|
This task shows you how to add a visual effect making objects that are not
in focus (i.e. located far from the camera target) appear blurry, thus
giving a sense of depth to the image. |
|
Depth of field can be used with perspective
cameras/viewpoints only. Depth of field and glow effects work
independently from each other.
|
|
Open the
SceneEffects.CATProduct document. |
|
-
Click
Create Shooting
to open the Shooting Definition dialog box then select the
Effects tab:
-
Click Active to activate the
depth of field.
As soon as the option is selected, the
Confusion radius box is activated and the preview displayed
to the right is updated: |
|
As you already know it, ray tracing is a rendering
technique that computes the color for a given pixel by sending 1
ray from the camera into the scene.
In case of depth of field effect, 4 rays are sent for each given
pixel and the 4 resulting colors are then used to compute an
average value, thus creating a blurring effect.
Let's have a look at the schema below illustrating depth of field:
|
|
The focus plane is a fictive plane
perpendicular to the camera axis (the view direction) whose origin
is located at the camera target. The focus plane represents the
"sharpness plane", i.e. the distance at which objects appear clear
in outline.
The red line corresponds to a ray sent without any effect whereas
the green lines correspond to rays sent for a depth of field
effect.
The blue dot is the pixel in the rendered image (identified by its
row and column coordinates) whose color will be determined by the
ray (rays in case of depth of field) cast from the camera. |
-
Use the
Confusion radius box to specify the radius of the camera
origin from which rays are sent.
You can enter values comprised between 1 and 10
millimeters and check the result in the preview displayed to the
right. The smallest the radius, the sharpest the result. |
If the
result is not satisfactory despite a small radius, you can access
the Quality tab in the Shooting Definition
dialog box and increase the
accuracy. However, bear in mind that the more rays, the longer
the processing time. |
-
Click OK to validate.
|
|
You are
now ready to render the shooting by clicking Render Shooting
(you can also right-click the Shooting item in the specification tree
then select Render Single Frame).
The following are samples
illustrating the various results you can obtain:
|