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Issue #3: wreck scorch quad ramp + RGBA4444 alpha cutout (the 'dark square')

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MECHMD's scorch base (basev:bvx9_mtl, bexp9_tex = BEXP.BSL RGBA4444
slice 8, ramp cdusty) drew as a hard-edged dark square for two stacked
reasons:

1. The blanket 'truecolor BSL slice (channel >= 6) never ramps' gate
   blocked its cdusty ramp.  Corpus scan: only 4 shipped textures use
   truecolor slices; bexp9/bdet9 are grayscale in RGB (100% / 98.8%
   r==g==b) and their materials author ramps -- only bdam8 (damage
   sheet) is truly coloured.  bgfload rampableSlice() now probes the
   decoded slice: a truecolor slice ramps iff effectively gray (>=95%),
   keeping bdam8's colour protected.

2. The RGBA4444 authored alpha channel -- a binary 0/240 cutout mask
   (the splat silhouette, 78.5% transparent) -- was never alpha-tested,
   so the quad's transparent surround rendered as an opaque rectangle.
   New BgfDrawBatch.texAlpha (channel >= 8) routes these batches
   through the PUNCH alpha-test draw states, WITHOUT the black-texel
   keying (which would hole the near-black charred centre).  Side
   benefit: tree9 (tree/leaf cards) + bdet9 (trans-rail lattice) get
   their authored cutouts too.

Pixel-verified (ram-kill run, BT_SHOT): irregular char splat, dark
brown (71,44,34) lifting to near-terrain tan (115,100,91 vs terrain
131,119,108), no rectangle; pre-death frames unregressed (vehicles
stay lit/diffuse -- hasNormals gate untouched).  Awaiting human
verification.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
arcattack
2026-07-19 10:39:43 -05:00
co-authored by Claude Fable 5
parent 557e9fd243
commit 9fff079df4
4 changed files with 83 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
engine/MUNGA_L4/bgfload.cpp
+46 -4
View File
@@ -1,6 +1,7 @@
// bgfload.cpp - see bgfload.h. Parse logic ported from port/src/bgf.cpp; directory
// scanning reimplemented on Win32 (FindFirstFile) so it builds under C++14.
#include "bgfload.h"
#include "image.h" // truecolor-slice grayscale probe (rampableSlice, issue #3)
#include <windows.h>
#include <cstdio>
@@ -247,6 +248,40 @@ bool hasNormals(uint16_t id) {
return id == TAG_VERTEX_XYZ_N || id == TAG_VERTEX_XYZ_N_UV;
}
// TRUECOLOR-slice ramp eligibility (issue #3, the wreck scorch quad). Only 4
// shipped textures use a truecolor BSL slice (bdam8=RGB444; bdet9/bexp9/tree9=
// RGBA4444). bexp9 (MECHMD's scorch splat, material basev:bvx9_mtl ramp
// 'cdusty') and bdet9 (the trans-rail lattice, ramps 'softer'/'cdusty') are
// GRAYSCALE in their RGB (100% / 98.8% r==g==b texels, corpus-measured) -- they
// author the same luminance->ramp colouring as every mono slice, and the old
// blanket "channel < 6" gate left the scorch a raw dark quad instead of the
// cdusty dark-brown->dusty-tan gradient. bdam8 (the damage sheet) is genuinely
// COLOURED (33% non-gray texels) -- luminance-ramping it would destroy its
// colour, which is what the blanket gate was protecting. Gate on the actual
// slice content: a truecolor slice ramps only when its RGB is effectively
// grayscale. Cached per path#channel (decode runs once per texture).
bool rampableSlice(const std::string& texPath, int channel) {
if (channel < 6 || texPath.empty()) return true; // mono slices always ramp-eligible
static std::map<std::string, bool> cache;
std::string key = texPath;
key += '#';
key += (char)('0' + (channel % 10));
auto it = cache.find(key);
if (it != cache.end()) return it->second;
bool gray = false;
Image img = decodeImage(texPath, channel);
if (img.ok && !img.argb.empty()) {
size_t same = 0;
for (uint32_t p : img.argb) {
const uint8_t r = (uint8_t)(p >> 16), g = (uint8_t)(p >> 8), b = (uint8_t)p;
if (r == g && g == b) ++same;
}
gray = ((float)same / (float)img.argb.size()) >= 0.95f;
}
cache[key] = gray;
return gray;
}
struct Chunk {
uint16_t id = 0;
const uint8_t* data = nullptr;
@@ -689,10 +724,13 @@ struct Builder {
// RAMP applies ONLY to no-normal geometry (see hasNormals()): normal-bearing
// vehicle/missile batches keep their material diffuse colour + texture (lit path),
// so they must NOT be ramped even when the material carries a ramp ref (cdusty).
// TRUECOLOR BSL slices (channel >= 6: RGB444/RGBA4444, e.g. damcolor's bdam8
// damage sheet) are real colour images -- luminance-ramping them would
// destroy their colour, so they take the plain textured path.
const bool useRamp = currentHasRamp && (!hasNormals(vtag) || currentTSphere) && currentTexChannel < 6;
// TRUECOLOR BSL slices (channel >= 6: RGB444/RGBA4444) ramp only when their RGB
// is effectively GRAYSCALE (rampableSlice): bexp9/bdet9 are authored gray + ramp
// (the wreck scorch splat's cdusty gradient, issue #3); damcolor's bdam8 damage
// sheet is a real colour image -- luminance-ramping it would destroy its colour,
// so it takes the plain textured path.
const bool useRamp = currentHasRamp && (!hasNormals(vtag) || currentTSphere)
&& rampableSlice(currentTex, currentTexChannel);
const uint32_t base = (uint32_t)px.size();
const uint32_t localCount = (uint32_t)lx.size();
@@ -839,6 +877,10 @@ struct Builder {
batch.texScrollU = currentTexScrollU;
batch.texScrollV = currentTexScrollV;
batch.vertexAlpha = vertexAlpha;
// RGBA4444 slice (channel >= 8): the texture's AUTHORED alpha channel is
// a cutout mask (bexp9 scorch splat / bdet9 rail lattice / tree9 cards)
// -- the renderer alpha-tests it in the opaque pass (see bgfload.h).
batch.texAlpha = (currentTexChannel >= 8) && !currentTex.empty();
batch.hasRamp = useRamp;
// tsphere warp flag: warpBands>0 signals L4D3D's ramp bake to CONTRAST-
// COMPRESS the bintA cloud toward mid-grey (BT_WARP_CONTRAST) before applying