3d Transformations - Revision history

ClayOgre: /* Shear */

2010-11-06T01:17:20Z

Shear

← Older revision		Revision as of 01:17, 6 November 2010
Line 36:		Line 36:
	=Shear=		=Shear=

	Shearing is "a deformation of an object in which parallel planes remain parallel but are shifted in a direction parallel to themselves." If you don't understand, look at the image below. The three values after shear-keyword define a vector. Vectors ~~lenght~~ represents change per Z-axis unit. If you have 10 ~~units~~ high meshbox, and shear it by 1 0 0, top will move 10 * 1 away from the bottom in X-axis direction. In next example, we use shear to make an escalator with nice ends.		Shearing is "a deformation of an object in which parallel planes remain parallel but are shifted in a direction parallel to themselves." If you don't understand, look at the image below. The three values after shear-keyword define a vector. Vectors length represents change per Z-axis unit. If you have 10 unit high meshbox, and shear it by 1 0 0, top will move 10 * 1 away from the bottom in X-axis direction. In next example, we use shear to make an escalator with nice ends.

ClayOgre: /* Shift */

2010-11-06T01:16:26Z

Shift

← Older revision		Revision as of 01:16, 6 November 2010
Line 31:		Line 31:

	Shifting means moving the object. It is used in same manner as old position-keyword. Without position-keyword, object is placed around 0 0 0. When shift moves it from origin, coordinates are just like with position. However, shift is repeatable, and sequential moves will use last point as origin.		Shifting means moving the object. It is used in same manner as old position-keyword. Without position-keyword, object is placed around 0 0 0. When shift moves it from origin, coordinates are just like with position. However, shift is repeatable, and sequential moves will use last point as origin.

	[[Image:shift.png\|alt text]]		[[Image:shift.png\|alt text]]

Optic Delusion: Copy JPA's 3-d trandormations page from http://kapsi.fi/~jpa/stuff/bzw/ ©Petteri Aimonen 2005 Used by permission

2007-12-28T00:36:59Z

New page

The following is ©Petteri Aimonen 2005, Used by permission.

=Introduction=
In version 1.10.8 and older bzflag, objects position, rotation and size where defined by, logically, position, rotation and size keywords. When 2.0 introduced 3d rotation, this had to change. Position and rotation have been obsoleted by their superiors, shift and spin. Size could be replaced with scale, but there is no need for that on traditional objects (mesh are a bit different). All keywords are order-specific. If you do shift before spin, it will still spin the object around 0 0 0, moving it somewhere else than where it was meant to be.

box
position 50 100 0
size 20 20 5
rotation 45
end

can now be written:

meshbox
size 20 20 5
spin 45 0 0 1
shift 50 100 0
end

=Spin=

Spin can be used to rotate object around a specific axis. Axis is a line, defined by two points. First value after spin-keyword is rotation in degrees. The other three values determine which axis the spin will be applied. It is usually simple to think rotation around the standard axises. You can spin around any axis, diagonal or anything. Anyway, all rotations can be made by rotating around standard axises, and they are usually most simple to think of.

X-axis eg. spin 45 1 0 0
Y-axis eg. spin 45 0 1 0
Z-axis, normal rotation, eg. spin 45 0 0 1

[[Image:spin.png|alt text]]
[[Image:spin2.png|alt text]]
=Shift=

Shifting means moving the object. It is used in same manner as old position-keyword. Without position-keyword, object is placed around 0 0 0. When shift moves it from origin, coordinates are just like with position. However, shift is repeatable, and sequential moves will use last point as origin.
[[Image:shift.png|alt text]]

=Shear=

Shearing is "a deformation of an object in which parallel planes remain parallel but are shifted in a direction parallel to themselves." If you don't understand, look at the image below. The three values after shear-keyword define a vector. Vectors lenght represents change per Z-axis unit. If you have 10 units high meshbox, and shear it by 1 0 0, top will move 10 * 1 away from the bottom in X-axis direction. In next example, we use shear to make an escalator with nice ends.

physics
name escalator
linear 15 0 15
end
meshbox
size 10 10 100
shear 2 0 0
phydrv escalator
end

meshbox
size 10 10 10
shear 1 0 0
end

[[Image:shear.png|alt text]]