refactor: remove the legacy full view_proj (CPU cull now relative-to-eye)

The GPU draws exclusively via the rotation-only `view_rot` + eye double-
single; the full view-projection survived only to project AABBs in the
CPU frustum-cull / scissor / LOD passes. Migrate those to the same
relative-to-eye math (project `point - eye` through `view_rot`) — pixel-
equivalent but precise at UTM scale — then drop the dead uniform:

- pipeline cull/scissor/LOD helpers take (view_rot, eye) instead of the
  full view_proj; render.rs reconstructs eye from the uniform's
  eye_high/eye_low and passes the cropped view_rot.
- Remove the `view_proj` field from the shared Uniforms struct and all six
  shader structs that only declared it for layout (none read it), and
  delete Camera::view_proj(). The struct shrinks by one mat4 on both
  sides, keeping the Rust / WGSL layouts in lock-step.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/scene/pipeline/mod.rs

@@ -1041,11 +1041,11 @@ impl Pipeline {
 
     /// Recompute pixel scissor rects for viewport-clipped wires from the current view_proj.
     /// Called every frame from prepare() because scissor pixels shift with pan/zoom.
-    pub fn compute_wire_scissors(&mut self, view_proj: glam::Mat4, clip_w: u32, clip_h: u32) {
+    pub fn compute_wire_scissors(&mut self, view_rot: glam::Mat4, eye: glam::DVec3, clip_w: u32, clip_h: u32) {
         self.wire_pixel_scissors = self
             .gpu_wires
             .iter()
-            .map(|w| project_scissor(w.vp_scissor, view_proj, clip_w, clip_h))
+            .map(|w| project_scissor(w.vp_scissor, view_rot, eye, clip_w, clip_h))
             .collect();
     }
 
@@ -1058,7 +1058,8 @@ impl Pipeline {
     pub fn compute_hatch_lod(
         &mut self,
         queue: &wgpu::Queue,
-        view_proj: glam::Mat4,
+        view_rot: glam::Mat4,
+        eye: glam::DVec3,
         clip_w: u32,
         clip_h: u32,
     ) {
@@ -1066,19 +1067,19 @@ impl Pipeline {
             return;
         };
         for (i, aabb) in batch.instance_aabbs.iter().enumerate() {
-            let skip = aabb_below_pixel(*aabb, view_proj, clip_w, clip_h, 2.0)
-                || aabb_offscreen(*aabb, view_proj, clip_w, clip_h);
+            let skip = aabb_below_pixel(*aabb, view_rot, eye, clip_w, clip_h, 2.0)
+                || aabb_offscreen(*aabb, view_rot, eye, clip_w, clip_h);
             batch.visibility[i] = if skip { 0 } else { 1 };
         }
         batch.upload_visibility(queue);
     }
 
     /// Recompute pixel scissor rects for viewport-clipped wipeouts.
-    pub fn compute_wipeout_scissors(&mut self, view_proj: glam::Mat4, clip_w: u32, clip_h: u32) {
+    pub fn compute_wipeout_scissors(&mut self, view_rot: glam::Mat4, eye: glam::DVec3, clip_w: u32, clip_h: u32) {
         self.wipeout_pixel_scissors = self
             .gpu_wipeouts
             .iter()
-            .map(|h| project_scissor(h.vp_scissor, view_proj, clip_w, clip_h))
+            .map(|h| project_scissor(h.vp_scissor, view_rot, eye, clip_w, clip_h))
             .collect();
     }
 
@@ -1086,20 +1087,20 @@ impl Pipeline {
     /// `compute_hatch_lod`'s frustum branch. No sub-pixel skip:
     /// wipeouts mask, so dropping a sub-pixel one wouldn't be wrong
     /// but also wouldn't pay off — they're usually few.
-    pub fn compute_wipeout_lod(&mut self, view_proj: glam::Mat4, clip_w: u32, clip_h: u32) {
+    pub fn compute_wipeout_lod(&mut self, view_rot: glam::Mat4, eye: glam::DVec3, clip_w: u32, clip_h: u32) {
         self.wipeout_skip_flags = self
             .gpu_wipeouts
             .iter()
-            .map(|h| aabb_offscreen(h.world_aabb, view_proj, clip_w, clip_h))
+            .map(|h| aabb_offscreen(h.world_aabb, view_rot, eye, clip_w, clip_h))
             .collect();
     }
 
     /// Recompute pixel scissor rects for viewport-clipped raster images.
-    pub fn compute_image_scissors(&mut self, view_proj: glam::Mat4, clip_w: u32, clip_h: u32) {
+    pub fn compute_image_scissors(&mut self, view_rot: glam::Mat4, eye: glam::DVec3, clip_w: u32, clip_h: u32) {
         self.image_pixel_scissors = self
             .gpu_images
             .iter()
-            .map(|i| project_scissor(i.vp_scissor, view_proj, clip_w, clip_h))
+            .map(|i| project_scissor(i.vp_scissor, view_rot, eye, clip_w, clip_h))
             .collect();
     }
 
@@ -1175,11 +1176,11 @@ impl Pipeline {
     /// projected pixel diagonal of each mesh's `world_aabb` (Phase 3.4
     /// ladder: >200 px → 0, 50–200 → 1, <50 → 2). Falls back to the
     /// nearest available lower slot when a level wasn't generated.
-    pub fn compute_mesh_lod(&mut self, view_proj: glam::Mat4, clip_w: u32, clip_h: u32) {
+    pub fn compute_mesh_lod(&mut self, view_rot: glam::Mat4, eye: glam::DVec3, clip_w: u32, clip_h: u32) {
         self.mesh_lod_levels = self
             .gpu_meshes
             .iter()
-            .map(|m| pick_mesh_lod(m, view_proj, clip_w, clip_h))
+            .map(|m| pick_mesh_lod(m, view_rot, eye, clip_w, clip_h))
             .collect();
         // Phase 2.2 — frustum-visibility flag per mesh. Cheap: same
         // 4-corner projection used for LOD selection, just answering a
@@ -1187,7 +1188,7 @@ impl Pipeline {
         self.mesh_visible = self
             .gpu_meshes
             .iter()
-            .map(|m| !aabb_offscreen(m.world_aabb, view_proj, clip_w, clip_h))
+            .map(|m| !aabb_offscreen(m.world_aabb, view_rot, eye, clip_w, clip_h))
             .collect();
     }
 
@@ -1847,11 +1848,12 @@ impl Pipeline {
 /// to the next available coarser/finer level so the mesh always renders.
 fn pick_mesh_lod(
     mesh: &MeshLodGpu,
-    view_proj: glam::Mat4,
+    view_rot: glam::Mat4,
+    eye: glam::DVec3,
     clip_w: u32,
     clip_h: u32,
 ) -> usize {
-    let diag_px = aabb_diagonal_pixels(mesh.world_aabb, view_proj, clip_w, clip_h);
+    let diag_px = aabb_diagonal_pixels(mesh.world_aabb, view_rot, eye, clip_w, clip_h);
     let target = if diag_px > 200.0 {
         0
     } else if diag_px > 50.0 {
@@ -1870,7 +1872,8 @@ fn pick_mesh_lod(
 
 fn aabb_diagonal_pixels(
     aabb: [f32; 4],
-    view_proj: glam::Mat4,
+    view_rot: glam::Mat4,
+    eye: glam::DVec3,
     clip_w: u32,
     clip_h: u32,
 ) -> f32 {
@@ -1881,10 +1884,10 @@ fn aabb_diagonal_pixels(
     let w = clip_w as f32;
     let h = clip_h as f32;
     let corners = [
-        view_proj.project_point3(glam::Vec3::new(x0, y0, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x1, y0, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x0, y1, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x1, y1, 0.0)),
+        view_rot.project_point3((glam::DVec3::new(x0 as f64, y0 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x1 as f64, y0 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x0 as f64, y1 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x1 as f64, y1 as f64, 0.0) - eye).as_vec3()),
     ];
     let mut min_px = f32::INFINITY;
     let mut max_px = f32::NEG_INFINITY;
@@ -1916,7 +1919,8 @@ fn aabb_diagonal_pixels(
 /// extents` for this reason; meshes already store an absolute rect.
 fn aabb_offscreen(
     aabb: [f32; 4],
-    view_proj: glam::Mat4,
+    view_rot: glam::Mat4,
+    eye: glam::DVec3,
     clip_w: u32,
     clip_h: u32,
 ) -> bool {
@@ -1927,10 +1931,10 @@ fn aabb_offscreen(
     let w = clip_w as f32;
     let h = clip_h as f32;
     let corners = [
-        view_proj.project_point3(glam::Vec3::new(x0, y0, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x1, y0, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x0, y1, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x1, y1, 0.0)),
+        view_rot.project_point3((glam::DVec3::new(x0 as f64, y0 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x1 as f64, y0 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x0 as f64, y1 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x1 as f64, y1 as f64, 0.0) - eye).as_vec3()),
     ];
     let mut min_px = f32::INFINITY;
     let mut max_px = f32::NEG_INFINITY;
@@ -1958,7 +1962,8 @@ fn aabb_offscreen(
 /// draw calls that wouldn't contribute a visible pixel.
 fn aabb_below_pixel(
     aabb: [f32; 4],
-    view_proj: glam::Mat4,
+    view_rot: glam::Mat4,
+    eye: glam::DVec3,
     clip_w: u32,
     clip_h: u32,
     threshold_px: f32,
@@ -1970,10 +1975,10 @@ fn aabb_below_pixel(
     let w = clip_w as f32;
     let h = clip_h as f32;
     let corners = [
-        view_proj.project_point3(glam::Vec3::new(x0, y0, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x1, y0, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x0, y1, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x1, y1, 0.0)),
+        view_rot.project_point3((glam::DVec3::new(x0 as f64, y0 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x1 as f64, y0 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x0 as f64, y1 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x1 as f64, y1 as f64, 0.0) - eye).as_vec3()),
     ];
     let mut min_px = f32::INFINITY;
     let mut max_px = f32::NEG_INFINITY;
@@ -1996,7 +2001,8 @@ fn aabb_below_pixel(
 /// the projection collapses (off-screen, behind camera).
 fn project_scissor(
     rect: Option<[f32; 4]>,
-    view_proj: glam::Mat4,
+    view_rot: glam::Mat4,
+    eye: glam::DVec3,
     clip_w: u32,
     clip_h: u32,
 ) -> Option<[u32; 4]> {
@@ -2004,10 +2010,10 @@ fn project_scissor(
     let w = clip_w as f32;
     let h = clip_h as f32;
     let corners = [
-        view_proj.project_point3(glam::Vec3::new(x0, y0, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x1, y0, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x0, y1, 0.0)),
-        view_proj.project_point3(glam::Vec3::new(x1, y1, 0.0)),
+        view_rot.project_point3((glam::DVec3::new(x0 as f64, y0 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x1 as f64, y0 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x0 as f64, y1 as f64, 0.0) - eye).as_vec3()),
+        view_rot.project_point3((glam::DVec3::new(x1 as f64, y1 as f64, 0.0) - eye).as_vec3()),
     ];
     let px: Vec<f32> = corners.iter().map(|c| (c.x + 1.0) * 0.5 * w).collect();
     let py: Vec<f32> = corners.iter().map(|c| (1.0 - c.y) * 0.5 * h).collect();

src/scene/pipeline/uniforms.rs

@@ -4,11 +4,6 @@ use iced::Rectangle;
 #[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
 #[repr(C)]
 pub struct Uniforms {
-    /// Full view-projection (with translation) — GPU rendering no longer uses
-    /// this; it remains for the CPU-side frustum-cull / scissor / LOD passes
-    /// that project offset-relative AABBs to screen. The GPU draws via the
-    /// relative-to-eye `view_rot` + `eye_high`/`eye_low` below.
-    pub view_proj: glam::Mat4,
     pub viewport_size: [f32; 2],
     /// World units per screen pixel at the current zoom. Used by the
     /// hatch shader to substitute solid fill when pattern line spacing
@@ -54,7 +49,6 @@ impl Uniforms {
         };
         let (eye_high, eye_low) = camera.eye_high_low();
         Self {
-            view_proj: camera.view_proj(bounds),
             viewport_size: [bounds.width, bounds.height],
             world_per_pixel,
             lwdisplay_enable: if lwdisplay_enable { 1.0 } else { 0.0 },

src/scene/view/camera.rs

@@ -91,28 +91,6 @@ impl Camera {
 
     // ── Projection matrices ────────────────────────────────────────────────
 
-    pub fn view_proj(&self, bounds: Rectangle) -> Mat4 {
-        let aspect = bounds.width / bounds.height;
-
-        // Up vector: use the rotation to find which world direction is "up"
-        // in the current camera frame.
-        let up_dir = self.rotation * Vec3::Y;
-
-        let view = Mat4::look_at_rh(self.eye(), self.target.as_vec3(), up_dir);
-        let proj = match self.projection {
-            Projection::Perspective => {
-                Mat4::perspective_rh(self.fov_y, aspect, self.distance * 0.001, self.distance * 1000.0)
-            }
-            Projection::Orthographic => {
-                let h = self.ortho_size();
-                let w = h * aspect;
-                let (near, far) = self.ortho_depth_range();
-                Mat4::orthographic_rh(-w, w, -h, h, near, far)
-            }
-        };
-        OPENGL_TO_WGPU * proj * view
-    }
-
     /// Orthographic near/far that CENTRE the target plane at ndc-z ≈ 0.5.
     ///
     /// The draw-order depth bias shifts clip-z by ±`DRAW_ORDER_BIAS` (0.001).

src/scene/view/render.rs

@@ -305,13 +305,20 @@ impl shader::Primitive for Primitive {
             // refreshed every frame it's present, so a drag never re-uploads
             // the resident base wire buffer.
             inner.upload_preview_wires(device, &vp.preview_wires[..], &vp.draw_depths);
-            let vproj = vp.uniforms.view_proj;
-            inner.compute_wire_scissors(vproj, clip_size.width, clip_size.height);
-            inner.compute_wipeout_scissors(vproj, clip_size.width, clip_size.height);
-            inner.compute_image_scissors(vproj, clip_size.width, clip_size.height);
-            inner.compute_hatch_lod(queue, vproj, clip_size.width, clip_size.height);
-            inner.compute_wipeout_lod(vproj, clip_size.width, clip_size.height);
-            inner.compute_mesh_lod(vproj, clip_size.width, clip_size.height);
+            // Cull / scissor / LOD project AABBs relative-to-eye (matching the
+            // GPU's RTE path) so the math stays precise at UTM-scale coords.
+            let view_rot = vp.uniforms.view_rot;
+            let eye = glam::DVec3::new(
+                vp.uniforms.eye_high[0] as f64 + vp.uniforms.eye_low[0] as f64,
+                vp.uniforms.eye_high[1] as f64 + vp.uniforms.eye_low[1] as f64,
+                vp.uniforms.eye_high[2] as f64 + vp.uniforms.eye_low[2] as f64,
+            );
+            inner.compute_wire_scissors(view_rot, eye, clip_size.width, clip_size.height);
+            inner.compute_wipeout_scissors(view_rot, eye, clip_size.width, clip_size.height);
+            inner.compute_image_scissors(view_rot, eye, clip_size.width, clip_size.height);
+            inner.compute_hatch_lod(queue, view_rot, eye, clip_size.width, clip_size.height);
+            inner.compute_wipeout_lod(view_rot, eye, clip_size.width, clip_size.height);
+            inner.compute_mesh_lod(view_rot, eye, clip_size.width, clip_size.height);
             if vp.show_viewcube {
                 inner.viewcube.upload(
                     queue,
@@ -743,9 +750,7 @@ impl Scene {
         };
         let mut uniforms =
             Uniforms::new(&inst.camera, full_bounds, self.document.header.lineweight_display);
-        uniforms.view_proj = crop_view_proj(uniforms.view_proj, uo, vo, us, vs);
-        // The RTE matrix is a view-projection too, so the same clip-space crop
-        // applies — keep it in lock-step with view_proj for tiled / sub-rect panes.
+        // Crop the rotation-only RTE view-projection to the visible sub-rect.
         uniforms.view_rot = crop_view_proj(uniforms.view_rot, uo, vo, us, vs);
         uniforms.viewport_size = [visible_w, visible_h];
         uniforms.flat_shade = if flags.flat_shade { 1.0 } else { 0.0 };

src/shaders/face3d.wgsl

@@ -5,7 +5,6 @@
 //   color     [f32; 4]   offset 12   16 B
 
 struct Uniforms {
-    view_proj:           mat4x4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/hatch.wgsl

@@ -13,7 +13,6 @@
 // ── Group 0: frame uniforms (shared) ──────────────────────────────────────
 
 struct Uniforms {
-    view_proj:           mat4x4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/hatch_batched.wgsl

@@ -18,7 +18,6 @@
 // ── Group 0: shared frame uniforms (matches hatch.wgsl) ──────────────────
 
 struct Uniforms {
-    view_proj:           mat4x4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/image.wgsl

@@ -4,7 +4,6 @@
 // ── Bind group 0: shared projection uniforms ─────────────────────────────────
 // Must match the shared `Uniforms` struct (scene::pipeline::uniforms, 112 B).
 struct Uniforms {
-    view_proj:          mat4x4<f32>,
     viewport_size:      vec2<f32>,
     world_per_pixel:    f32,
     lwdisplay_enable:   f32,

src/shaders/mesh.wgsl

@@ -10,7 +10,6 @@
 //     flat shade (FlatShaded).
 
 struct Uniforms {
-    view_proj:           mat4x4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/wire.wgsl

@@ -14,7 +14,6 @@
 //   • pat0/pat1 encode up to 8 elements: positive=dash, negative=gap.
 
 struct Uniforms {
-    view_proj:        mat4x4<f32>,
     viewport_size:    vec2<f32>,
     world_per_pixel:  f32,
     // LWDISPLAY toggle: 0.0 = force 1 px (half_width 0.5), 1.0 = use the