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Sonntag 5. September 2010
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O3D Tutorial 5: Eingaben über die Tastatur

Beitrag geschrieben von King of Darkness am 2010-04-19

Kurzbeschreibung:
In diesem Kapitel geht es darum wie man Eingaben über die Tastatur entgegen nimmt und verarbeitet.

Eingaben über die Tastatur zu empfangen ist in O3D sehr simpel. Wir erstellen einen Listener (Überwachungsfunktion) der auf eingaben wartet. Die Eingabe wird dann zu einem Handler (Funktion zum ausführen bzw. verarbeiten von Aktionen) geschickt der dann die Funktion ausführt mit der die gedrückte Taste verbunden ist.

Als erstes legen wir den Handler an. In diesem wollen wir die 3D Achse um einen bestimmten Winkel, definiert in delte drehen. Außerdem setzten wird das Flag actionTaken und geben es an die Aufrufende Funktion zurück.

Code:
         function keyPressedAction(keyPressed, delta) {
           var actionTaken = false;
           switch(keyPressed) {
             case 'a':
               g_3dRoot.localMatrix =
                   g_math.matrix4.mul(g_3dRoot.localMatrix,
                                 g_math.matrix4.rotationY(-delta));
               actionTaken = true;
               break;
             case 'd':
               g_3dRoot.localMatrix =
                   g_math.matrix4.mul(g_3dRoot.localMatrix,
                                 g_math.matrix4.rotationY(delta));
               actionTaken = true;
               break;
             case 'w':
               g_3dRoot.localMatrix =
                   g_math.matrix4.mul(g_3dRoot.localMatrix,
                                 g_math.matrix4.rotationX(-delta));
               actionTaken = true;
               break;
             case 's':
               g_3dRoot.localMatrix =
                   g_math.matrix4.mul(g_3dRoot.localMatrix,
                                 g_math.matrix4.rotationX(delta));
               actionTaken = true;
               break;
           }
           return actionTaken;
         }


Der hier genutzte Listener heißt keyPressedCallback. Als erstes wird geprüft ob die gedrückte Taste eine Zugriffstaste ist, wie z.B. Windowstaste oder auf dem MAC die Command Taste, dieses Tasten werden hier einfach ignoriert. Als nächstes wird der Buchstabe der gedrückt wurde in einen Kleinbuchstaben konvertiert, damit gehen wir dem Caps Lock aus dem Weg. Dann geben wir die Taste und den Drehwinkel den wir in einer Globalen Variable definiert haben zum Handler. Wenn die gedrückte Taste mit einer Aktion verbunden war brechen wir das Event ab, ansonsten wird die Eingabe an den Browser weitergeleitet. Damit lassen sich als Tasten die Normal vom Browser genutzt werden überschreiben.

Code:
         function keyPressedCallback(event) {
           event = event || window.event;

           if (event.metaKey)
             return;

           var keyChar =String.fromCharCode(o3djs.event.getEventKeyChar(event));
           keyChar = keyChar.toLowerCase();

           if (keyPressedAction(keyChar, g_keyPressDelta)) {
             o3djs.event.cancel(event);
           }
         }


Jetzt müssen wir nur noch die Listener in die Init Funktion mit einbauen:
Code:
window.document.onkeypress = keyPressedCallback;


Jetzt sollte es dir möglich sein den Würfel mit den Tasten W A S D nach oben, unten, links und rechts zu drehen.

Hier nun noch mal der Komplette Code:

Code:
<html>
   <head>
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <title>Tutorial 5: Capturing keyboard input</title>
      <script type="text/javascript" src="o3djs/base.js"></script>
      <script type="text/javascript">
         o3djs.require('o3djs.util');
         o3djs.require('o3djs.math');
         o3djs.require('o3djs.rendergraph');
         o3djs.require('o3djs.canvas');

         // Events
         // Run the init() function once the page has finished loading.
         // Run the uninit() function when the page has is unloaded.
         window.onload = init;
         window.onunload = uninit;

         // global variables
         var g_o3d;
         var g_math;
         var g_client;
         var g_pack;
         var g_clock = 0;
         var g_timeMult = 1;
         var g_cubeTransform;
         var g_textCanvas;
         var g_paint;
         var g_canvasLib;
         var g_3dRoot;
         var g_hudRoot;
         var g_viewInfo;
         var g_hudViewInfo;
         var g_keyPressDelta = 0.05;

         function createCube(material) {
           var cubeShape = g_pack.createObject('Shape');
           var cubePrimitive = g_pack.createObject('Primitive');
           var streamBank = g_pack.createObject('StreamBank');

           cubePrimitive.material = material;
           cubePrimitive.owner = cubeShape;
           cubePrimitive.streamBank = streamBank;

           cubePrimitive.primitiveType = g_o3d.Primitive.TRIANGLELIST;
           cubePrimitive.numberPrimitives = 12; // 12 triangles
           cubePrimitive.numberVertices = 8;    // 8 vertices in total

           var positionArray = [
             -0.5, -0.5,  0.5,  // vertex 0
              0.5, -0.5,  0.5,  // vertex 1
             -0.5,  0.5,  0.5,  // vertex 2
              0.5,  0.5,  0.5,  // vertex 3
             -0.5,  0.5, -0.5,  // vertex 4
              0.5,  0.5, -0.5,  // vertex 5
             -0.5, -0.5, -0.5,  // vertex 6
              0.5, -0.5, -0.5   // vertex 7
           ];

           var indicesArray = [
               0, 1, 2,  // face 1
               2, 1, 3,
               2, 3, 4,  // face 2
               4, 3, 5,
               4, 5, 6,  // face 3
               6, 5, 7,
               6, 7, 0,  // face 4
               0, 7, 1,
               1, 7, 3,  // face 5
               3, 7, 5,
               6, 0, 4,  // face 6
               4, 0, 2
           ];

           var positionsBuffer = g_pack.createObject('VertexBuffer');
           var positionsField = positionsBuffer.createField('FloatField', 3);
           positionsBuffer.set(positionArray);

           var indexBuffer = g_pack.createObject('IndexBuffer');
           indexBuffer.set(indicesArray);

           streamBank.setVertexStream(
               g_o3d.Stream.POSITION, // This stream stores vertex positions
               0,                     // First (and only) position stream
               positionsField,        // field: the field this stream uses.
               0);                    // start_index

           // Associate the triangle indices Buffer with the primitive.
           cubePrimitive.indexBuffer = indexBuffer;

           return cubeShape;
         }

         function drawText(str) {
           // Clear to completely transparent.
           g_textCanvas.canvas.clear([0.5, 0.5, 0.5, 0.5]);

           // Reuse the global paint object
           var paint = g_paint;
           paint.color = [1, 1, 1, 1];
           paint.textSize = 12;
           paint.textTypeface = 'Comic Sans MS';
           paint.textAlign = g_o3d.CanvasPaint.LEFT;
           paint.shader = null;
           g_textCanvas.canvas.drawText(str, 10, 30, paint);

           g_textCanvas.updateTexture();
        }        

         /**
          * This method gets called every time O3D renders a frame.  Here's
          * where we update the cube's transform to make it spin.
          * @param {o3d.RenderEvent} renderEvent The render event object that
          * gives us the elapsed time since the last time a frame was rendered.
          */
         function renderCallback(renderEvent) {
           g_clock += renderEvent.elapsedTime * g_timeMult;
           drawText("Hello world - " + (Math.round(g_clock * 100) / 100) + "s");
         }

         /**
          * Function performing the rotate action in response to a key-press.
          * Rotates the scene based on key pressed. (w ,s, a, d). Note that the
          * x, y-axis referenced here are relative to the current view of scene.
          * @param {keyPressed} The letter pressed, in lower case.
          * @param {delta} The angle by which the scene should be rotated.
          * @return true if an action was taken.
          */
         function keyPressedAction(keyPressed, delta) {
           var actionTaken = false;
           switch(keyPressed) {
             case 'a':

               g_3dRoot.localMatrix =
                   g_math.matrix4.mul(g_3dRoot.localMatrix,
                                      g_math.matrix4.rotationY(-delta));
               actionTaken = true;
               break;
             case 'd':
               g_3dRoot.localMatrix =
                   g_math.matrix4.mul(g_3dRoot.localMatrix,
                                      g_math.matrix4.rotationY(delta));
               actionTaken = true;
               break;
             case 'w':
               g_3dRoot.localMatrix =
                   g_math.matrix4.mul(g_3dRoot.localMatrix,
                                      g_math.matrix4.rotationX(-delta));
               actionTaken = true;
               break;
             case 's':
               g_3dRoot.localMatrix =
                   g_math.matrix4.mul(g_3dRoot.localMatrix,
                                      g_math.matrix4.rotationX(delta));
               actionTaken = true;
               break;
           }
           return actionTaken;
         }

         /**
          * Callback for the keypress event.
          * Invokes the action to be performed for the key pressed.
          * @param {event} keyPress event passed to us by javascript.
          */
         function keyPressedCallback(event) {
           event = event || window.event;

           // Ignore accelerator key messages.
           if (event.metaKey)
             return;

           var keyChar =String.fromCharCode(o3djs.event.getEventKeyChar(event));
           // Just in case they have capslock on.
           keyChar = keyChar.toLowerCase();

           if (keyPressedAction(keyChar, g_keyPressDelta)) {
             o3djs.event.cancel(event);
           }
         }        

         /**
          * Creates the client area.
          */
         function init() {
           o3djs.util.makeClients(initStep2);
         }

         /**
          * Initializes O3D.
          * @param {Array} clientElements Array of o3d object elements.
          */
         function initStep2(clientElements) {
           // Initializes global variables and libraries.
           var o3dElement = clientElements[0];
           g_client = o3dElement.client;
           g_o3d = o3dElement.o3d;
           g_math = o3djs.math;

           // Initialize O3D sample libraries.
           o3djs.base.init(o3dElement);

           // Create a pack to manage the objects created.
           g_pack = g_client.createPack();

           // Create 2 root transforms, one for the 3d parts and 2d parts.
           // This is not strictly neccassary but it is helpful.
           g_3dRoot = g_pack.createObject('Transform');
           g_hudRoot = g_pack.createObject('Transform');

           // Create the render graph for a view.
           g_viewInfo = o3djs.rendergraph.createBasicView(
               g_pack,
               g_3dRoot,
               g_client.renderGraphRoot);

           // Set the background color to black.
           g_viewInfo.clearBuffer.clearColor = [0, 0, 0, 1];

           // Create a second view for the hud.
           g_hudViewInfo = o3djs.rendergraph.createBasicView(
                g_pack,
                g_hudRoot,
                g_client.renderGraphRoot);

           // Make sure the hud gets drawn after the 3d stuff
           g_hudViewInfo.root.priority = g_viewInfo.root.priority + 1;

           // Turn off clearing the color for the hud since that would erase the
           // 3d parts but leave clearing the depth and stencil so the HUD is
           //  unaffected by anything done by the 3d parts.
           g_hudViewInfo.clearBuffer.clearColorFlag = false;

           // Set up a perspective view
           g_viewInfo.drawContext.projection = g_math.matrix4.perspective(
               g_math.degToRad(30), // 30 degree fov.
               g_client.width / g_client.height,
               1,                  // Near plane.
               5000);              // Far plane.

           // Set up our view transformation to look towards the world origin
           // where the cube is located.
           g_viewInfo.drawContext.view = g_math.matrix4.lookAt([0, 1, 5], //eye
                                                     [0, 0, 0],  // target
                                                     [0, 1, 0]); // up

           //Set up the 2d orthographic view
           g_hudViewInfo.drawContext.projection = g_math.matrix4.orthographic(
              0 + 0.5,
              g_client.width + 0.5,
              g_client.height + 0.5,
              0 + 0.5,
              0.001,
              1000);

           g_hudViewInfo.drawContext.view = g_math.matrix4.lookAt(
              [0, 0, 1],   // eye
              [0, 0, 0],   // target
              [0, 1, 0]);  // up                                                    

           // Create an Effect object and initialize it using the shaders
           // from the text area.
           var redEffect = g_pack.createObject('Effect');
           var shaderString = document.getElementById('effect').value;
           redEffect.loadFromFXString(shaderString);

           // Create a Material for the mesh.
           var redMaterial = g_pack.createObject('Material');

           // Set the material's drawList.
           redMaterial.drawList = g_viewInfo.performanceDrawList;

           // Apply our effect to this material. The effect tells the 3D
           // hardware which shaders to use.
           redMaterial.effect = redEffect;

           // Create the Shape for the cube mesh and assign its material.
           var cubeShape = createCube(redMaterial);

           // Create a new transform and parent the Shape under it.
           g_cubeTransform = g_pack.createObject('Transform');
           g_cubeTransform.addShape(cubeShape);

           // Parent the cube's transform to the client root.
           g_cubeTransform.parent = g_3dRoot;

           // Generate the draw elements for the cube shape.
           cubeShape.createDrawElements(g_pack, null);

           // Create the global paint object that's used by draw operations.
           g_paint = g_pack.createObject('CanvasPaint');

           // Creates an instance of the canvas utilities library.
           g_canvasLib = o3djs.canvas.create(g_pack, g_hudRoot, g_hudViewInfo);

           // Create a canvas that will be used to display the text.
           g_textCanvas = g_canvasLib.createXYQuad(70, 70, 0, 100, 50, true);
           // Set our render callback for animation.
           // This sets a function to be executed every time frame is rendered.
           g_client.setRenderCallback(renderCallback);

           //Set up a callback to interpret keypresses
           window.document.onkeypress = keyPressedCallback;
         }

         /**
          * Removes callbacks so they aren't called after the page has unloaded.
          */
         function uninit() {
           if (g_client) {
             g_client.cleanup();
           }
         }

      </script>
   </head>
   <body>
      <h1>Tutorial 5: Capturing keyboard input</h1>
      Use W, S, A, D to rotate the cube
      <br/>

      <div id="o3d" style="width: 300px; height: 300px;"></div>
      <div style="display:none">
         <!-- Start of effect -->
         <textarea id="effect">
           // World View Projection matrix that will transform
           // the input vertices to screen space.
           float4x4 worldViewProjection : WorldViewProjection;

           // input parameters for our vertex shader
           struct VertexShaderInput {
             float4 position : POSITION;
           };

           // input parameters for our pixel shader
           struct PixelShaderInput {
             float4 position : POSITION;
           };

           /**
            * The vertex shader simply transforms input vertices to screen space
            */
           PixelShaderInput vertexShaderFunction(VertexShaderInput input) {
             PixelShaderInput output;

             // Multiply the vertex positions by the worldViewProjection
             // matrix to transform them to screen space.
             output.position = mul(input.position, worldViewProjection);
             return output;
           }

           /**
            * This pixel shader just returns the color red.
            */
           float4 pixelShaderFunction(PixelShaderInput input): COLOR {
             return float4(1, 0, 0, 1);  // Red.
           }

           // Here we tell our effect file *which* functions are
           // our vertex and pixel shaders.

           // #o3d VertexShaderEntryPoint vertexShaderFunction
           // #o3d PixelShaderEntryPoint pixelShaderFunction
           // #o3d MatrixLoadOrder RowMajor
         </textarea>
         <!-- End of effect -->
    </div>
  </body>
</html>

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