Last time, we considered the method of showing a proper shadow cast from a light source which is behind the viewer.  This lesson today will demonstrate the opposite situation, where the light source is before the viewer.

Andrew Loomis in his book Successful Drawing shows us the method of solving how to draw shadows in proper perspective.  The first point which needs stating is a concept hinted at from 2 postings past, which I hope to make concrete by the end of this lesson.  The aforementioned idea is that if the light source is Behind, the angle of light is below the horizon.  When the light source is before the viewer, the angle of the light is above the horizon.  Hold onto this thought, and I will review it at the end of the lesson, where I am sure it will form an integration for you.

Here are the steps for casting a perspectival shadow from a light source which is before.

1. Set up your horizon and the object using proper perspective.  Establish the Vanishing Points for the object’s sides, and draw the appropriate angles.  Draw the guidelines for the perspective on a separate layer of vellum or digitally, then remove the guidelines when the object is perspective. Save the layer.
2. Since the light source in this exercise is before the viewer, it is proper to next establish the position of where that light is coming from specifically.  This should be done with precision within the layout phase of your drawing.  Even if the light is not going to be within the boundaries of your finish crop for the illustration, you must lay it out with exact placement, or else your shadows will appear unconvincing.  Drop a line vertically down at 90 degrees from the centre of the light source to the horizon line.
3. The point where the vertical line crosses the horizon will be the VP of the shadows. This is a crucial step, so pay close attention to it.  As a rule, the Vanishing Point of shadows is directly below the light source when the light is cast from a Before placement.  The blue lines below represent the projection for the  Shadow VP.  Please not that these guidelines cross through the corners of the object you are drawing, laying on the ground plane.   
4. Next we will cast the lines of light, which will fall like a triangle from the light source.  Each corner of the object you are drawing will interrupt the light, but the perspective you have chosen may conceal certain corners.  In this drawing there are 3 corners which will cast a shadow we can see, so there will be 3 lines.  If your object and perspective yields more corners which will cast a shadow, use the appropriate amount of lines.  Note how the light lines emanate from the centre of the light source, not its perimeter.  Cast the light lines further than where the Shadow VP lines lay on the plane.  
5. Now, turn on the layer with the original perspective lines showing.  These perspective lines will give us the other half of the information we ned  regarding where the shadow’s perimeter will lay.
6. Where the red light lines cross either the blue Shadow VP lines or the black object perspective lines with demarcate the corners of the cast shadow your object will make, given the perspective you have chosen, and the placement of the light source.  I have numbered these 1-4.  Numbers 5 and 6 are the points where your object touches the plane it rests on, and from these points the shadow will originate.
7.  Outline the cast shadow perimeter, then fill it in with the value appropriate for the light intensity you are describing.  The darker the shadow, the brighter the light.  Add half-tones to the shaded sides of the object (the sides facing away from the light) Flat planes have even shading, curving planes will appear as a gradation.  
8. Remove the guidelines to reveal your illustration of a properly done shadow, in perspective, with the light source before the viewer.  Congratulations!

As a last comment, think back the the idea of the angle of light above and below the horizon which I mentioned at the beginning.  If you think about it, it is natural to recognize that the angle will come from above when the light is before, because when standing on the earth, you perceive the horizon above you.  If the light is coming from behind, the angle must come from below for the same reason.  It is possible, tho rare that one’s point of view can be distorted, such that the horizon is perceived as below you.  This could occur if you are inverted or suspended in the air.  Such points of view will break this rule.  Luckily, there are limited calls for illustrations of that type.  I will cover such considerations at a much later date, due to their peculiarity.

There are many more subtleties related to cast shadows, but I believe I will go onto showing organic cast shadows in perspective next week.  It will be a difficult one!