperties(BrdfLutGenerator.prototype, {
        colorTexture : {
            get : function() {
                return this._colorTexture;
            }
        }
    });

    function createCommand(generator, context) {
        var framebuffer = generator._framebuffer;

        var drawCommand = context.createViewportQuadCommand(BrdfLutGeneratorFS, {
            framebuffer : framebuffer,
            renderState : RenderState.fromCache({
                viewport : new BoundingRectangle(0.0, 0.0, 256.0, 256.0)
            })
        });

        generator._drawCommand = drawCommand;
    }

    function createFramebuffer(generator, context) {
        var colorTexture = new Texture({
            context : context,
            width : 256,
            height: 256,
            pixelFormat : PixelFormat.RGBA,
            pixelDatatype : PixelDatatype.UNSIGNED_BYTE,
            sampler : new Sampler({
                wrapS : TextureWrap.CLAMP_TO_EDGE,
                wrapT : TextureWrap.CLAMP_TO_EDGE,
                minificationFilter : TextureMinificationFilter.NEAREST,
                magnificationFilter : TextureMagnificationFilter.NEAREST
            })
        });

        generator._colorTexture = colorTexture;

        var framebuffer = new Framebuffer({
            context : context,
            colorTextures : [colorTexture],
            destroyAttachments : false
        });

        generator._framebuffer = framebuffer;
    }

    BrdfLutGenerator.prototype.update = function(frameState) {
        if (!defined(this._colorTexture)) {
            var context = frameState.context;

            createFramebuffer(this, context);
            createCommand(this, context);
            this._drawCommand.execute(context);
            this._framebuffer = this._framebuffer && this._framebuffer.destroy();
            this._drawCommand.shaderProgram = this._drawCommand.shaderProgram && this._drawCommand.shaderProgram.destroy();
        }
    };

    BrdfLutGenerator.prototype.isDestroyed = function() {
        return false;
    };

    BrdfLutGenerator.prototype.destroy = function() {
        this._colorTexture = this._colorTexture && this._colorTexture.destroy();
        return destroyObject(this);
    };
export default BrdfLutGenerator;