effector/src/effects/datamosh.cpp

#include "effects/datamosh.hpp"

#include <algorithm>
#include <cmath>
#include <string>
#include <vector>

#include "effects/corrupt_blocks.hpp"
#include "effects/sampling.hpp"

namespace effector {

const std::vector<ParamSpec>& DatamoshEffect::params() const {
    static const std::vector<ParamSpec> specs = {
        ParamSpec::makeInt("mosh_block", "Block size", 16, 2, 256,
                           "Width and height in pixels of one block, as a codec would cut them."),
        ParamSpec::makeDouble("mosh_rate", "Rate", 0.1, 0.0, 1.0,
                              "Chance of each block breaking at some moment of the cycle."),
        ParamSpec::makeChoice("mosh_kinds", "Damage", "mixed",
                              {"mixed", "repeat", "displace", "colour"},
                              "repeat freezes a block into a copy of the one to its left, "
                              "displace pulls one in from elsewhere in the image, colour knocks "
                              "it off colour; mixed picks one of them for every block."),
        ParamSpec::makeDouble("mosh_hold", "Hold", 0.3, 0.01, 1.0,
                              "How much of each cycle a broken block stays broken, give or take "
                              "half; 1 keeps it broken throughout."),
        ParamSpec::makeInt("mosh_drift", "Drift", 24, 0, 4096,
                           "How far in pixels a displaced block's picture slides while it "
                           "shows."),
        ParamSpec::makeDouble("mosh_speed", "Speed", 0.5, 0.0, 10.0,
                              "Cycles per second, rounded so that the clip loops without a jump; "
                              "0 holds still.",
                              0.05, 2),
        ParamSpec::makeBool("mosh_bleed", "Bleed", false,
                            "Carry each broken block's fault on to the end of its row, the way "
                            "one broken bit spoils the rest of a stream."),
    };
    return specs;
}

namespace {

struct Settings {
    int size;
    double rate;
    std::string kinds;
    double hold;
    int drift;
    double speed;
    bool bleed;

    explicit Settings(const ParamValues& values)
        : size(static_cast<int>(std::max(2L, paramInt(values, "mosh_block", 16)))),
          rate(std::clamp(paramDouble(values, "mosh_rate", 0.1), 0.0, 1.0)),
          kinds(paramChoice(values, "mosh_kinds", "mixed")),
          hold(std::clamp(paramDouble(values, "mosh_hold", 0.3), 0.01, 1.0)),
          drift(static_cast<int>(std::max(0L, paramInt(values, "mosh_drift", 24)))),
          speed(std::max(0.0, paramDouble(values, "mosh_speed", 0.5))),
          bleed(paramBool(values, "mosh_bleed", false)) {}
};

// A block that breaks at some moment of the cycle: how, from when, for how
// long (both as parts of a cycle), and which way a displaced one smears.
struct Break {
    Block block;
    double start = 0.0;
    double length = 0.0;
    double driftX = 0.0;
    double driftY = 0.0;
};

}  // namespace

Image DatamoshEffect::animate(Image input, const ParamValues& values, const Moment& at) const {
    const Settings settings(values);
    const int width = input.width();
    const int height = input.height();
    const int size = settings.size;
    const int cols = (width + size - 1) / size;
    const int rows = (height + size - 1) / size;

    // What stays put for the whole clip: the whole map of breaks, block by
    // block in reading order, as Corrupt draws its damage.
    Rng steady = at.steady();
    std::vector<Break> breaks(static_cast<std::size_t>(cols) * rows);
    bool any = false;
    for (int by = 0; by < rows; ++by) {
        const Break* carried = nullptr;
        for (int bx = 0; bx < cols; ++bx) {
            Break& piece = breaks[static_cast<std::size_t>(by) * cols + bx];
            if (carried != nullptr) {
                piece = *carried;
                // A displaced run keeps moving along with the row, so the
                // stretch reads as one shifted strip.
                if (piece.block.damage == Damage::Displace) piece.block.sx += size;
                carried = &piece;
                continue;
            }
            if (!chance(steady.next(), settings.rate)) continue;
            piece.block = drawDamage(steady, settings.kinds, bx, width, height, size);
            piece.start = unitDouble(steady.next());
            piece.length = std::min(1.0, settings.hold * (0.5 + unitDouble(steady.next())));
            sinCosDegrees(unitDouble(steady.next()) * 360.0, piece.driftY, piece.driftX);
            if (settings.bleed) carried = &piece;
            any = true;
        }
    }
    if (!any) return input;

    // Where this frame is in time: which blocks are broken, and how far
    // through its stretch each displaced one is.
    const double t = settings.speed > 0.0 ? at.cycle(settings.speed) : 0.0;
    std::vector<Block> plan(breaks.size());
    for (std::size_t i = 0; i < breaks.size(); ++i) {
        const Break& piece = breaks[i];
        if (piece.block.damage == Damage::None) continue;
        const double into = t - piece.start - std::floor(t - piece.start);
        if (piece.length < 1.0 && into >= piece.length) continue;
        Block& block = plan[i];
        block = piece.block;
        if (block.damage == Damage::Displace && settings.drift > 0) {
            const double slide = settings.drift * into / piece.length;
            const int sx = block.sx + static_cast<int>(std::lround(slide * piece.driftX));
            block.sx = (sx % width + width) % width;
            block.sy = std::clamp(block.sy + static_cast<int>(std::lround(slide * piece.driftY)), 0,
                                  height - 1);
        }
    }

    Image canvas = input;
    paintBlocks(canvas, input, plan, cols, rows, size);
    return canvas;
}

}  // namespace effector