PAGE 14

PAN, TILT, EXPOSURE & ZOOM

The camera position settings we looked at in page 13 were the equivalent of moving the camera and its tripod to a different position, or raising and lowering the tripod height. The settings we are going to examine now, the three Camera Orientation values, are the equivalent of using the pan and tilt lever on the tripod. The tripod is not moved and the height of the camera is unchanged, but the direction the lens is pointing, whether the camera is leaning back or forward, or whether the horizon tilts, can all be controlled by the pan and tilt lever.

The first parameter, the camera head position, controls the panning of the camera. It is calculated in degrees, and if you wish to move the camera to the left, and use a minus figure, the program will often, though not always, recalculate that to the equivalent positive degree figure.

The pan facility can be particularly useful if you wish to produce a panoramic picture from a viewpoint. If the viewpoint is near the centre of the terrain, and the distance to the target point is kept short, you can render four images with a 90 degree separation between each, and produce a complete panorama. Our snow and sea scene is not well suited to that because the camera position is down in one corner. I have therefore produced three overlapping pictures, at camera head position -64.9, -14.9 (the original) and 20. The last was really too near to the side of the terrain and so the horizon slopes in an unnatural way in the third image, because the area being viewed at the right is off the terrain. But I have been able to stitch them together sufficiently well for you to see what could be achieved with a carefully chosen terrain and camera position.

 head position -64.9  head position -14.9  head position 20
stitched view

The pitch value controls whether the camera is being pointed up or down. Pitch 0 is level. A plus figure means the camera is being tilted back and the lens pointed towards the sky. A minus figure means it is being tilted downwards towards the earth. Be careful about using too high a plus figure, because tilting the camera back means that more sky is included in the picture. If the sky covers too much of the picture area, the render may stop with an overflow error. Because of this it is better to increase the tilt a little at a time and do low-res renders until you get the effect you require, rather than go for a big increase which will probably overdo the effect you are looking for, and may cause Terragen to close down with an error message. Changing the pitch also affects the target position. When the camera is tilted, it is no longer focussing on a spot exactly the same distance from its position, and this is reflected in the target position co-ordinates, the major change being in the z(alt) co-ordinate because the tilt changes dramatically the height of the focus point. The table below shows the effect of pitch 10 and pitch -10 on both the scene, and the target position co-ordinates.

Pitch 0
x=167, y=141, z=3.06
Pitch 10
x=178.641, y=97.248, z=23.331
Pitch -10
x=178.904, y=96.256, z=-0.674
control pitch 0 pitch 10 pitch -10

The bank figure controls the left and right tilt of the camera, and will cause the horizon to slope when it moves from 0. Again there is an effect on the target positions co-ordinates, but they are not nearly so much affected as by pitch. A minus figure tilts the camera down to the right, and a plus figure down to the left.

Bank 0
x=167, y=141, z=3.06
Bank -5
x=167.602, y=138.739, z=3.209
Bank 10
x=167.75, y=138.181,z=3.281
control bank 0 bank right -5 bank left 10

Exposure and zoom settings can be changed from the render control panel, using the two sliders, but you can exercise more precise control over both, and access other options, if you click the camera settings button. At the time of writing the lens flare is not yet implemented, so we are considering only the features on the left of the settings panel.

Throughout this tutorial I am using the photochemical film setting, because that gives the most realistic and natural looking scenes. Below is a comparison between the two settings.

Photochemical Camcorder
photochemical camcorder
The exposure setting is just like that on a normal camera. Raising the exposure from its default setting of 1.414 makes the picture much lighter, while lowering the figure darkens it. In the table below I show settings at exaggerated values. Normally you would only need to adjust them very slightly.

Exposure = 1.414 Exposure = 5.028 Exposure = 0.47
normal over exposed  under exposed

wide angletelephotoThe range of focal lengths in the Terragen camera is huge. At its widest angle - zoom .25, left, it is virtually a fish-eye lens. This picture exposes the gap at the horizon between sky and sea, which will be dealt with in the next section of the tutorial when we come to look at generating sky and clouds.

On the right is the maximum zoom, 32. This enlarges, with full detail, the very centre of our picture. It is not easy to see on the original where this is, but if you look in the centre of the left hand picture of the exposure examples above, there is a point where the front range of hills dips down and you can see a faint brownish smudge between the two ranges. This telephoto picture reveals that the smudge is a strip of sea between the two ranges.

High magnification makes for very long render times, because although only a small portion of the whole picture is visible in the render window, the calculations have to be made for the whole picture. There is a long wait before anything appears in the window, and another long wait after it appears to be complete, before the render complete message is displayed.

With both exposure and zoom, the R buttons reset to the default value of 1.414.

Now I am going to apply some of the camera settings to the picture I am building up, to make it more attractive. Two things in particular I dislike about our scene so far. The foreground is too angular and intrudes into the scene too much, and in the bottom right corner of the picture you can see down the right hand side of the hill to where the sea comes up to it on that side. Although our terrain shows that this is a peninsula, I want to give the impression that this is a coastal bay and everything on the right is land. Below are the two render control panels, showing the changes I made. The camera position was moved forward and to the left, to get away from the angular intrusion in the foreground. The camera head was moved a little to the left, to bring the end of the range of hills better into the picture and to move away from the view down the right of the hill on the right. The pitch and camera position z co-ordinate were adjusted till exactly the right amount of foreground was visible. I also widened the lens angle from the default of 1.414 to 1.275 to include a little more in the scene. All this brought the sun away from the edge of the picture, so I moved it to the left a little, which also had the effect of improving the shadow angles on the sea.

original settings new settings

Below is a rendering of the picture, which is now almost finished. In the next section we shall look at generating skies and clouds, and try to produce one that suits the scene, instead of just taking whatever the cloud generator produces as we have so far.

scene 14

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