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View Full Version : rotation of relative object in perspective? (hand drawn)

unsped
12-15-2008, 05:10 PM
im a big fan of scott robertson's concept art, i have a question regarding rendering objects that are rotated in 2-3 point perspective.

most of the video's/tutorial's show object/vehicle creation where the item is lined up along a vanishing point. how do you go about rending an item that is rotated from your initial vp's?

my guess is that the items x and y axis define the vanishing points location along the horizon line, rotating the item along an axis moves its corresponding vanishing point.

would this mean that multiple items in a scene would have different vanishing points based on thier rotation compared to each other?

i'm assuming that the x and y vanishing points are stuck along the horizon, but how would you know where a new z (height) vanishing point would be in a 3 point system?
smackcakes
12-22-2008, 06:47 AM
Well I'm not a big expert on perspective drawing but the way I understand it there is really only 1 true vanishing point ala single point perspective. This actually represents the viewer in weird reversed sort of way. Because while objects appear to be converging at a single point in the distance what is really happening is light is converging towards a single point as it moves towards you. The single point being the pupil of your eye, which all the light has to fit through.

3D computer programs all use single point perspective, even when an object is rotated at an arbitrary angle. I believe 2 point perspective is really just a sort of ad hoc pseudo perspective for drawing boxes at an angle, because it's difficult for humans to deal with the rotation with only a single vanishing point. Obviously if you had a shape more complicated than a box, such as a dodecahedron then you would need many more vanishing points.

Different objects would need a unique vanishing point for every surface with a unique rotation. But all these points would have to be relative to the true vanishing point or it would look wrong.

My advice if you are drawing multiple complex shapes, would be to stick with single point perspective and draw every object in a bounding box. You can then use the box to correctly position each object, or even to find the pseudo vanishing points for a particular rotation.

I drew this as an example of some box shapes with different rotations using just a single point. Even though they are rotated differently they should still have the correct perspective relative to each other. If you traced a line from these boxes to where the pseudo vanishing points would be, you could then use those points to draw another box with the same rotation but a different size/shap or possition in the picture.

http://i103.photobucket.com/albums/m134/SmackCakes/xyzboxrot.jpg

I'm not entirely sure what you were asking about 3 point perspective, but 3 point perspective is really 4 point perspective. Left is to Right as UP is to Down so whatever you were doing for 2 point perspective, you can just rotate your paper 90 degrees and do the same thing for 3 and 4 point perspective.
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12-22-2008, 06:47 AM
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