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#include <stdio.h>
#define P(A) fprintf(stderr,"%s\n",A)
void print_algorithm()
{
P("This program uses a modified form the mid-point displacement algorithm");
P("");
P("The mid-point displacement algorithm is a recursive algorithm, each iteration");
P("doubles the resolution of the grid. This is done in 2 stages.");
P("");
P("A B A B A F B");
P(" stage1 stage2");
P(" ---------> E --------> G E H");
P("");
P("C D C D C I D");
P("");
P("The new points are generated by taking an average of the surrounding points");
P("and adding a random offset.");
P("The modifications to the standard algorith are as follows:");
P("There are three optional regeneration steps to reduce \"creasing\". A");
P("regeneration step recalculates the height of existing points using an");
P("average and offset from a newer generation of points. The three");
P("regeneration steps are:");
P(" rg1: recalculate corner points (A,B,C,D) from the midpoints (E)");
P(" after the stage1 update.");
P(" rg2: recalculate midpoints (E) from the edge points (F,G,H,I)");
P(" after the stage2 update");
P(" rg3: recalculate corner points (A,B,C,D) from the edge points (F,G,H,I)");
P(" after the stage2 update");
P("The regeneration stages are turned on by the smoothing parameter (-s flag)");
P("");
P(" flag rg3 rg2 rg1");
P(" 0 off off off");
P(" 1 on off off");
P(" 2 off on off");
P(" 3 on on off");
P(" 4 off off on");
P(" 5 on off on");
P(" 6 off on on");
P(" 7 on on on");
P("");
P("When performing the regeneration steps the random offset is added to a");
P("weighted average of the previous value of the point and a the average of");
P("the new points. The weighting factors are controlled by the -X and -Y flags.");
P("");
P("The -x flag (cross update) controls whether the midpoints (E) are included");
P("in the average when performing the stage2 update or if only the corner");
P("points are used.");
P("");
}
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