Fix vector subscript out of range for models with partial textures

- Add bounds check in KDTreeSoup::weight() for invalid texture indices
- Add bounds checks in TexAtlas::width/height for invalid tex/level
- Add bounds checks in TexAtlas::read and TexPyramid::read
- Fix remap vector size in extractNodeTex (n_boxes instead of mesh.vert.size)
- Add defensive bounds checks throughout extractNodeTex

This fixes a crash when building Nexus files from models where not all
meshes have textures (e.g., SunglassesKhronos.glb with 5 meshes but
only 1 texture). The crash occurred on Windows Debug builds where
MSVC detects vector subscript out of range.

Author: HeDo88TH

src/nxsbuild/kdtree.cpp

@@ -365,6 +365,9 @@ void KDTreeSoup::pushTriangle(Triangle &t) {
 double KDTreeSoup::weight(Triangle &t) {
 	if(textures.size() == 0)
 		return 0;
+	// Skip weight calculation for triangles without valid texture
+	if(t.tex < 0 || t.tex >= (int)textures.size())
+		return 0;
 	Vertex &v0 = t.vertices[0];
 	Vertex &v1 = t.vertices[1];
 	Vertex &v2 = t.vertices[2];

src/nxsbuild/nexusbuilder.cpp

@@ -261,7 +261,7 @@ QImage NexusBuilder::extractNodeTex(TMesh &mesh, int level, float &error, float
 
 	//erase boxes assigned to no texture, and remap vertex_to_box
 	int count = 0;
-	std::vector<int> remap(mesh.vert.size(), -1);
+	std::vector<int> remap(n_boxes, -1);
 	for(int i = 0; i < n_boxes; i++) {
 		if(box_texture[i] == -1)
 			continue;
@@ -271,8 +271,12 @@ QImage NexusBuilder::extractNodeTex(TMesh &mesh, int level, float &error, float
 	}
 	boxes.resize(count);
 	box_texture.resize(count);
-	for(int &b: vertex_to_box)
-		b = remap[b];
+	for(int &b: vertex_to_box) {
+		if(b >= 0 && b < n_boxes)
+			b = remap[b];
+		else
+			b = -1;
+	}
 
 	std::vector<vcg::Point2i> sizes(boxes.size());
 	std::vector<vcg::Point2i> origins(boxes.size());
@@ -288,9 +292,11 @@ QImage NexusBuilder::extractNodeTex(TMesh &mesh, int level, float &error, float
 			}
 		}
 		int tex = box_texture[b];
+		if(tex < 0) continue;
 
 		float w = atlas.width(tex, level); //img->size().width();
 		float h = atlas.height(tex, level); //img->size().height();
+		if(w <= 0 || h <= 0) continue;
 		float px = 1/(float)w;
 		float py = 1/(float)h;
 		box.Offset(vcg::Point2f(px, py));
@@ -358,16 +364,24 @@ QImage NexusBuilder::extractNodeTex(TMesh &mesh, int level, float &error, float
 		auto &p = mesh.vert[i];
 		auto &uv = p.T().P();
 		int b = vertex_to_box[i];
-		if(b == -1) {
+		if(b == -1 || b >= (int)origins.size() || b >= (int)mapping.size() || b >= (int)box_texture.size()) {
 			uv = vcg::Point2f(0.0f, 0.0f);
 			continue;
 		}
 		vcg::Point2i &o = origins[b];
 		vcg::Point2i m = mapping[b];
 
 		int tex = box_texture[b];
+		if(tex < 0) {
+			uv = vcg::Point2f(0.0f, 0.0f);
+			continue;
+		}
 		float w = atlas.width(tex, level);
 		float h = atlas.height(tex, level);
+		if(w <= 0 || h <= 0) {
+			uv = vcg::Point2f(0.0f, 0.0f);
+			continue;
+		}
 		float px = 1/(float)w;
 		float py = 1/(float)h;
 
@@ -413,6 +427,7 @@ QImage NexusBuilder::extractNodeTex(TMesh &mesh, int level, float &error, float
 	for(int i = 0; i < mesh.face.size(); i++) {
 		auto &face = mesh.face[i];
 		int b = vertex_to_box[face.V(0) - &(mesh.vert[0])];
+		if(b < 0 || b >= (int)origins.size()) continue;
 		vcg::Point2i &o = origins[b];
 		vcg::Point2i m = mapping[b];
 		auto V0 = face.V(0)->T().P();
@@ -435,11 +450,13 @@ QImage NexusBuilder::extractNodeTex(TMesh &mesh, int level, float &error, float
 		color[0] = ((boxid % 16)*135)%127 + 127; */
 
 			int source = box_texture[i];
+			if(source < 0) continue;
 			vcg::Point2i &o = origins[i];
 			vcg::Point2i &s = sizes[i];
 
 			QImage rect = atlas.read(source, level, QRect(o[0], o[1], s[0], s[1]));
-			painter.drawImage(mapping[i][0], mapping[i][1], rect);
+			if(i < (int)mapping.size())
+				painter.drawImage(mapping[i][0], mapping[i][1], rect);
 
 			//		painter.fillRect(mapping[i][0], mapping[i][1], s[0], s[1], QColor(color[0], color[1], color[2]));
 			//		boxid++;
@@ -600,7 +617,6 @@ void NexusBuilder::processBlock(KDTreeSoup *input, StreamSoup *output, uint bloc
 		mesh_size = mesh1.serializedSize(header.signature);
 
 	} else {
-
 		input->lock(mesh, block);
 		//we need to replicate vertices where textured seams occours
 

src/nxsbuild/texpyramid.cpp

@@ -200,6 +200,7 @@ bool TexPyramid::init(int tex, TexAtlas *c, LoadTexture &file) {
 }
 
 QImage TexPyramid::read(int level, QRect region) {
+	if(level < 0 || level >= (int)levels.size()) return QImage();
 	return levels[level].read(region);
 }
 
@@ -237,6 +238,7 @@ bool TexAtlas::addTextures(std::vector<LoadTexture> &textures) {
 }
 
 QImage TexAtlas::read(int tex, int level, QRect region) {
+	if(tex < 0 || tex >= (int)pyramids.size()) return QImage();
 	return pyramids[tex].read(level, region);
 }
 

src/nxsbuild/texpyramid.h

@@ -90,8 +90,16 @@ class TexAtlas {
 	QImage read(int tex, int level, QRect region);
 	void buildLevel(int level);
 
-	int width(int tex, int level) { return pyramids[tex].levels[level].width; }
-	int height(int tex, int level) { return pyramids[tex].levels[level].height; }
+	int width(int tex, int level) { 
+		if(tex < 0 || tex >= (int)pyramids.size()) return 1;
+		if(level < 0 || level >= (int)pyramids[tex].levels.size()) return 1;
+		return pyramids[tex].levels[level].width; 
+	}
+	int height(int tex, int level) { 
+		if(tex < 0 || tex >= (int)pyramids.size()) return 1;
+		if(level < 0 || level >= (int)pyramids[tex].levels.size()) return 1;
+		return pyramids[tex].levels[level].height; 
+	}
 	void flush(int level);
 	void pruneCache();
 	void addImg(Index index, QImage img);