軌跡 - Siv3D/Reference-JP GitHub Wiki

# include <Siv3D.hpp>

const Image CreateGradation()
{
    Image image(1, 512);

    for (int32 y = 0; y <= 255; ++y)
    {
        image[y][0] = ColorF(Smoothstep(0, 1, y / 255.0));
    }

    for (int32 y = 256; y < 512; ++y)
    {
        image[y][0] = ColorF(Smoothstep(0, 1, (511 - y) / 255.0));
    }

    return image;
}

void Main()
{
    const Texture texture(CreateGradation(), TextureDesc::Mipped);

    const int size = 640;
    const int vSize = size * 2;
    const int iSize = (size - 1) * 6;

    Sprite sprite(vSize, iSize);

    for (auto i : step(size))
    {
        sprite.vertices[i * 2 + 0].pos = Float2(i, 10);
        sprite.vertices[i * 2 + 0].color.set(255, 120, 255);
        sprite.vertices[i * 2 + 0].tex.set(0.0, 0.0);

        sprite.vertices[i * 2 + 1].pos = Float2(i, 50);
        sprite.vertices[i * 2 + 1].color.set(255, 90, 255);
        sprite.vertices[i * 2 + 1].tex.set(0.0, 1.0);
    }

    for (uint16 i = 0; i < size - 1; ++i)
    {
        sprite.indices[i * 6 + 0] = i * 2 + 0;
        sprite.indices[i * 6 + 1] = i * 2 + 2;
        sprite.indices[i * 6 + 2] = i * 2 + 1;

        sprite.indices[i * 6 + 3] = i * 2 + 3;
        sprite.indices[i * 6 + 4] = i * 2 + 1;
        sprite.indices[i * 6 + 5] = i * 2 + 2;
    }

    Graphics2D::SetBlendState(BlendState::Additive);

    PerlinNoise noise;

    while (System::Update())
    {
        const int32 count = System::FrameCount();

        for (auto n : step(6))
        {
            const Color color = HSV(n * 20 + count % 360).toColor(96);

            for (auto i : step(size))
            {
                const double t = count *0.4f + i *0.05f + n * 2.0f;
                const double a = 200 + noise.noise(t*0.015) * 300;
                const double b = a + 40 + noise.noise(t*0.05) * 40;

                sprite.vertices[i * 2 + 0].pos = Float2(i, a);
                sprite.vertices[i * 2 + 0].color = color;

                sprite.vertices[i * 2 + 1].pos = Float2(i, b);
                sprite.vertices[i * 2 + 1].color = color;
            }

            sprite.draw(texture);
        }
    }
}