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<strong class="NavBar">POV-Ray 3.6 for UNIX documentation</strong><br> <strong>2.2.6
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<h3><a name="s02_02_06">2.2.6 </a>Using the Camera</h3>
<a name="s02_02_06_i1">
<h4><a name="s02_02_06_01">2.2.6.1 </a>Using Focal Blur</h4>
<a name="s02_02_06_01_i1"><a name="s02_02_06_01_i2">
<p>
Let's construct a simple scene to illustrate the use of focal blur. For this example we will use a pink sphere, a
green box and a blue cylinder with the sphere placed in the foreground, the box in the center and the cylinder in the
background. A checkered floor for perspective and a couple of light sources will complete the scene. We create a new
file called <code> focaldem.pov</code> and enter the following text
</p>
<pre>
#include "colors.inc"
#include "shapes.inc"
#include "textures.inc"
sphere {
<1, 0, -6>, 0.5
finish {
ambient 0.1
diffuse 0.6
}
pigment { NeonPink }
}
box {
<-1, -1, -1>, < 1, 1, 1>
rotate <0, -20, 0>
finish {
ambient 0.1
diffuse 0.6
}
pigment { Green }
}
cylinder {
<-6, 6, 30>, <-6, -1, 30>, 3
finish {
ambient 0.1
diffuse 0.6
}
pigment {NeonBlue}
}
plane {
y, -1.0
pigment {
checker color Gray65 color Gray30
}
}
light_source { <5, 30, -30> color White }
light_source { <-5, 30, -30> color White }
</pre>
<p>
Now we can proceed to place our focal blur camera to an appropriate viewing position. Straight back from our three
objects will yield a nice view. Adjusting the focal point will move the point of focus anywhere in the scene. We just
add the following lines to the file:
</p>
<pre>
camera {
location <0.0, 1.0, -10.0>
look_at <0.0, 1.0, 0.0>
// focal_point <-6, 1, 30> // blue cylinder in focus
// focal_point < 0, 1, 0> // green box in focus
focal_point < 1, 1, -6> // pink sphere in focus
aperture 0.4 // a nice compromise
// aperture 0.05 // almost everything is in focus
// aperture 1.5 // much blurring
// blur_samples 4 // fewer samples, faster to render
blur_samples 20 // more samples, higher quality image
}
</pre>
<p>
The focal point is simply the point at which the focus of the camera is at its sharpest. We position this point in
our scene and assign a value to the aperture to adjust how close or how far away we want the focal blur to occur from
the focused area.
</p>
<p>
The aperture setting can be considered an <em>area of focus</em>. Opening up the aperture has the effect of making
the area of focus smaller while giving the aperture a smaller value makes the area of focus larger. This is how we
control where focal blur begins to occur around the focal point.
</p>
<p>
The blur samples setting determines how many rays are used to sample each pixel. Basically, the more rays that are
used the higher the quality of the resultant image, but consequently the longer it takes to render. Each scene is
different so we have to experiment. This tutorial has examples of 4 and 20 samples but we can use more for high
resolution images. We should not use more samples than is necessary to achieve the desired quality - more samples take
more time to render. The confidence and variance settings are covered in section "<a href="s_100.html#s03_03_01_03">Focal
Blur</a>".
</p>
<p>
We experiment with the focal point, aperture, and blur sample settings. The scene has lines with other values that
we can try by commenting out the default line with double slash marks and un-commenting the line we wish to try out.
We make only one change at a time to see the effect on the scene.
</p>
<p>
Two final points when tracing a scene using a focal blur camera. We need not specify anti-aliasing because the
focal blur code uses its own sampling method that automatically takes care of anti-aliasing. Focal blur can only be
used with the perspective camera.
</p>
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<strong>2.2.6 Using the Camera</strong>
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