Function getProjectionMatrixCV

examples/helper/STG/graphics_utils.py:113–161

cx and cy range is -0.5 to 0.5 we use cx cy range -0.5 * 0.5

(znear, zfar, fovX, fovY, cx=0.0, cy=0.0)

#     return P

def getProjectionMatrixCV(znear, zfar, fovX, fovY, cx=0.0, cy=0.0):
    '''
    cx and cy range is -0.5 to 0.5  
    we use cx cy range -0.5 * 0.5
    
    '''
    tanHalfFovY = math.tan(fovY / 2)
    tanHalfFovX = math.tan(fovX / 2)

    top = tanHalfFovY * znear
    bottom = -top
    right = tanHalfFovX * znear
    left = -right

    # Adjust for off-center projection
    deltax = (2 * tanHalfFovX * znear) * cx  # 
    deltay = (2 * tanHalfFovY * znear) * cy  #
    
    left += deltax
    right += deltax
    top += deltay
    bottom += deltay


    # left -= deltax
    # right -= deltax
    # top -= deltay
    # bottom -= deltay


    # left = left(1 +cx)* znear
    # right += cx * znear
    # top += cy * znear
    # bottom += cy * znear

    P = torch.zeros(4, 4)

    z_sign = 1.0

    P[0, 0] = 2.0 * znear / (right - left)
    P[1, 1] = 2.0 * znear / (top - bottom)
    P[0, 2] = (right + left) / (right - left)
    P[1, 2] = (top + bottom) / (top - bottom)
    P[3, 2] = z_sign
#    P[2, 2] = z_sign * zfar / (zfar - znear)
    P[2, 2] = z_sign * (zfar+znear) / (zfar - znear)

    P[2, 3] = -(zfar * znear) / (zfar - znear)
    return P