f8103c4 · dc-terrain · pear-git-v3

dc-terrain commits / f8103c4

atlas: emit HBLK_ATLAS_W + HBLK_USE_ATLAS so binding 14 can actually be read

Binding 14 has been allocated, uploaded and bound since it was added, and never
READ — HBLK_USE_ATLAS appeared in two comments and was defined nowhere. Worse,
dc_shader_source.h:200 claims "the generator emits HBLK_ATLAS_W beside the block
constants" and it did not: that identifier existed only inside that sentence.

  - dc_compute.h gains `static constexpr int ATLAS_W = 4096` as the ONE
    definition. _upload_atlas lays the texture out with it and the generator
    emits it into the shader. Two copies of this number that disagree would be a
    SHEAR, not a crash — every sample lands on the wrong row and the terrain is
    silently wrong.
  - the generator emits HBLK_ATLAS_W and HBLK_USE_ATLAS beside HBLK_N, at BOTH
    emit sites (the heightfield_only path and the live node path).
  - the switch is an ENV VAR, not a property, deliberately: the point is to run
    the same unchanged scene BOTH ways, and a property would have to be authored
    into the map to be flipped.

Built debug AND release for dc-terrain and proc-nodes — the .so files are
symlinks into each repo's bin/ and are not built by CI, so a half-built pair is
how a stale extension segfaults.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

f8103c41b768f4edf297a7523472b5deeea3b441

by plankatron <fleeky@gmail.com> · 2026-09-03T16:40:41.000Z

Changed files (3) +29 -1

src/dc_compute.cpp +1 -1

…	…	@@ -397,7 +397,7 @@ void DCCompute::_upload_atlas(const float* data, int n) {
397	397	if (atlas_tex_.is_valid()) { rd_->free_rid(atlas_tex_); atlas_tex_ = RID(); }
398	398	if (atlas_staging_.is_valid()) { rd_->free_rid(atlas_staging_); atlas_staging_ = RID(); }
399	399
400		const int W = 4096;
	400	const int W = ATLAS_W; // see dc_compute.h — the generator emits this same number
401	401	int count = (data == nullptr \|\| n <= 0) ? 1 : n;
402	402	int H = (count + W - 1) / W;
403	403	atlas_w_ = W; atlas_h_ = H;

src/dc_compute.h +7 -0

…	…	@@ -138,6 +138,13 @@ private:
138	138	// shader chooses with HBLK_USE_ATLAS, so the two can be compared against
139	139	// each other rather than the swap being taken on faith. A half-migration
140	140	// here is exactly what shipped #55's count/size SIGSEGV.
	141	// THE atlas width. ONE definition: _upload_atlas lays the texture out with
	142	// it and the generator emits it into the shader as HBLK_ATLAS_W. Two copies
	143	// of this number that disagree is a shear, not a crash — every sample lands
	144	// on the wrong row and the terrain is silently wrong.
	145	public:
	146	static constexpr int ATLAS_W = 4096;
	147	private:
141	148	RID atlas_tex_; // R32F, linear index -> (x, y); binding 14
142	149	RID atlas_staging_; // one row-block, for texture_update + copy
143	150	int atlas_w_ = 0;

src/dc_terrain_generator_procnodes.cpp +21 -0

…	…	@@ -16,7 +16,9 @@
16	16	// comment still stands. It is a shared math header and nothing more.
17	17	#include "erosion_cpp_shim.h"
18	18	#include "erosion_wrapper_glsl.h"
	19	#include "dc_compute.h"
19	20	#include <godot_cpp/classes/file_access.hpp>
	21	#include <godot_cpp/classes/os.hpp>
20	22
21	23	namespace godot {
22	24
…	…	@@ -526,6 +528,21 @@ void DCTerrainGeneratorProcNodes::set_graph(const Ref<Resource> &p_graph) {
526	528	//
527	529	// One producer for now, which matches one bound buffer. More than one wants an
528	530	// offset table emitted alongside, which is the same change a grid of tiles needs.
	531	// Read the SAME floats through binding 14 (the atlas image) instead of binding
	532	// 13 (the SSBO). Both hold identical values at identical indices, so this is a
	533	// pure TRANSPORT swap and gate_dc_vs_lookdev must agree to 0.001 m either way.
	534	//
	535	// An ENV VAR rather than a property, deliberately: the point is to run the gate
	536	// BOTH ways over one unchanged scene, and a property would have to be authored
	537	// into the map to be flipped.
	538	//
	539	// HBLK_USE_ATLAS=1 godot4 --path . --script res://scenes/test/...
	540	static bool _use_atlas() {
	541	String v = OS::get_singleton()->get_environment("HBLK_USE_ATLAS");
	542	return v == "1" \|\| v.to_lower() == "true";
	543	}
	544
	545
529	546	void DCTerrainGeneratorProcNodes::_collect_node_data() {
530	547	if (graph_.is_null()) return;
531	548	Variant nc_var = graph_->call("get_node_count");
…	…	@@ -733,6 +750,8 @@ void DCTerrainGeneratorProcNodes::_recompile_glsl() {
733	750	if (heightfield_only_ && hblk_n_ > 0) {
734	751	String hb =
735	752	String("const int HBLK_N = ") + itos(hblk_n_) + ";\n"
	753	"const int HBLK_ATLAS_W = " + itos(DCCompute::ATLAS_W) + ";\n"
	754	"const bool HBLK_USE_ATLAS = " + String(_use_atlas() ? "true" : "false") + ";\n"
736	755	"const float HBLK_OX = " + String::num(hblk_ox_, 4) + ";\n"
737	756	"const float HBLK_OZ = " + String::num(hblk_oz_, 4) + ";\n"
738	757	"const float HBLK_MPP = " + String::num(hblk_mpp_, 6) + ";\n"
…	…	@@ -861,6 +880,8 @@ void DCTerrainGeneratorProcNodes::_recompile_glsl() {
861	880	// that never compiled and a world with no terrain.
862	881	hblk_glsl_sampler =
863	882	String("const int HBLK_N = ") + itos(hblk_n_) + ";\n"
	883	"const int HBLK_ATLAS_W = " + itos(DCCompute::ATLAS_W) + ";\n"
	884	"const bool HBLK_USE_ATLAS = " + String(_use_atlas() ? "true" : "false") + ";\n"
864	885	"const float HBLK_OX = " + String::num(hblk_ox_, 4) + ";\n"
865	886	"const float HBLK_OZ = " + String::num(hblk_oz_, 4) + ";\n"
866	887	"const float HBLK_MPP = " + String::num(hblk_mpp_, 6) + ";\n"