libgdx：使用PerspectiveCamera不显示SpriteBatch

Question

虽然我确实掌握了OpenGL的基本知识，但我只是从libgdx开始。

我的问题是：为什么，拥有完全相同的代码但只从OrthographicCamera切换到PerspectiveCamera具有不再显示我的任何SpriteBatches的效果？

这是我使用的代码：

create（）方法：

public void create() {
    textureMesh = new Texture(Gdx.files.internal("data/texMeshTest.png"));
    textureSpriteBatch = new Texture(Gdx.files.internal("data/texSpriteBatchTest.png"));

    squareMesh = new Mesh(true, 4, 4, 
            new VertexAttribute(Usage.Position, 3, "a_position")
            ,new VertexAttribute(Usage.TextureCoordinates, 2, "a_texCoords")

    );

    squareMesh.setVertices(new float[] {
            squareXInitial, squareYInitial, squareZInitial,             0,1,    //lower left
            squareXInitial+squareSize, squareYInitial, squareZInitial,  1,1,    //lower right
            squareXInitial, squareYInitial+squareSize, squareZInitial,  0,0,    //upper left
            squareXInitial+squareSize, squareYInitial+squareSize, squareZInitial,1,0});  //upper right 

    squareMesh.setIndices(new short[] { 0, 1, 2, 3});

    spriteBatch = new SpriteBatch();        
}

和render（）方法：

public void render() {
    GLCommon gl = Gdx.gl;

    camera.update();
    camera.apply(Gdx.gl10);
    spriteBatch.setProjectionMatrix(camera.combined);

    gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
    gl.glEnable(GL10.GL_DEPTH_TEST);

    gl.glEnable(GL10.GL_TEXTURE_2D);
    textureMesh.bind();
    squareMesh.render(GL10.GL_TRIANGLE_STRIP, 0, 4);

    spriteBatch.begin();
    spriteBatch.draw(textureSpriteBatch, -10, 0);
    spriteBatch.end();        
}

现在，如果在我的resize（int width，int height）方法中，我设置了相机，如下所示：

   public void resize(int width, int height) {
        float aspectRatio = (float) width / (float) height;
        camera = new OrthographicCamera(cameraViewHeight * aspectRatio, cameraViewHeight);

我明白了：

但如果我更改相机类型：

public void resize(int width, int height) {
    float aspectRatio = (float) width / (float) height;
    camera = new PerspectiveCamera(64, cameraViewHeight * aspectRatio, cameraViewHeight);
}       

我明白了：

我问的原因是因为我真的很喜欢libgdx内置的在OpenGL中绘制文本（字体）的能力。 但是在他们的例子中，他们使用SpriteBatch，它们可以通向Font实例，并且它们也总是使用Ortho Camera。 我想知道SpriteBatch和Font绘图功能是否适用于PerspectiveCamera。

Answer 1

好吧，好吧，我解决了它：

简短回答：

SpriteBatch在内部使用OrthogonalPerspective。 如果使用PerspectiveCamera，则需要将自定义视图矩阵传递给SpriteBatch。 您可以在resize（...）方法中执行此操作：

@Override
public void resize(int width, int height) {
    float aspectRatio = (float) width / (float) height;
    camera = new PerspectiveCamera(64, cameraViewHeight * aspectRatio, cameraViewHeight);
    viewMatrix = new Matrix4();
    viewMatrix.setToOrtho2D(0, 0,width, height);
    spriteBatch.setProjectionMatrix(viewMatrix);
}

然后没有必要对该精灵的投影矩阵做任何其他事情（除非你想改变精灵在屏幕上的显示方式）：

public void render() {
    GLCommon gl = Gdx.gl;

    camera.update();
    camera.apply(Gdx.gl10);
    //this is no longer needed:
    //spriteBatch.setProjectionMatrix(camera.combined);
    //...

答案很长：因为我的最终目标是能够使用SpriteBatch来绘制文本，而对我的代码进行上述修改后我可以这样做，因为精灵上的文本和带纹理的网格都是现在可见了，我注意到如果我没有为网格的顶点指定颜色，那么顶点会得到我用于文本的颜色。 换句话说，使用如下声明的纹理网格：

 squareMesh = new Mesh(true, 4, 4, 
            new VertexAttribute(Usage.Position, 3, "a_position")
            ,new VertexAttribute(Usage.TextureCoordinates, 2, "a_texCoords")

    );

    squareMesh.setVertices(new float[] {
            squareXInitial, squareYInitial, squareZInitial,             0,1,    //lower left
            squareXInitial+squareSize, squareYInitial, squareZInitial,  1,1,    //lower right
            squareXInitial, squareYInitial+squareSize, squareZInitial,  0,0,    //upper left
            squareXInitial+squareSize, squareYInitial+squareSize, squareZInitial,1,0});  //upper right 

    squareMesh.setIndices(new short[] { 0, 1, 2, 3});

在我的render（...）方法中使用此代码也会使网格变为红色：

font.setColor(Color.RED);
spriteBatch.draw(textureSpriteBatch, 0, 0);
font.draw(spriteBatch, (int)fps+" fps", 0, 100);

解决这个问题的方法是从一开始就在网格的顶点上设置颜色：

squareMesh = new Mesh(true, 4, 4, 
        new VertexAttribute(Usage.Position, 3, "a_position")
        ,new VertexAttribute(Usage.ColorPacked, 4, "a_color")
        ,new VertexAttribute(Usage.TextureCoordinates, 2, "a_texCoords")

);

squareMesh.setVertices(new float[] {
        squareXInitial, squareYInitial, squareZInitial,                         Color.toFloatBits(255, 255, 255, 255),  0,1,    //lower left
        squareXInitial+squareSize, squareYInitial, squareZInitial,              Color.toFloatBits(255, 255, 255, 255),  1,1,    //lower right
        squareXInitial, squareYInitial+squareSize, squareZInitial,              Color.toFloatBits(255, 255, 255, 255),  0,0,    //upper left
        squareXInitial+squareSize, squareYInitial+squareSize, squareZInitial,   Color.toFloatBits(255, 255, 255, 255),  1,0});  //upper right 

squareMesh.setIndices(new short[] { 0, 1, 2, 3});