Global light illumination and light effects in
Adobe Photoshop (part 2)
... continued from part 1
So letís see how we can emulate these 3D illumination effects from Photoshop. I remind you that light itself is invisible, what we really saw itís reflection or refraction when light
rays bounce on same object. So letís take a sphere on the floor of an empty room.
Assume that there is a global source light (like some large windows but not to be seen in this scene) also called ambient light, a main spotlight from the left, say upper left, and a second one, opposite with the first, defining what is known to be as the basic 3 point lighting. Usually the last two have opposite temperatures, for example orange (hot) for main, and blue (cold) for the second
The left spot is also called the key light, and the right one (from opposite) is called backlight or the rim light. First draw the sphere, color it whatever color you want (better use a dark one) and use Dodge Tool in order to give the left part of the sphere a specular light reflection. Highlight and 20-30% exposure are the proper parameters. Then to stress the contrast a little bit, use the Burn Tool to cast some shadow on the opposite part of the sphere. Now letís add some rim light; remember the rim light is the backlight coming from the opposite direction of main spotlight; its main goal is to enhance a little bit the darked edges opposed to main specular reflection; in a darken environment this edges may become invisible altering the 3D effect of the scene. So create a new layer, bring the selection of sphere on that layer, shrink it , say 1-2px, and with a large soft brush draw a white stroke of light.
Next you have to draw shadow; there is no help from Adobe Photoshop at this point. You should imagine the geometrical form of shadow, also how sharp or diffuse this is.
As a rule, if light source is a single point the shadow is clear sharp, and when light source has some 3D dimensions (as it happens in real world) there always will be some diffuse edges for shadow. (the phenomenon is called diffraction). So create a new layer
put it behind the sphere layer, draw geometrical shadow form, fill it with a dark gray, and give it some Gaussian blur.
For the ambient light create a new layer above the rest of layers and fill with the ambiental color you want (white for daylight, red-orange for sunsets). Set the blend mode to Soft light and decrease its opacity at 50-60%. You can go even further and instead filling the ambient light layer with unique color, render some difference clouds (now main spotlight may become visible !) and give it the ambient color and transparency you wish. This way you ca simulate some foggy environment, just good enough to enhance the 3D effect of your scene.
May, 12, 2009