imagelib: load KTX2 cubemaps directly

engine/common/imagelib/img_ktx2.c

@@ -65,6 +65,22 @@ static void Image_KTX2Format( uint32_t ktx2_format )
 	}
 }
 
+static const int g_remap_cube_layer[6] = {
+/* Face order
+ 0   1   2   3   4   5  -- index
+ft, bk, up, dn, rt, lf  -- xash
++x, -x, +y, -y, +z, -z  -- KTX2
+rt, lf, bk, ft, up, dn  -- ref_vk
+
+texture[face] = ktx2[map[face]], e.g.:
+texture[rt] = ktx2[+z = 4]
+texture[lf] = ktx2[-z = 5]
+texture[bk] = ktx2[-x = 1]
+...
+*/
+	4, 5, 1, 0, 2, 3
+};
+
 static qboolean Image_KTX2Parse( const ktx2_header_t *header, const byte *buffer, fs_offset_t filesize )
 {
 	ktx2_index_t index;
@@ -93,7 +109,7 @@ static qboolean Image_KTX2Parse( const ktx2_header_t *header, const byte *buffer
 		return false;
 	}
 
-	if( header->faceCount > 1 )
+	if( header->faceCount != 1 && header->faceCount != 6 )
 	{
 		Con_DPrintf( S_ERROR "%s: unsupported KTX2 faceCount %d\n", __FUNCTION__, header->faceCount );
 		return false;
@@ -128,10 +144,10 @@ static qboolean Image_KTX2Parse( const ktx2_header_t *header, const byte *buffer
 		ktx2_level_t level;
 		memcpy( &level, levels_begin + mip * sizeof( level ), sizeof( level ));
 
-		if( mip_size != level.byteLength )
+		if( mip_size * header->faceCount != level.byteLength )
 		{
-			Con_DPrintf( S_ERROR "%s: mip=%d size mismatch read=%d, but computed=%d\n",
-				__FUNCTION__, mip, (int)level.byteLength, mip_size );
+			Con_DPrintf( S_ERROR "%s: mip=%d size mismatch read=%d, but computed=%d(mip=%d * faces=%d)\n",
+				__FUNCTION__, mip, (int)level.byteLength, mip_size * header->faceCount, mip_size, header->faceCount );
 			return false;
 		}
 
@@ -139,8 +155,11 @@ static qboolean Image_KTX2Parse( const ktx2_header_t *header, const byte *buffer
 		max_offset = Q_max( max_offset, level.byteLength + level.byteOffset );
 	}
 
-	if( max_offset > filesize )
+	if( max_offset > filesize ) {
+		Con_DPrintf( S_ERROR "%s: size to read %d exceeds file size %d\n",
+			__FUNCTION__, (int)max_offset, (int)filesize );
 		return false;
+	}
 
 	image.size = total_size;
 	image.num_mips = header->levelCount;
@@ -148,12 +167,25 @@ static qboolean Image_KTX2Parse( const ktx2_header_t *header, const byte *buffer
 	image.rgba = Mem_Malloc( host.imagepool, image.size );
 	memcpy( image.rgba, buffer, image.size );
 
-	for( int mip = 0, cursor = 0; mip < header->levelCount; ++mip )
+	int cursors[6] = {0};
+	if ( header->faceCount == 6 ) {
+		image.flags |= IMAGE_CUBEMAP;
+
+		for ( int face = 0; face < header->faceCount; ++face )
+			cursors[face] = g_remap_cube_layer[face] * total_size / header->faceCount;
+	}
+
+	for( int mip = 0; mip < header->levelCount; ++mip )
 	{
 		ktx2_level_t level;
 		memcpy( &level, levels_begin + mip * sizeof( level ), sizeof( level ));
-		memcpy( image.rgba + cursor, buffer + level.byteOffset, level.byteLength );
-		cursor += level.byteLength;
+
+		const int face_size = level.byteLength / header->faceCount;
+		for ( int face = 0; face < header->faceCount; ++face )
+		{
+			memcpy( image.rgba + cursors[face], buffer + level.byteOffset + face * face_size, face_size );
+			cursors[face] += face_size;
+		}
 	}
 
 	return true;
@@ -179,7 +211,7 @@ qboolean Image_LoadKTX2( const char *name, const byte *buffer, fs_offset_t files
 	image.depth = Q_max( 1, header.pixelDepth );
 	image.num_mips = 1;
 
-	ClearBits( image.flags, IMAGE_HAS_COLOR | IMAGE_HAS_ALPHA | IMAGE_HAS_LUMA );
+	ClearBits( image.flags, IMAGE_HAS_COLOR | IMAGE_HAS_ALPHA | IMAGE_HAS_LUMA | IMAGE_CUBEMAP );
 
 	if( !Image_KTX2Parse( &header, buffer, filesize ))
 	{

ref/vk/NOTES.md

@@ -1032,7 +1032,7 @@ This would also allow passing arbitrary per-pixel data from shaders, which would
             - `R_VkTextureSkyboxUpload(sides)`
     - if failed and not default already: `R_TextureSetupSky(default)` (recurse)
 
-# 2023-12-14 E34a
+# 2023-12-14 E347
 ## TIL engine imagelib `FS_LoadImage()`:
 1. Pick format based on extension
 2. If no extension is specified, try all supported extensions in sequence.
@@ -1044,3 +1044,38 @@ This would also allow passing arbitrary per-pixel data from shaders, which would
   rotate some compressed format, which will amount to just reordering blocks, and then reordering block
   contents. Mendokusai). Therefore, we can't just replace png sides with compressed ktx2 sides directly.
   KTX2 sides should be pre-rotated.
+
+# 2023-12-15 E348
+## Textures layout
+imagelib image buffer layout:
+	- sides[1|6]
+		- mips[biggest -> smallest]
+			- (pixel data)
+
+KTX2 file layout:
+- mips[smallest -> biggest]
+	- sides[1|6]
+		- (pixel data)
+
+# 2023-12-18 E349
+## Xash vs KTX2/vk cubemap face order
+Vulkan order:
++X, -X, +Y, -Y, +Z, -Z
+rt, lf, bk, ft, up, dn
+ 0,  1,  2,  3,  4,  5
+
+Xash order:
+ft, bk, up, dn, rt, lf
+
+Remap (KTX2 -> xash || xash[face] = KTX2[map[face]]):
+ 3,  2,  4,  5,  0,  1
+
+Remap (xash -> vk, vk[map[face]] = xash[face]):
+ 4,  5,  1,  0,  2,  3
+??? this shoudln't work
+
+default cubemap order:
+xash   vk (remapped)
++Y = -X
++X = +Z
++Z = +Y

ref/vk/TODO.md

@@ -1,7 +1,11 @@
+# 2023-12-18 E349
+- [x] KTX2 cubemaps
+- [ ] improve logs "vk/tex: Loaded skybox pbr/env/%.*s"
+- [ ] variable cubemap exposure
+- [ ] add skybox test
+
 # 2023-12-15 E348
 - [x] fix ktx2 sides corruption
-- [ ] KTX2 cubemaps
-- [ ] add skybox test
 
 # 2023-12-14 E346-E347
 - [x] Optimize skybox loading, #706