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direction_filter(display) Display direction_filter(display)

NAME

direction_filter - generate scalar values based on projection of vector values onto specified direction.

DESCRIPTION

The direction_filter object takes as input a display_data object and generates on output scalar data based on the projection of the velocity vector onto a specified direction. The original geometry and other information is passed through the filter, only the scalar data is modified.

A common use of the direction_filter is to color objects based on the direction they are moving. For example, given a group of spheres moving in various direction, they can be colored based on whether the spheres are moving "up" or "down". Of course the definition of up or down is provided by the direction instance variable.

SUPERCLASS

display_filter

INSTANCE VARIABLES

direction the vector used to project the point velocity against to generate scalar data. Points moving with the highest velocity along the direction vector will have the highest scalar values. By default direction=(0,0,1).

range specifies the (min,max) range that scalar values are mapped into. By default range=(0,1).

MESSAGES

direction= (x,y,z) set the value of the direction (i.e., projection vector)

direction? get the value of direction

range? get the current range.

range= (min,max) set the current range.

EXAMPLE

In this example a display data is created consisting of points and vector values. An direction_filter is used to assign scalar values to the points. Then using the data primitive, spheres are placed at each point and colored appropriately.

* Script to test direction filter */ display_data new: dd points=( .1,.1,-1, 0,0,0, 0,.1,2, .1,0,5 ) vectors=( 0,0,1, .1,.5,.8, .4,0,-.7, 0,0,-2 ) ; direction_filter new: df data_in= dd direction=(0,0,1) range=(10,99) ; sphere_modeller new: sm debugon! resolution=2 radius =0.10 ; data_primitive new: dp debugon! data_in= df source= sm scaling_off! ; display_all new: da data_in= dp range=[df range?] ; actor new: a modeller=da ;

camera new: acamera on! position=(1,0,0) x_range=(-5,5) y_range=(-5,5) z_range=(-5,5) default! ; renderer new: aren actors=[actor instances?] cameras=acamera render! ;