dreamgaussian / cam_utils.py
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import numpy as np
from scipy.spatial.transform import Rotation as R
import torch
def dot(x, y):
if isinstance(x, np.ndarray):
return np.sum(x * y, -1, keepdims=True)
else:
return torch.sum(x * y, -1, keepdim=True)
def length(x, eps=1e-20):
if isinstance(x, np.ndarray):
return np.sqrt(np.maximum(np.sum(x * x, axis=-1, keepdims=True), eps))
else:
return torch.sqrt(torch.clamp(dot(x, x), min=eps))
def safe_normalize(x, eps=1e-20):
return x / length(x, eps)
def look_at(campos, target, opengl=True):
# campos: [N, 3], camera/eye position
# target: [N, 3], object to look at
# return: [N, 3, 3], rotation matrix
if not opengl:
# camera forward aligns with -z
forward_vector = safe_normalize(target - campos)
up_vector = np.array([0, 1, 0], dtype=np.float32)
right_vector = safe_normalize(np.cross(forward_vector, up_vector))
up_vector = safe_normalize(np.cross(right_vector, forward_vector))
else:
# camera forward aligns with +z
forward_vector = safe_normalize(campos - target)
up_vector = np.array([0, 1, 0], dtype=np.float32)
right_vector = safe_normalize(np.cross(up_vector, forward_vector))
up_vector = safe_normalize(np.cross(forward_vector, right_vector))
R = np.stack([right_vector, up_vector, forward_vector], axis=1)
return R
# elevation & azimuth to pose (cam2world) matrix
def orbit_camera(elevation, azimuth, radius=1, is_degree=True, target=None, opengl=True):
# radius: scalar
# elevation: scalar, in (-90, 90), from +y to -y is (-90, 90)
# azimuth: scalar, in (-180, 180), from +z to +x is (0, 90)
# return: [4, 4], camera pose matrix
if is_degree:
elevation = np.deg2rad(elevation)
azimuth = np.deg2rad(azimuth)
x = radius * np.cos(elevation) * np.sin(azimuth)
y = - radius * np.sin(elevation)
z = radius * np.cos(elevation) * np.cos(azimuth)
if target is None:
target = np.zeros([3], dtype=np.float32)
campos = np.array([x, y, z]) + target # [3]
T = np.eye(4, dtype=np.float32)
T[:3, :3] = look_at(campos, target, opengl)
T[:3, 3] = campos
return T
class OrbitCamera:
def __init__(self, W, H, r=2, fovy=60, near=0.01, far=100):
self.W = W
self.H = H
self.radius = r # camera distance from center
self.fovy = np.deg2rad(fovy) # deg 2 rad
self.near = near
self.far = far
self.center = np.array([0, 0, 0], dtype=np.float32) # look at this point
self.rot = R.from_matrix(np.eye(3))
self.up = np.array([0, 1, 0], dtype=np.float32) # need to be normalized!
@property
def fovx(self):
return 2 * np.arctan(np.tan(self.fovy / 2) * self.W / self.H)
@property
def campos(self):
return self.pose[:3, 3]
# pose (c2w)
@property
def pose(self):
# first move camera to radius
res = np.eye(4, dtype=np.float32)
res[2, 3] = self.radius # opengl convention...
# rotate
rot = np.eye(4, dtype=np.float32)
rot[:3, :3] = self.rot.as_matrix()
res = rot @ res
# translate
res[:3, 3] -= self.center
return res
# view (w2c)
@property
def view(self):
return np.linalg.inv(self.pose)
# projection (perspective)
@property
def perspective(self):
y = np.tan(self.fovy / 2)
aspect = self.W / self.H
return np.array(
[
[1 / (y * aspect), 0, 0, 0],
[0, -1 / y, 0, 0],
[
0,
0,
-(self.far + self.near) / (self.far - self.near),
-(2 * self.far * self.near) / (self.far - self.near),
],
[0, 0, -1, 0],
],
dtype=np.float32,
)
# intrinsics
@property
def intrinsics(self):
focal = self.H / (2 * np.tan(self.fovy / 2))
return np.array([focal, focal, self.W // 2, self.H // 2], dtype=np.float32)
@property
def mvp(self):
return self.perspective @ np.linalg.inv(self.pose) # [4, 4]
def orbit(self, dx, dy):
# rotate along camera up/side axis!
side = self.rot.as_matrix()[:3, 0]
rotvec_x = self.up * np.radians(-0.05 * dx)
rotvec_y = side * np.radians(-0.05 * dy)
self.rot = R.from_rotvec(rotvec_x) * R.from_rotvec(rotvec_y) * self.rot
def scale(self, delta):
self.radius *= 1.1 ** (-delta)
def pan(self, dx, dy, dz=0):
# pan in camera coordinate system (careful on the sensitivity!)
self.center += 0.0005 * self.rot.as_matrix()[:3, :3] @ np.array([-dx, -dy, dz])