ARCamera.projectPoint的快速实现
ARCamera.projectPoint的快速实现
提问于 2019-11-26 10:44:18
我正在尝试使用相机上的ARCamera.projectPoint和viewMatrix实现一个projectionMatrix函数。
要创建这样的东西：
let position = simd_float3(x: 1, y: 2, z: 3)
let position4 = simd_float4(x: position.x, y: position.y, z: position.z, w: 1)
let projectionMatrix = frame.camera.projectionMatrix(for: .landscapeRight, viewportSize: frame.camera.imageResolution, zNear: 0.001, zFar: 1000.0)
let viewMatrix = frame.camera.viewMatrix(for: .landscapeRight)
let projection = position4 * projectionMatrix * viewMatrix
let arkitProjection = frame.camera.projectPoint(position, orientation: .landscapeRight, viewportSize: frame.camera.imageResolution)
assert(projection.x == Float(arkitProjection.x))
assert(projection.y == Float(arkitProjection.y))但我不知道如何正确地实现它。希望你能帮忙。
回答 1
Stack Overflow用户
回答已采纳
发布于 2021-02-16 22:50:34
你离我很近！在projection中，实际上是一个“剪辑空间”位置(也注意到我固定了矩阵乘法的顺序)。然后，您需要使用“透视划分”将其转换为“规范化设备坐标”(在xyz维度中具有从-1到+1的坐标)。最后，您需要根据图像大小将其线性映射到图像中的位置。
let position = simd_float3(x: 1, y: 2, z: 3)
let position4 = simd_float4(x: position.x, y: position.y, z: position.z, w: 1)
let projectionMatrix = frame.camera.projectionMatrix(for: .landscapeRight, viewportSize: frame.camera.imageResolution, zNear: 0.001, zFar: 1000.0)
let viewMatrix = frame.camera.viewMatrix(for: .landscapeRight)
let clipSpacePosition = projectionMatrix * viewMatrix * position4
let normalizedDeviceCoordinate = clipSpacePosition / clipSpacePosition.w
let projection = CGPoint(
x: (CGFloat(normalizedDeviceCoordinate.x) + 1) * (frame.camera.imageResolution.width / CGFloat(2)),
y: ((-CGFloat(normalizedDeviceCoordinate.y) + 1)) * (frame.camera.imageResolution.height / CGFloat(2))
)
let arkitProjection = frame.camera.projectPoint(position, orientation: .landscapeRight, viewportSize: frame.camera.imageResolution)
assert(abs(projection.x - arkitProjection.x) < 0.01)
assert(abs(projection.y - arkitProjection.y) < 0.01)进一步读：
- http://www.opengl-tutorial.org/beginners-tutorials/tutorial-3-matrices/#the-projection-matrix (关于剪辑空间和projection)
- https://developer.apple.com/documentation/arkit/tracking_and_visualizing_faces的一般有用信息)(搜索“透视divide")
- https://learnopengl.com/Getting-started/Coordinate-Systems
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原文链接：
https://stackoverflow.com/questions/59049128
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