libgdx：SpriteBatch 未使用 PerspectiveCamera 显示

Question

虽然我有 OpenGL 的基本知识，但我只是从 libgdx 开始。

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

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，我像这样设置相机：

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

我明白了：

但是如果我改变相机类型：

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。但是在他们的示例中，他们使用了 SpriteBatch，他们将其路径到 Font 实例，并且他们也总是使用 Ortho Camera。我想知道 SpriteBatch 和字体绘制功能是否适用于 PerspectiveCamera。

Answer 1

好吧，我解决了：

简答：

SpriteBatch 在内部使用 OrthogonalPerspective。如果您使用 PerspectiveCamera，您需要将自定义视图矩阵传递给 SpriteBatch。你可以在 resize(...) 方法中做到这一点：

@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);
}

然后就不需要对精灵的投影矩阵做任何其他事情了（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);
    //...

长答案：因为我的最终目标是能够使用 SpriteBatch 来绘制文本，而通过上述对我的代码的修改，我可以做到这一点，因为精灵上的文本和网格都具有纹理现在可见，我注意到如果我没有为网格的顶点指定颜色，则所述顶点将获得我用于文本的颜色。换句话说，使用这样声明的纹理网格：

 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(...) 方法中也有这段代码会使网格变成红色：

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

解决此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});