旋转OpenGL-ES对象

Question

经过几个小时的努力，我终于能够画出一个物体，但当它旋转时就卡住了。我正在尝试绕y轴旋转，但我似乎无法以任何方式使旋转平滑。它几乎是跳来跳去的。中间可能有一些不必要的东西，因此我使用了一个模板。

- (void)update
{
    float aspect = fabsf(self.view.bounds.size.width / self.view.bounds.size.height);
    GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 0.1f, 100.0f);

    self.effect.transform.projectionMatrix = projectionMatrix;

    GLKMatrix4 baseModelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -4.0f);

    // Compute the model view matrix for the object rendered with ES2
    GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, 0.0f);
    modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, startPoint.y, 0.0f, 1.0f, 0.0f);

    dx = dy = 0;
    modelViewMatrix = GLKMatrix4Multiply(baseModelViewMatrix, modelViewMatrix);

    _normalMatrix = GLKMatrix3InvertAndTranspose(GLKMatrix4GetMatrix3(modelViewMatrix), NULL);

    _modelViewProjectionMatrix = GLKMatrix4Multiply(projectionMatrix, modelViewMatrix);

    _rotation += self.timeSinceLastUpdate * 0.5f;
}

以及我的触摸行为：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    startPoint = [touch locationInView:self.view];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    CGPoint point = [touch locationInView:self.view];
    dx = point.y - startPoint.y;
    dy = point.x - startPoint.x;
    startPoint = point;
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{

}

提前谢谢。

Answer 1

通过下面的苹果图书馆链接，可以解决你的问题[http://developer.apple.com/library/ios/#samplecode/GLSprite/Introduction/Intro.html#//apple_ref/doc/uid/DTS40007325