refactor: cinematic render — linear keyframes, 3 segments, 250 frames, white bg

Changes per user feedback:
- Keyframe interpolation: BEZIER → LINEAR (all fcurves set to LINEAR)
- Removed segment 4 (closeup) — now 3 segments only
- Frame count: 480 → 250 (10 seconds at 25fps)
- FPS: 24 → 25
- Easing removed — pure linear interpolation between segment params
- White background by default (World node Color = white)
- Transparent bg still available as override

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/render_blender.py

@@ -563,8 +563,8 @@ def render_cinematic_to_file(
     import time
 
     # Cinematic parameters are fixed
-    frame_count = 480
+    frame_count = 250
-    fps = 24
+    fps = 25
 
     blender_bin = find_blender()
     if not blender_bin:

render-worker/scripts/cinematic_render.py

@@ -249,14 +249,11 @@ def _apply_material_library(parts, mat_lib_path, mat_map, part_names_ordered=Non
 
 # ── Cinematic camera animation ───────────────────────────────────────────────
 
-TOTAL_FRAMES = 480
+TOTAL_FRAMES = 250
-SEGMENT_LENGTH = 120  # frames per segment
+NUM_SEGMENTS = 3
+SEGMENT_LENGTH = TOTAL_FRAMES // NUM_SEGMENTS  # ~83 frames per segment
 
-# Segment definitions: (start_azimuth_offset, end_azimuth_offset,
+# 3 segments (no closeup): establishing, detail sweep, crane up
-#                        start_elevation, end_elevation,
-#                        start_dist_factor, end_dist_factor,
-#                        start_lens, end_lens,
-#                        use_dof)
 SEGMENTS = [
     # Segment 1: Establishing shot — orbit 45deg, push in, 50mm
     {
@@ -282,25 +279,9 @@ SEGMENTS = [
         "lens_start": 35.0, "lens_end": 35.0,
         "dof": False,
     },
-    # Segment 4: Hero close — push in, settle down
-    {
-        "az_start": 120.0, "az_end": 120.0,
-        "el_start": 35.0, "el_end": 25.0,
-        "dist_start": 3.0, "dist_end": 2.2,
-        "lens_start": 65.0, "lens_end": 65.0,
-        "dof": False,
-    },
 ]
 
 
-def _ease_in_out(t: float) -> float:
-    """Cubic ease in-out, t in [0, 1]."""
-    if t < 0.5:
-        return 4.0 * t * t * t
-    else:
-        return 1.0 - (-2.0 * t + 2.0) ** 3 / 2.0
-
-
 def _lerp(a: float, b: float, t: float) -> float:
     """Linear interpolation."""
     return a + (b - a) * t
@@ -322,21 +303,10 @@ def _get_segment_params(frame: int, bsphere_radius: float):
 
     Returns (azimuth_deg, elevation_deg, distance, lens_mm, use_dof).
     """
-    # Determine which segment (0-3) and local t (0-1)
+    # Determine which segment and local t (0-1) — linear interpolation
     seg_index = min((frame - 1) // SEGMENT_LENGTH, len(SEGMENTS) - 1)
     local_frame = (frame - 1) - seg_index * SEGMENT_LENGTH
-    raw_t = local_frame / max(SEGMENT_LENGTH - 1, 1)
+    t = local_frame / max(SEGMENT_LENGTH - 1, 1)  # linear, no easing
-
-    # Apply easing: smooth start for segment 1, smooth stop for segment 4,
-    # ease-in-out for segments 2 and 3
-    if seg_index == 0:
-        # Smooth start: ease-out (decelerate into motion)
-        t = _ease_in_out(raw_t)
-    elif seg_index == 3:
-        # Smooth stop: ease-in-out with emphasis on deceleration
-        t = _ease_in_out(raw_t)
-    else:
-        t = _ease_in_out(raw_t)
 
     seg = SEGMENTS[seg_index]
 
@@ -409,7 +379,21 @@ def _setup_cinematic_camera(parts, bbox_center, bsphere_radius, total_frames):
         cam_obj.data.dof.keyframe_insert(data_path="focus_distance", frame=frame)
         cam_obj.data.dof.keyframe_insert(data_path="aperture_fstop", frame=frame)
 
-    print(f"[cinematic_render] camera keyframed: {total_frames} frames across 4 segments")
+    # Set all keyframes to LINEAR interpolation (no bezier smoothing)
+    if cam_obj.animation_data and cam_obj.animation_data.action:
+        for fcurve in cam_obj.animation_data.action.fcurves:
+            for kp in fcurve.keyframe_points:
+                kp.interpolation = 'LINEAR'
+    if cam_obj.data.animation_data and cam_obj.data.animation_data.action:
+        for fcurve in cam_obj.data.animation_data.action.fcurves:
+            for kp in fcurve.keyframe_points:
+                kp.interpolation = 'LINEAR'
+    if cam_obj.data.dof.animation_data and cam_obj.data.dof.animation_data.action:
+        for fcurve in cam_obj.data.dof.animation_data.action.fcurves:
+            for kp in fcurve.keyframe_points:
+                kp.interpolation = 'LINEAR'
+
+    print(f"[cinematic_render] camera keyframed: {total_frames} frames across {len(SEGMENTS)} segments (LINEAR interpolation)", flush=True)
     return cam_obj
 
 
@@ -828,13 +812,25 @@ def main():
     scene.render.resolution_percentage = 100
     scene.render.image_settings.file_format = 'PNG'
 
-    # ── Transparent background ───────────────────────────────────────────────
+    # ── White background (default for cinematic) ────────────────────────────
+    # Set world to white unless template provides its own
+    if not template_path:
+        world = bpy.data.worlds.new("CinematicWorld")
+        scene.world = world
+        world.use_nodes = True
+        bg_node = world.node_tree.nodes.get("Background")
+        if bg_node:
+            bg_node.inputs["Color"].default_value = (1.0, 1.0, 1.0, 1.0)
+            bg_node.inputs["Strength"].default_value = 1.0
+        print("[cinematic_render] white background set", flush=True)
+
+    # ── Transparent background (override if requested) ────────────────────
     if bg_color or transparent_bg:
         scene.render.film_transparent = True
         if bg_color:
-            print(f"[cinematic_render] film_transparent=True for FFmpeg bg_color compositing ({bg_color})")
+            print(f"[cinematic_render] film_transparent=True for FFmpeg bg_color compositing ({bg_color})", flush=True)
         else:
-            print("[cinematic_render] transparent_bg enabled (alpha PNG frames)")
+            print("[cinematic_render] transparent_bg enabled (alpha PNG frames)", flush=True)
 
     # ── Persistent data (Cycles BVH caching between frames) ──────────────────
     scene.render.use_persistent_data = True