Positioning the Eye and Look points

One of the problems I commonly note when people are learning to use Rayshade is that they tend to place their eye and look points badly. Often people put considerable effort into creation of the scene (or object) they are modelling and then try to guess an appropriate viewing position! The usual result is that a number of images need to be produced until the view is close to what is wanted.

There are a few simple things that can be done to aid this process: sketch out (to scale) a plan of the scene (onto grid paper or similar - I often use a ruled pad with a second sheet turned 90 degrees underneath).

Draw up an approximate cone of vision (on a separate sheet to your plan): if your eye and look points are at similar heights (that is, you are not looking down onto your scene) then draw a straight line to represent the viewing direction from the eye point to the look point; then draw, from one end of your line, lines out at an angle of about half your horizontal field of view. The point where the three lines join represents your eye point. If your eye point is to be significaantly higher than the point you're looking at (the lookp), then draw the lines of the cone of vision wider.

Figure 1-4
This diagram is a plan view of the five boxes example in this chapter, showing the horizontal field of view from the eye-point to the look-point.

These three lines now (approximately) represent your cone of vision! Place this under you sketched scene and move it around until the view enclosed between the outer lines (as "seen" from the point where the lines join) is about what you want.

Then note on your (plan) sketch the place where the lines join (the eye point!); to determine the look point follow your centre line until it gets to about the middle of your scene and use that position as the look point. The look point could, in fact, be anywhere along the centre line: you might place your look point beyond your object entirely, depending on the effect you are trying to achieve.

Figure 1-5
This diagram shows section along the "line" from the eye-point to the look-point, and a (rotated) plan.

Depending on the complexity of the scene it could also be prudent to draw a sketch section along the eye/look point line, to determine whether objects will be visible or will be obscured by other objects closer to the eye. Depending on your views on neat/clean sketches, this section could be drawn over the top of the previous sketch or on a separate sheet.


Go to next chapter: Rayshade Primitives - Blob.

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THE END - Notes on Rayshade - 1 - Introduction