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feat(editor): add --gen-texture-flame fire pattern

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Vertical color gradient from dark (bottom) to hot (top), mixed
with multi-octave smooth noise so the flame boundary wavers
randomly rather than reading as a clean horizontal line.
Vertical position curve is squared so the dark stays dark
longer and the hot saturates faster — matches real-flame
appearance where most of the body is dark with a bright tip.

Useful for torches, braziers, magical effects, lava-zone set
dressing, fireplace texture details. Brings the procedural
texture pattern set to 32.
This commit is contained in:
Kelsi 2026-05-09 05:38:18 -07:00
parent c9831b38ff
commit e95dd7692b
3 changed files with 95 additions and 1 deletions
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92
tools/editor/cli_gen_texture.cpp
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@ -2700,6 +2700,95 @@ int handleCoral(int& i, int argc, char** argv) {
return 0;
}
int handleFlame(int& i, int argc, char** argv) {
// Flame: vertical color gradient from dark hex at the
// bottom to hot hex at the top, mixed with smooth noise
// flicker so the boundary between hot and dark wavers
// randomly. Reads as a flame seen from a distance.
std::string outPath = argv[++i];
std::string darkHex = argv[++i];
std::string hotHex = argv[++i];
uint32_t seed = 1;
int W = 256, H = 256;
if (i + 1 < argc && argv[i + 1][0] != '-') {
try { seed = static_cast<uint32_t>(std::stoul(argv[++i])); } catch (...) {}
}
if (i + 1 < argc && argv[i + 1][0] != '-') {
try { W = std::stoi(argv[++i]); } catch (...) {}
}
if (i + 1 < argc && argv[i + 1][0] != '-') {
try { H = std::stoi(argv[++i]); } catch (...) {}
}
if (W < 1 || H < 1 || W > 8192 || H > 8192) {
std::fprintf(stderr,
"gen-texture-flame: invalid dims (W/H 1..8192)\n");
return 1;
}
uint8_t dr, dg, db, hr, hg, hb;
if (!parseHex(darkHex, dr, dg, db)) {
std::fprintf(stderr,
"gen-texture-flame: '%s' is not a valid hex color\n",
darkHex.c_str());
return 1;
}
if (!parseHex(hotHex, hr, hg, hb)) {
std::fprintf(stderr,
"gen-texture-flame: '%s' is not a valid hex color\n",
hotHex.c_str());
return 1;
}
float seedF = static_cast<float>(seed);
auto noise = [&](float x, float y) -> float {
// Multi-octave smooth noise; lower freq dominates.
float n = 0.0f, total = 0.0f;
float freq = 0.04f, amp = 1.0f;
for (int o = 0; o < 3; ++o) {
n += amp * (0.5f + 0.5f *
std::sin(x * freq + seedF * (1.0f + o)) *
std::cos(y * freq + seedF * (0.5f + o)));
total += amp;
freq *= 2.0f;
amp *= 0.5f;
}
return n / total;
};
std::vector<uint8_t> pixels(static_cast<size_t>(W) * H * 3, 0);
for (int y = 0; y < H; ++y) {
// Vertical position: 0 at bottom (dark), 1 at top (hot).
float vy = static_cast<float>(H - 1 - y) / (H - 1);
for (int x = 0; x < W; ++x) {
// Add wavy flicker via noise so the gradient boundary
// isn't a clean horizontal line.
float n = noise(static_cast<float>(x), static_cast<float>(y));
float t = std::clamp(vy + (n - 0.5f) * 0.4f, 0.0f, 1.0f);
// Curve so the bottom stays dark longer and the top
// saturates faster (real flames are mostly dark with
// a bright core/tip).
t = t * t;
uint8_t r = static_cast<uint8_t>(dr * (1 - t) + hr * t);
uint8_t g = static_cast<uint8_t>(dg * (1 - t) + hg * t);
uint8_t b = static_cast<uint8_t>(db * (1 - t) + hb * t);
size_t i2 = (static_cast<size_t>(y) * W + x) * 3;
pixels[i2 + 0] = r;
pixels[i2 + 1] = g;
pixels[i2 + 2] = b;
}
}
if (!stbi_write_png(outPath.c_str(), W, H, 3,
pixels.data(), W * 3)) {
std::fprintf(stderr,
"gen-texture-flame: stbi_write_png failed for %s\n",
outPath.c_str());
return 1;
}
std::printf("Wrote %s\n", outPath.c_str());
std::printf(" size : %dx%d\n", W, H);
std::printf(" dark/hot : %s / %s\n",
darkHex.c_str(), hotHex.c_str());
std::printf(" seed : %u\n", seed);
return 0;
}
} // namespace
bool handleGenTexture(int& i, int argc, char** argv, int& outRc) {
@ -2789,6 +2878,9 @@ bool handleGenTexture(int& i, int argc, char** argv, int& outRc) {
if (std::strcmp(argv[i], "--gen-texture-coral") == 0 && i + 3 < argc) {
outRc = handleCoral(i, argc, argv); return true;
}
if (std::strcmp(argv[i], "--gen-texture-flame") == 0 && i + 3 < argc) {
outRc = handleFlame(i, argc, argv); return true;
}
return false;
}