flutter3d_shaders 0.6.0

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• Six samples taken under a branch ask for a mip level by name. texture derives its level from the difference between neighbouring invocations, and that difference is only defined where all four invocations of a quad arrive together. Five files were taking a sample where they do not: the cascade search returns early, the light loop skips a light facing away, the reflection march breaks when a ray leaves the frame, the ambient-occlusion loop continues past a sample outside it. A WGSL backend refuses exactly that, which is how they were found. Four of the five — shadow.glsl, surface.glsl, reflections.frag, ssao.frag — now call textureLod(..., 0.0) at six call sites.
• Not a picture change on any backend, and that is the point. Every texture involved is a render target with a single level — the cascade atlas, the two point-shadow atlases, the surface buffer, the scene colour — so level zero is the level the derivative was selecting anyway. Naming it costs nothing and removes the undefined behaviour rather than papering over it.
• The normal map is the one that could not be pinned, so it was hoisted instead. ApplyNormalMap samples before the degenerate-tangent test rather than under it. That map really is mipped — read at full resolution on a surface turned away from the camera it is the widest disagreement there has ever been between backends — so forcing level zero would have changed the picture. The sample now happens above the branch, reads the same texel the branch would have read, and pays for one unused fetch in the rare case.
• Nothing was added to or removed from the header set, and no entry point changed name, so a bundle built against 0.5.2 answers to the same list.

• Every texture read under a branch names its level or moves above the branch. WGSL will only derive a mip level where all four invocations of a quad agree to be, and six lit and screen-space stages sampled under a condition that does not promise it — a light the surface faces away from, a cascade that misses the fragment, a ray already off the frame, a tangent too degenerate to build a frame from. The cascade atlas, both point-shadow atlases, the surface buffer and the scene colour are single-level render targets, so lib/shadow.glsl, lib/surface.glsl, post/reflections.frag and post/ssao.frag read them with textureLod at level zero — the level the derivative was choosing anyway. lib/material_maps.glsl does the opposite, because a normal map's mip chain is real and pinning it would blur or sharpen the picture: the sample moves above the degenerate-tangent test instead. Nothing any backend draws changes.
• lib/morph.glsl: a vertex moved towards the shapes its mesh carries. Deltas in an r32g32b32a32Float texture — one column a vertex, three rows a target — read by gl_VertexIndex and blended by up to eight weights. A texture rather than vertex attributes because the layout here is structural: the in declarations of mesh.vert are the layout, and deltas as attributes would mean a second vertex shader for each lighting model.
• lib/morph_instanced.glsl, included by mesh_instanced.vert alone: the same blend with each instance's weights, read by gl_InstanceIndex from a texture of one row a slot. A file of its own because a sampler declared in lib/morph.glsl would be declared on all four mesh vertex stages and bound by every draw for ever; the deltas are worth that and a second sampler three stages can never use is not. ApplyMorph's delta read is split out as AddMorphTarget so both paths reach a texel through the same three lines.
• Read with texture() at texel centres rather than texelFetch, and handed the texel size in the uniform rather than asking textureSize: impellerc aborts on texelFetch in a vertex stage.
• mesh.vert, mesh_skinned.vert, mesh_instanced.vert and mesh_lightmapped.vert all morph before their transform — the skinned one in the rest pose first, the instanced one before the instance matrix, since the deltas are in the mesh's own space and a batch shares its mesh.
• A probe pair, probe/vertex_texture.vert and .frag, which passes what the vertex stage sampled through to the fragment stage. It is how the conformance suite asks whether a backend can do this at all.

The surface buffer's alpha changes meaning, and FogInfo gains a member. Breaking for anything that declares that block or reads that channel. It goes out as a patch because nothing outside this repository has taken a dependency on 0.5.0 yet; the entry says what it is rather than what the number implies.

• frag_surface.a holds the depth along the view axis in world metres, where it held gl_FragCoord.z. The attachment is r16g16b16a16Float on every backend, and a window depth spends nearly the whole of [0, 1] on the first few metres — past twenty, one half-float step is wider than half a metre, so a wall at twenty and one at twenty and a half stored the same number. Both passes that read this buffer decide occlusion by subtracting two of them, and the rounding decided whole bands of the frame: vertical stripes along the lines of equal depth, on both GPU backends, in every scene with a wall in it. WriteSurfaceGeometry and the new ViewDepth beside EyeDistance carry the reasoning.
• FogInfo gains vec4 forward, the camera's world-space direction, which is what a fragment needs to compute that depth. A custom lit shader that declares this block must declare the member: the engine binds it, and a backend that checks its bindings refuses one the shader does not have. The three particle stages declare the block without it on purpose — a particle writes no surface buffer — and are bound without it.
• SsaoInfo and ReflectionInfo gain vec4 forward beside camera. Reconstructing a point from the stored depth is now a ray crossed with a plane, and both ends of the pixel's ray are unprojected rather than one end and the camera position: an orthographic camera's rays are parallel and meet nowhere, so the cheaper version is right on a perspective camera and wrong on every isometric scene. reflections.frag takes its view vector from that ray as well.

• No API change. Released with the set.

• Luminance: the lit scene's log luminance at low resolution, sixteen taps per texel, encoded in eight bits over sixteen stops from minus ten — what an exposure meter reads back. LuminanceInfo.params carries the footprint and the two ends of the encoding.
• ObjectId: every mesh drawn again through its own vertex stage with a fragment stage that writes the id in IdInfo.id as three bytes, into a single attachment, so one pixel read back says which node is under the cursor. kRequiredShaders names both. The stage samples base_color_texture and discards under the cutoff in IdInfo.mask — the material's alpha cutoff, negative when it is not masked, beside the tint's alpha — so what the scene pass throws away is thrown away here as well and a pick through a hole answers with what is behind it.
• Xray, a seventh lighting entry point: unlit.frag with F3D_NO_SURFACE_BUFFER defined, so it declares no second output at all. The x-ray stage draws its mark and its silhouette with it. Drawn unlit they wrote the surface buffer — the silhouette wherever its greater test passed, which is where the marked node is behind what the depth buffer holds — so a hidden node's normal, roughness and depth landed on top of the surface in front of it, and every screen-space effect reads that buffer as the nearest surface. kRequiredShaders names the new entry point.
• ProbePrefilter, a full-screen fragment stage that writes one face of one level of a reflection probe: the captured cube convolved by the roughness of the level, with the fixed spiral of taps and the cosine-power lobe EnvironmentMap.prefilter uses on the host, and a one-tap copy for the mirror level. kRequiredShaders names it.

• MeshLightmappedVertex, a fourth vertex stage: the standard layout with color.xy read as the vertex's place in a lightmap and the tint held at white. Every mesh stage now carries a v_lightmap_uv varying, and the lit models sample lightmap_texture (RGBM, rgb × a × 8) beside their ambient. kRequiredShaders names the new stage.

• No changes of its own; the version moves with the workspace, whose sibling constraints name a single release. The README's closing section now says what the engine around this package is.

• The physical model samples a prefiltered environment, and the composite pass applies a look.

• Cascaded directional shadows, spot shadows, screen-space ambient occlusion, a procedural sky and two-colour ambient light.
• The shared header split so a stage declares only the uniform blocks it reads: a block a shader declares but never reads is reflected at a non-zero size and binding it is a native crash.

• The engine's shader sources in GLSL, shared by every backend so that no two of them can drift, with kRequiredShaders naming the entry points a bundle must answer to.