/**
     * Parses the <textures> block.
     * @param {textures block element} texturesNode
     */
    parseTextures(texturesNode) {
        // Parse block
        var children = texturesNode.children;

        this.textures = [];
        var numTextures = 0;

        // Any number of textures.
        for (var i = 0; i < children.length; i++) {

            if (children[i].nodeName != "texture") {
                this.onXMLMinorError("unknown tag <" + children[i].nodeName + ">");
                continue;
            }

            // Get id of the current texture.
            var textureId = this.reader.getString(children[i], 'id');
            if (textureId == null)
                return "no ID defined for texture";

            // Checks for repeated IDs.
            if (this.textures[textureId] != null)
                return "ID must be unique for each texture (conflict: ID = " + textureId + ")";

            // Specifications for the current texture.

            // Retrieves the file path.
            var path = this.reader.getString(children[i], 'file');
            if (!(path != null && path != ""))
                return "unable to parse the file path for texture ID = " + textureId;

            // Store Textures global information.
            var newTexture = new CGFappearance(this.scene);
            newTexture.loadTexture(path);
            this.textures[textureId] = newTexture;

            numTextures++;
        }

        this.log("Parsed textures");

        return null;
    }