BabylonJS - 贴花

贴花就像贴在物体上的贴纸。贴纸图案是借助绘制在网格上的二维图像完成的（例如，游戏中的物体）。在游戏中，假设你有一支军队在发射子弹，需要在物体上看到子弹的印记。所以在 BabylonJS 中，这是使用贴花来完成的，当你点击任何物体时，你将在点击的位置绘制一个二维图像。

贴花用于在创建的网格上添加细节——例如子弹、孔洞等细节。在下面给出的演示链接中，我们使用一个图像并将其添加到导入的网格中。

要添加贴花，您可以使用以下代码：

var newDecal = BABYLON.Mesh.CreateDecal("decal", mesh, decalPosition, normal, decalSize, angle);

执行以下代码以在网格上添加贴花：

BABYLON.SceneLoader.ImportMesh("Shcroendiger'scat", "scenes/", "SSAOcat.babylon", scene, function (newMeshes) {
   var cat = newMeshes[0]; / /this is mesh shown on the screen.

   // Set the target of the camera to the first imported mesh
   camera.target = cat;

   var decalMaterial = new BABYLON.StandardMaterial("decalMat", scene);
   decalMaterial.diffuseTexture = new BABYLON.Texture("images/impact1.jpg", scene);
   decalMaterial.diffuseTexture.hasAlpha = true;
   decalMaterial.zOffset = -2;

   var onPointerDown = function (evt) {
      if (evt.button !== 0) {
         return;
      }

      // check if we are under a mesh
      var pickInfo = scene.pick(scene.pointerX, scene.pointerY, function (mesh) { return mesh === cat; 
      // this will give all the meshes , but it will pick the mesh whch is same as cat and return true if it is found });
      if (pickInfo.hit) { // if true
         var decalSize = new BABYLON.Vector3(5, 5, 5); //size of decal is defined

         var newDecal = BABYLON.Mesh.CreateDecal("decal", cat, pickInfo.pickedPoint, pickInfo.getNormal(true), decalSize); //decal is created 
         newDecal.material = decalMaterial; //decal material is added.
      }
   }
   var canvas = engine.getRenderingCanvas();
   canvas.addEventListener("pointerdown", onPointerDown, false);

   scene.onDispose = function () {
      canvas.removeEventListener("pointerdown", onPointerDown);
   }
});

演示

<!doctype html>
<html>
   <head>
      <meta charset = "utf-8">
      <title>BabylonJs - Basic Element-Creating Scene</title>
      <script src = "babylon.js"></script>
      <style>
         canvas {width: 100%; height: 100%;}
      </style>
   </head>

   <body>
      <canvas id = "renderCanvas"></canvas>
      <script type = "text/javascript">
         var canvas = document.getElementById("renderCanvas");
         var engine = new BABYLON.Engine(canvas, true);
         
         var createScene  = function() {
            var scene = new BABYLON.Scene(engine);

            //Adding a light
            var light = new BABYLON.HemisphericLight("Hemi", new BABYLON.Vector3(0, 1, 0), scene);

            //Adding an Arc Rotate Camera
            var camera = new BABYLON.ArcRotateCamera("Camera", -1.85, 1.2, 200, BABYLON.Vector3.Zero(), scene);

            camera.attachControl(canvas, true);

            // The first parameter can be used to specify which mesh to import. Here we import all meshes
            BABYLON.SceneLoader.ImportMesh("Shcroendiger'scat", "scenes/", "SSAOcat.babylon", scene, function (newMeshes) {
               var cat = newMeshes[0];

               // Set the target of the camera to the first imported mesh
               camera.target = cat;

               var decalMaterial = new BABYLON.StandardMaterial("decalMat", scene);
               decalMaterial.diffuseTexture = new BABYLON.Texture("images/impact1.jpg", scene);
               decalMaterial.diffuseTexture.hasAlpha = true;
               decalMaterial.zOffset = -2;

               var onPointerDown = function (evt) {
                  if (evt.button !== 0) {
                     return;
                  }

                  // check if we are under a mesh
                  var pickInfo = scene.pick(scene.pointerX, scene.pointerY, function (mesh) { return mesh === cat; });
                  if (pickInfo.hit) {
                     var decalSize = new BABYLON.Vector3(5, 5, 5);

                     var newDecal = BABYLON.Mesh.CreateDecal("decal", cat, pickInfo.pickedPoint, pickInfo.getNormal(true), decalSize);
                     newDecal.material = decalMaterial;
                  }
               }
               var canvas = engine.getRenderingCanvas();
               canvas.addEventListener("pointerdown", onPointerDown, false);

               scene.onDispose = function () {
                  canvas.removeEventListener("pointerdown", onPointerDown);
               }
            });	
            return scene;
         };
         var scene = createScene();
         engine.runRenderLoop(function() {
            scene.render();
         });
      </script>
   </body>
</html>

在上面的演示链接中，我们使用了 SSAOcat.babylon 网格。您可以从此处下载 SSAOcat.babylon 的 json 文件：

SSAOcat.babylon

将文件保存在 scenes/ 文件夹中。这将帮助您获得如下所示的输出。

输出

以上代码行生成以下输出：

在这个演示中，我们使用了图像 **impact1.jpg**。这些图像存储在本地 images/ 文件夹中，并也在下面粘贴供参考。您可以下载任何您选择的图像并在演示链接中使用。

images/impact1.jpg

打印页面