On Thursday, 11 February 2016 at 13:05:41 UTC, Claude wrote:
Hello,

I come from the C world and try to do some procedural terrain generation, and I thought ndslice would help me to make things look clean, but I'm very new to those semantics and I need help.

Here's my problem: I have a C-style rough implementation of a function drawing a disk into a 2D buffer. Here it is:


import std.math;
import std.stdio;

void draw(ref float[16][16] buf, int x0, int y0, int x1, int y1)
{
    float xc = cast(float)(x0 + x1) / 2;
    float yc = cast(float)(y0 + y1) / 2;
    float xr = cast(float)(x1 - x0) / 2;
    float yr = cast(float)(y1 - y0) / 2;

    float disk(size_t x, size_t y)
    {
        float xx, yy;
        xx = (x - xc) / xr;
        yy = (y - yc) / yr;
        return 1.0 - sqrt(xx * xx + yy * yy);
    }

    for (int y = 0; y < 16; y++)
    {
        for (int x = 0; x < 16; x++)
        {
            buf[x][y] = disk(x, y);
            writef(" % 3.1f", buf[x][y]);
        }
        writeln("");
    }
}

void main()
{
    float[16][16] buf;

    draw(buf, 2, 2, 10, 10);
}


The final buffer contains values where positive floats are the inside of the disk, negative are outside, and 0's represents the perimeter of the disk.

I would like to simplify the code of draw() to make it look more something like:

Slice!(stuff) draw(int x0, int y0, int x1, int y1)
{
    float disk(size_t x, size_t y)
    {
        // ...same as above
    }

    return Slice!stuff.something!disk.somethingElseMaybe;
}

Is it possible?

Do I need to back-up the slice with an array, or could the slice be used lazily and modified as I want using some other drawing functions.

auto diskNoiseSlice = diskSlice.something!AddNoiseFunction;

... until I do a:

auto buf = mySlice.array;

... where the buffer would be allocated in memory and filled with the values according to all the drawing primitives I used on the slice.

I had a go at trying the sort of thing you are talking about: http://dpaste.dzfl.pl/8f9da4f4cc34

That won't work with std.experimental.ndslice in 2.070.0, so either use dmd git master or use the latest version of ndslice in mir (https://github.com/DlangScience/mir).

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