8
Using the Horizon to Match Perspective 1225
Usi ng the H ori zon to M a tch
Per specti ve
Thehorizonofasceneistheedgeofvisionat
the heig ht of the camera, paral lel with the world
coordinate plane. You can view the horizon in
camera view por ts.
Horizon line displayed in a c amera viewport
A camera is level when it and its target are the
same height from the world coordinate plane. In
other words, the camera’s local Z axis is parallel
to the world plane. When the camera is level, the
horizonlineiscenteredintheviewport.Asthe
camera ti lts up, the horizon line lowers; as it tilts
down, the horizon line raises.
The horizon line control is in the camera’s
Parameters rollout (page 2–1218)
.
The horizon line can help you match the
perspective of your scene to the p erspective of
a still image. In general, matching perspective
involves the follow i ng steps:
1. Display the horizon line. Use it to help you
adjust the camera and target so they are level.
2. Display the image in the camera viewport. Use
Views > Viewport Background and choose
Files in the Background Source group.
If the image’s horizon and the camera horizon
don’t match, you have to offset the image,
perhaps by using a paint program.
3. Use
Orbit (page 3–791)
to move the
camera until the perspective of the scene
roughly matches that of the still image.
4. Adjust the camera ’s
perspective (page
3–789)
to fine-tune the perspective match.
5. Use
Move (page 1–419)
with the c amera
or target to position the scene against the
background.
If you raise or lower the camera, raise or lower
the t arget by an equal amount, in order to keep
them level and m aintain the horizon.
Yo u c a n a l s o u s e t h e
Camera Match utility
(page 2–1232)
to match the perspective of a
camera to a photo g r aph. You w ill need accurate
scenemeasurementstodoso.
Animating Cameras
Youanimateacamerabyusingtransformsor
changing its creation parameters in different
key frames while the Set Key or Auto Key button is
on. The program interpolates camera transforms
and parameter values between key frames, as it
does for object geometry.
See
Auto Key Animation Mode (page 3–760)
and
Track View (page 2–483)
for further descriptions
of animation. This topic summarizes some
possibilities and sug gests some techniques.
In general, it’s best to use a
free camera (page
2–1215)
when the camera is to move within the
scene; use a
target camera (page 2–1216)
when
camera position is fixed.