Question

我正在尝试了解顶点缓冲对象。我已经能够在2D空间中成功渲染四边形（在初始化期间使用glOrtho），但在使用gluPerspective渲染时使用VBO时遇到问题。

我正在使用Java和LWJGL并在下面添加了我的代码。目前，只有黑色清晰呈现在窗户上。

public class GameWindow {
    // Height and width of the viewport
    private final int WIDTH = 800;
    private final int HEIGHT = 600;

    private final float zNear = 1f;
    private final float zFar = 1000f;

    long lastFrame, lastFps;
    int fps;

    public void start() {
        try {
            Display.setDisplayMode(new DisplayMode(WIDTH, HEIGHT));
            Display.create();
        } catch (LWJGLException e) {
            e.printStackTrace();
        }
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        gluPerspective(90, WIDTH / HEIGHT, zNear, zFar);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        float[] quadCoords = {
                100, 100, -1,
                300, 100, -1,
                300, 300, -1,
                100, 300, -1
        };

        float[] colorCoords = {
                1, 0, 0,
                0, 1, 0,
                0, 0, 1,
                1, 0, 1
        };

        FloatBuffer vertexData = BufferUtils.createFloatBuffer(4 * 3);
        vertexData.put(quadCoords);
        vertexData.flip();

        FloatBuffer colorData = BufferUtils.createFloatBuffer(4 * 3);
        colorData.put(colorCoords);
        colorData.flip();

        int vboVertex = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, vboVertex);
        glBufferData(GL_ARRAY_BUFFER, vertexData, GL_STATIC_DRAW);
        glBindBuffer(GL_ARRAY_BUFFER, 0);

        int vboColor = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, vboColor);
        glBufferData(GL_ARRAY_BUFFER, colorData, GL_STATIC_DRAW);
        glBindBuffer(GL_ARRAY_BUFFER, 0);

        getDelta();
        lastFps = TimeUtil.getTime();

        while (!Display.isCloseRequested()) {
            int delta = getDelta();
            updateFPS();
            glClear(GL_COLOR_BUFFER_BIT);

            glBindBuffer(GL_ARRAY_BUFFER, vboVertex);
            glVertexPointer(3, GL_FLOAT, 0, 0L);

            glBindBuffer(GL_ARRAY_BUFFER, vboColor);
            glColorPointer(3, GL_FLOAT, 0, 0L);

            glEnableClientState(GL_VERTEX_ARRAY);
            glEnableClientState(GL_COLOR_ARRAY);
            glDrawArrays(GL_QUADS, 0, 4);
            glDisableClientState(GL_COLOR_ARRAY);
            glDisableClientState(GL_VERTEX_ARRAY);

            Display.update();
            Display.sync(60);
        }
        Display.destroy();
    }

    private int getDelta() {
        long time = TimeUtil.getTime();
        int delta = (int) (time - lastFrame);
        lastFrame = time;

        return delta;
    }

    public void updateFPS() {
        if (TimeUtil.getTime() - lastFps > 1000) {
            Display.setTitle("FPS: " + fps);
            fps = 0;
            lastFps += 1000;
        }
        fps++;
    }

    public static void main(String[] args) {
        GameWindow window = new GameWindow();
        window.start();
    }
}

Answer 1

我认为你的四边形顶点不在视野范围内。如果没有设置视图矩阵（例如，通过gluLookAt），摄像机将指向-Z轴。您要求zNear和zFar为1.0和1000.0，因此将绘制z坐标-1.0和-1000.0之间的所有内容（zNear和zFar类似于相机的“距离”）。您还必须考虑到透视投影与正字法有很大不同。我会说，尝试将你的顶点移回Z轴，如下所示：

float[] quadCoords = {
        100, 100, -500,
        300, 100, -500,
        300, 300, -500,
        100, 300, -500
};

Answer 2

您的近剪裁平面为1，但渲染所有z坐标为-1

使用带有gluPerspective的顶点缓冲区对象

2 个答案: