LIC

Line Integral Convolution Code based on the work of Cabral and Leedom: http://cs.brown.edu/courses/csci2370/2000/1999/cabral.pdf

Some old results: http://harperlangston.com/stokes/

DESCRIPTION:

There are two programs here: rand and main. By default, make makes main which runs the LIC. PLus, there's a script to convert to ppm for mpeg encoding. I'll describe the rand program first however (type make rand to create):

1. ./rand

   rand generates the n x m random noise image file, rand.pgm and the corresponding data file, rand.dat that can be taken as data for "main" (see below). rand.dat and rand .pgm by default is 100 x 100. To make them different sizes, use the options, -H Num1 and -W Num2. For example:

   ./rand -H 100 -W 400
   

   makes rand.dat and rand.pgm of height 100 and width 400. It's important that rand.dat is the same size as your input velocity field.

2. /.main

   (type make or make main to create)

   main takes a velocity field and input image and outputs a convoluted image according to LIC. The velocity file should be of the following format:

   ux_0 uy_0 uz_0 . . . ux_end uy_end uz_end

   I currently have the velocities at each point on different lines. That is:

   ux_0 uy_o uz_0 . . . ux_end uy_end uz_end

   but it shouldn't matter if you do it consecutively. Also, (ux_0, uy_0, uz_0) is the bottom left hand point's velocity and then the field is arranged to go to the right and then up to the next line such that (ux_end, uy_end, uz_end) is the top right point. If the data is different, you may have to flip the image accordingly either manually or in the code.

   The options for ./main are:

   -W Num : gives the width of the input velocity field and image -H Num : gives height (W and H default to 100 I believe) -in File : gives input image data of size H x W (defaults to rand.dat) make sure this is a pure .dat file, no pgm headers -out File : Name of the output pgm file. (defaults to either out.dat or out.pgm) -vel File : Name of input velocity field of size H x W ( x 3 for each of ux, uy and uz). Deafults to velocity.dat -L Num : Filterlength to be used. Defaults to 15. Play with this sum. Too short and nothing happens. Too long and output image looks horrible. 10 -20 seems pretty good.

   You can also play with the convolution coefficients in LIC which I'm going to allow to be changed from the command line since different coefficients seem to work for different velocity fields.

3. process_ppm file

   file is a pgm file which is turned into a ppm file using pgmtoppm and pnmdepth mostly, so make sure those scripts are on your machine. In the line: pgmtoppm rgbi: xx/xx/xx, each xx is an rgb value between 0 and 1 (float), so change that according to desired color. You can use mpeg2encode for movie making. See http://tns-www.lcs.mit.edu/manuals/mpeg2/ for information.