21 September 2009

Assignment #2









This one was quite impressive. A lot of complexity, 95% of which was dealt with correctly. I think I gave it an "A."

But I have to point out that there is a mistake in plotting the shadow of the notched awning. That the shadow of that awning keeps angling all the way down the front of the building is incorrect. This would only happen if the sun were directly above the VP or nearly so. (It's not really a good idea to place the sun even this near the VP--we'll see why in a minute).

One way to deal with the shadow of the awning is to find the plan of the forward corners of the awning on the sidewalk and make sure that, where the d-lines hit the wall, they go straight up. This is the method I've emphasized in class, because it always works.

I attach a second piece of art--the grayer, close-up one--that shows another way. This time the d-lines are on the vertical surfaces. To make this work we need to establish an elevation of sunlight, at the height of the sun, directly above the VP. This will be the source of the d-lines. The thinner of the two blue d-lines is for the surface of the double doors only. Because the sun is so close to the VP, the light makes a very shallow angle across the door. Look, for instance, at the very darkest cast shadow on the door. That is the shadow caused just by the building’s face being a few inches forward of the doors! Yet it falls more than halfway to the left side of the door, meaning most of the entire doorway is in cast shadow. If this sort of surprisingly long shadow is not for you, then place your sun (or SVP) farther from the VP than in this example. (Notice the artist failed to reckon this accurately in the next doorway, which should have been about the same.)

The a-line and the bolder d-line show how I found the shadow of the lower front right corner of the awning on the building's face (yellow dot). To the left of that point, I made a Law-of-Parallels line coming from the VP. This is what was missing from the student's original version.

(The Plan of Sunlight being so close to the VP makes the shadow of the awning fall much farther down the door than the face of the building.  Give a shadow farther to fall and it will, especially when it comes coasting in at a shallow angle like this)

Note: If you were to turn the drawing ninety degrees counter-clockwise, and essentially make the faces of the left buildings horizontal, the green line with the three green dots on it (which shows the clearance that the front of the awning has from the surface of the double door) could be viewed as the upright-stick-in-the-ground that was the first archetype I showed you re shadow plotting. With the drawing thus reoriented, the d-lines are running on "horizontal" surfaces as in that archetypal image.


JH

2 comments:

SarBear said...

Kristin and Sarahs minds are blown. @_@ This is quite complicated shadow mapping.

Bink MMX said...

I wish I knew a way of simplifying it!