最近在研究 【高通 AR 】技术，通过其Examples来学习相关SDK。
在研究 ImageTagets 的时候，想获取：
1、目标空间对应的3D point 对应的 屏幕上2D point ；
2、屏幕上触碰一点 对应的 空间坐标。
虽然其开发文档
：
https://developer.vuforia.com/resources/dev-guide/screen-coordinates
对这2个需求进行了实现方式阐述，但是都不是很具体。所以花了不少时间去实现（尤其是需求1）。现将 空间坐标 转换成 屏幕坐标的方法总结如下：
Target space to screen space
//xq
- (CGPoint)getScreenPointByPose:(QCAR::Matrix34F)pose
{
// need to account for the orientation on view size
CGFloat viewWidth = self.frame.size.height; // Portrait
CGFloat viewHeight = self.frame.size.width; // Portrait
UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
if (UIInterfaceOrientationIsLandscape(orientation))
{
viewWidth = self.frame.size.width;
viewHeight = self.frame.size.height;
}
// calculate any mismatch of screen to video size
QCAR::CameraDevice& cameraDevice = QCAR::CameraDevice::getInstance();
const QCAR::CameraCalibration& cameraCalibration = cameraDevice.getCameraCalibration();
QCAR::VideoMode videoMode = cameraDevice.getVideoMode(QCAR::CameraDevice::MODE_DEFAULT);
CGFloat scale = viewWidth/videoMode.mWidth;
if (videoMode.mHeight * scale < viewHeight)
scale = viewHeight/videoMode.mHeight;
CGFloat scaledWidth = videoMode.mWidth * scale;
CGFloat scaledHeight = videoMode.mHeight * scale;
CGPoint margin = {(scaledWidth - viewWidth)/2, (scaledHeight - viewHeight)/2};
CGPoint center =[self projectCoord:CGPointMake(0,0) inView:cameraCalibration andPose:pose withOffset:margin andScale:scale];
NSLog(@"center = %@",[NSValue valueWithCGPoint:center]);
CGPoint centerNew = center;
centerNew.x = viewHeight - center.y;
centerNew.y = center.x;
NSLog(@"centerNew = %@",[NSValue valueWithCGPoint:centerNew]);
return centerNew;
}
- (CGPoint) projectCoord:(CGPoint)coord inView:(const QCAR::CameraCalibration&)cameraCalibration andPose:(QCAR::Matrix34F)pose withOffset:(CGPoint)offset andScale:(CGFloat)scale
{
CGPoint converted;
QCAR::Vec3F vec(coord.x,coord.y,0);
QCAR::Vec2F sc = QCAR::Tool::projectPoint(cameraCalibration, pose, vec);
converted.x = sc.data[0]*scale - offset.x;
converted.y = sc.data[1]*scale - offset.y;
return converted;
}
其中：方法一中传入参数
pose
由
– (
void
)renderFrameQCAR
方法获取，即被跟踪到目标的 3*4姿态矩阵。（详见
：
https://developer.vuforia.com/resources/dev-guide/pose-matrix-explained
）
，返回值 centerNew 即为 屏幕上对应的坐标。
版权声明：本文为wwmusic原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。