QT Canvas3D能夠和好與qml其他組件融爲一體,在同一窗口顯示,這是目前QT 3D不具備的。QT 3D是比QT Canvas更加高級更加傻瓜化的api,但是沒有了基礎的繪圖函數,只能以組件爲最基礎的設計單元,更加細節的內容需要導入模型或者藉助其他手段。
而Canvas3D作爲更加基礎的3D繪圖api庫有更加靈活運用。而且在開發活躍度上更勝一籌,這是因爲Canvas3D直接使用webgl的api或者three.js,後者開發者達到了700人之多,這是QT 3D所不具備的。同時three.js的api比較人性化,容易理解,其功能層次介於webgl和QT 3D之間,相當於vtk之於C++,類似的庫還有xtk(後者主要用於醫學,而且已經基本停止開發)。
和vtk、xtk一樣,three.js裏有幾個重要概念:
- 相機camera
- 場景scene
- 燈光light
- 材料material
- 幾何體mesh
- 渲染器render
scene是個大容器,裝下了燈光和幾何體,材料是幾何體的屬性。設置好了場景和相機就可以開拍了,也就是渲染。
這個是本例的效果圖。
裏面用到了一個場景,一個相機,兩個燈光(左右各一),一個幾何體,其材料是能產生比較強的漫反射的lambert材料。另外在還有一個文字框懸在頂層,和3D組件互不干擾。
下面說代碼
js文件,作用是佈置場景和提供渲染接口給qml。
Qt.include("three.js")
var camera, scene, renderer,light;
var cube,line;
function initializeGL(canvas) {
scene = new THREE.Scene();
camera = new THREE.PerspectiveCamera(75, canvas.width / canvas.height, 0.1, 1000);
camera.position.z = 5;
camera.lookAt({x:0,y:0,z:0});
var leftLight = new THREE.DirectionalLight( 0xffffff, 0.5 );
leftLight.position.set( -1, 1, 1);
scene.add( leftLight );
var rightLight = new THREE.DirectionalLight( 0xffffff, 0.5 );
rightLight.position.set( 1, 1, 1);
scene.add( rightLight );
var material = new THREE.MeshLambertMaterial({ color: 0x80c342});
var cubeGeometry = new THREE.BoxGeometry(2, 2, 2);
cube = new THREE.Mesh(cubeGeometry, material);
scene.add(cube);
renderer = new THREE.Canvas3DRenderer(
{ canvas: canvas, antialias: true, devicePixelRatio: canvas.devicePixelRatio });
renderer.setSize(canvas.width, canvas.height);
}
function resizeGL(canvas) {
camera.aspect = canvas.width / canvas.height;
camera.updateProjectionMatrix();
renderer.setPixelRatio(canvas.devicePixelRatio);
renderer.setSize(canvas.width, canvas.height);
}
function paintGL(canvas) {
renderer.render(scene, camera);
}
function rotate(x,y,z){
cube.rotation.x+=x;
cube.rotation.y+=y;
cube.rotation.z+=z;
}
qml窗口界面的排版,調用js中的函數,這和html的作用是一樣的。
import QtQuick 2.4
import QtCanvas3D 1.1
import QtQuick.Window 2.2
import "glcode.js" as GLCode
Window {
title: qsTr("QT3js")
width: 1280
height: 768
visible: true
property int previousY: 0
property int previousX: 0
Canvas3D {
id: canvas3d
anchors.fill: parent
focus: true
property double xRot: 0.0
property double yRot: 45.0
property double distance: 2.0
onInitializeGL: {
GLCode.initializeGL(canvas3d);
}
onPaintGL: {
GLCode.paintGL(canvas3d);
}
onResizeGL: {
GLCode.resizeGL(canvas3d);
}
MouseArea {
anchors.fill: parent
onMouseXChanged: {
GLCode.rotate(0.1,0,0)
}
onMouseYChanged: {
GLCode.rotate(0,0.1,0)
}
onReleased: {
// Reset previous mouse positions to avoid rotation jumping
previousX = 0
previousY = 0
}
onWheel: {
canvas3d.distance -= wheel.angleDelta.y / 1000.0
// Limit the distance to 0.5...10
if (canvas3d.distance < 0.5)
canvas3d.distance = 0.5
if (canvas3d.distance > 10)
canvas3d.distance = 10
}
}
}
Rectangle {
id: rectangle1
x: 404
y: 180
width: 200
height: 101
color: "#baf1b3"
Text{
anchors.fill: parent
text:"hello"
verticalAlignment: Text.AlignVCenter
font.pointSize: 10
horizontalAlignment: Text.AlignHCenter
font.family: "Courier"
}
}
}