android - (OpenGL ES) 远离 View 中心的对象被拉伸(stretch)

Question

所以我在 OpenGL ES 中生成了一个球体(具体来说，OpenGL ES 2.0，在 Java 中，适用于 Android)。当这个球体放置在与用于我的 View 矩阵的中心相同的位置时，它很好，但是当偏离中心时，球体会严重扭曲(见下文)。

为什么会发生这种情况，我该如何阻止它？

那是同一个球体。右上角的只是翻译成 x 和 y(不是 z)。

我实现 GLSurfaceView.renderer 的一些代码 fragment ，

public void onSurfaceCreated(GL10 unused, EGLConfig config) {
    GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    GLES20.glEnable(GLES20.GL_CULL_FACE);
    GLES20.glEnable(GLES20.GL_DEPTH_TEST);

    // Both centred on (0,0,0), of radius 1.0.
    outerSphere = new Sphere();
    centreSphere = new Sphere();
}

public void onSurfaceChanged(GL10 unused, int width, int height) {
    GLES20.glViewport(0, 0, width, height);

    ratio = (float) width / height;

    final float left = -ratio;
    final float right = ratio;
    final float bottom = -1.0f;
    final float top = 1.0f;
    final float near = 1.0f;
    final float far = 100.0f;

    Matrix.frustumM(projMatrix, 0, left, right, bottom, top, near, far);
}

public void onDrawFrame(GL10 unused) {
    GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);

    float eyeX = 0.0f;
    float eyeY = 0.0f;
    float eyeZ = 10.0f;

    final float lookX = 0.0f;
    final float lookY = 0.0f;
    final float lookZ = 0.0f;

    final float upX = 0.0f;
    final float upY = 1.0f;
    final float upZ = 0.0f;

    Matrix.setLookAtM(viewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ,
                      upX, upY, upZ);

    // Set identity matrix as input for translations.
    Matrix.setIdentityM(outerModelMatrix, 0);

    // Translate outer sphere by 5 in x and y.
    Matrix.translateM(outerModelMatrix, 0, 5.0f, 5.0f, 0.0f);

    // MVP matrix = Projection * View * Model.
    Matrix.multiplyMM(centreMVPMatrix, 0, viewMatrix, 0, centreModelMatrix, 0);
    Matrix.multiplyMM(centreMVPMatrix, 0, projectionMatrix, 0, centreMVPMatrix, 0);
    Matrix.multiplyMM(outerMVPMatrix, 0, viewMatrix, 0, outerModelMatrix, 0);
    Matrix.multiplyMM(outerMVPMatrix, 0, projectionMatrix, 0, outerMVPMatrix, 0);

    outerSphere.draw(outerMVPMatrix);
    centreSphere.draw(outerMVPMatrix);

}

我的着色器很简单，

private final static String vertexShaderCode =
    "uniform mat4 u_MVPMatrix;" +
    "attribute vec4 a_Position;" +
    "uniform vec4 u_Color;" +
    "void main() {" +
    "    gl_Position = u_MVPMatrix * a_Position;" +
    "}";
private final static String fragmentShaderCode = 
    "precision mediump float;" +
    "uniform vec4 u_Color;" +
    "void main() {" +
    "    gl_FragColor = u_Color;" +
    "}";

我几乎省略了 Sphere 类的所有代码，以及其他我认为不需要的东西(？)，但如果需要它们，我会把它们放上去。

Answer 1

欢迎来到 perspective distortion 的世界!

更多细节:您的视野太窄，您必须调整平截头体的形状，使其更大一些。