by Mike McNamee Published 01/10/2015
Achieving Control of Your Control Points
When a montage element of an image has to be scaled, Ctrl-T is the shortcut and this reveals the 'handles' and 'control' points around the element. Most people never move the control point but it is in fact a powerful weapon when scaling. To move the control point you simply click and hold on it and then move it to a new position, which may be inside the transform bounding box or anywhere outside it also. Any transforms are then centred around the control point.
In the first screen grab the handles are shown, along with the control point. In the second screen grab the control point has been moved to the horizon line and when the Alt and Shift keys are held down, our model is scaled down the perspective cone towards the horizon - simples! As a matter of course, note that rotation also occurs centred on the control point as shown in the third screen grab. This rotation (indeed any transform) can be accomplished with great accuracy if the numerical values in the top menu bar are tweaked (by 1/100th of a degree if need be!).
Shadows are more difficult to make accurately although you can always pretend the light was soft and make a big fuzzy splodge! Computation of shadow shape can be done by geometry, using the horizon line as a reference again but, as the diagram shows, it is very complex even for a simple shape such as a sphere. Most ordinary mortals would set up a light and sphere and copy it! Shadows are vital in 'grounding' an element and by changing the placement of a simple shadow you can make a person stand firmly in contact with the ground or be up in the air. One way is to make a model of the element and study how it casts a shadow in the chosen lighting conditions and direction.
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