bklronin
254 lines
11 KiB
Markdown
254 lines
11 KiB
Markdown
# Realistic Render View — Implementation Plan
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## Context
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Add a **"Render"** feature to Fluency CAD that opens a separate window for photorealistic rendering of the selected component or assembly (like KeyShot/Cacles).
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**Constraints:**
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- Open in a **new window** — don't clutter the workspace
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- **Keep existing OCCRenderer** for the interactive 3D viewport — untouched
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- Render backend must be a **separate, swappable module** so we can change the renderer later
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- Use **Mitsuba 3** as the initial backend (`pip install mitsuba`, ~50MB)
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---
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## Architecture
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```
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┌─────────────────────────────────────────────────────────┐
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│ Main Fluency Window (existing OCCRenderer — untouched) │
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│ │
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│ [Select body/assembly] → [Click "Render"] │
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│ │ │
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│ ▼ │
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│ ┌─────────────────────────────────────┐ │
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│ │ RenderWindow (separate QMainWindow)│ │
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│ │ │ │
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│ │ ┌───────────────────────────────┐ │ │
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│ │ │ RenderBackend (ABC) │ │ │
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│ │ │ ├─ MitsubaBackend ← current │ │ │
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│ │ │ ├─ (future: BlenderBackend) │ │ │
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│ │ │ └─ (future: CyclesBackend) │ │ │
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│ │ └───────────────────────────────┘ │ │
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│ │ │ │\n│ │ [Image preview] [Progress bar] │ │
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│ │ [Material ▾] [Quality ▾] [Render] │ │
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│ │ [Export PNG] │ │
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│ └─────────────────────────────────────┘ │
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└─────────────────────────────────────────────────────────┘
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```
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### Swappable Backend Interface
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```python
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from abc import ABC, abstractmethod
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from dataclasses import dataclass
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import numpy as np
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@dataclass
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class RenderMaterial:
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name: str
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color: tuple[float, float, float] = (0.7, 0.7, 0.7)
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metallic: float = 0.0 # 0.0–1.0
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roughness: float = 0.5 # 0.0–1.0
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bsdf_type: str = "diffuse" # diffuse | roughconductor | roughdielectric | plastic
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@dataclass
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class RenderCamera:
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origin: tuple[float, float, float] = (100, 100, 100)
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target: tuple[float, float, float] = (0, 0, 0)
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up: tuple[float, float, float] = (0, 0, 1)
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fov: float = 45.0
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@dataclass
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class RenderSettings:
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width: int = 1920
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height: int = 1080
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spp: int = 256 # samples per pixel
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max_depth: int = 8 # path tracer bounces
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class RenderBackend(ABC):
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"""Swap this to change the rendering engine."""
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@abstractmethod
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def render(self, obj_path: str, material: RenderMaterial,
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camera: RenderCamera, settings: RenderSettings) -> np.ndarray: ...
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@abstractmethod
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def render_preview(self, obj_path: str, material: RenderMaterial,
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camera: RenderCamera, settings: RenderSettings) -> np.ndarray: ...
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@abstractmethod
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def name(self) -> str: ...
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```
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Switching backends later = write a new class implementing `RenderBackend`. One import change.
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---
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## Mitsuba 3 Backend
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### Why Mitsuba
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| Feature | Status |
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|---------|--------|
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| `pip install mitsuba` | Single install, no system deps |
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| True path tracing | GI, caustics, spectral rendering |
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| PBR materials | `roughconductor`, `roughdielectric`, `diffuse`, `plastic` |
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| Python dict API | Build scenes programmatically, no XML |
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| CPU + GPU backends | `scalar_rgb` (CPU), `cuda_rgb` (NVIDIA) |
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| Output formats | PNG, EXR (HDR) with tonemapping |
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### OCC → OBJ Conversion Path
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```python
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from OCP.BRepMesh import BRepMesh_IncrementalMesh
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from OCP.StlAPI import StlAPI_Writer
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from OCP.BRep import BRep_Builder
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import tempfile, os
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def occ_shape_to_obj(shape, obj_path: str, linear_deflection: float = 0.1):
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"""Tessellate OCC shape and write as OBJ for Mitsuba."""
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tess = BRepMesh_IncrementalMesh(shape, linear_deflection, False, 0.5, True)
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tess.Perform()
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# Write STL (reliable), then convert to OBJ via trimesh or direct
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writer = StlAPI_Writer()
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writer.SetASCIIMode(False)
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stl_path = obj_path.replace(".obj", ".stl")
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writer.Write(shape, stl_path)
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# Mitsuba can read STL directly, or we convert to OBJ
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return stl_path
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```
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### Mitsuba Scene Construction
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```python
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import mitsuba as mi
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mi.set_variant("scalar_rgb")
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def build_scene(mesh_path: str, material: RenderMaterial,
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camera: RenderCamera, settings: RenderSettings) -> mi.Scene:
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# Map our material to Mitsuba BSDF
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bsdf_map = {
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"diffuse": {"type": "diffuse", "reflectance": {"type": "rgb", "value": material.color}},
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"roughconductor": {
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"type": "roughconductor",
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"material": "copper", # or铝, 钢, etc.
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"alpha": material.roughness,
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},
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"roughdielectric": {
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"type": "roughdielectric",
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"int_ior": 1.5,
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"alpha": material.roughness,
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},
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"plastic": {
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"type": "plastic",
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"diffuse_reflectance": {"type": "rgb", "value": material.color},
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"int_ior": 1.5,
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},
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}
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return mi.load_dict({
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"type": "scene",
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"integrator": {"type": "path", "max_depth": settings.max_depth},
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"sensor": {
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"type": "perspective",
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"fov": camera.fov,
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"to_world": mi.ScalarTransform4f.look_at(
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origin=camera.origin, target=camera.target, up=camera.up
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),
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"film": {"type": "hdrfilm", "width": settings.width, "height": settings.height},
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"sampler": {"type": "independent", "sample_count": settings.spp},
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},
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"emitter": {"type": "constant"},
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"shape": {
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"type": "stl", # or "obj"
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"filename": mesh_path,
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"bsdf": bsdf_map.get(material.bsdf_type, bsdf_map["diffuse"]),
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},
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})
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```
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---
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## Files to Create/Modify
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| File | Action | Description |
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|------|--------|-------------|
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| `src/fluency/rendering/render_backend.py` | **NEW** | Abstract `RenderBackend`, `RenderMaterial`, `RenderCamera`, `RenderSettings` |
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| `src/fluency/rendering/mitsuba_backend.py` | **NEW** | `MitsubaBackend(RenderBackend)` implementation |
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| `src/fluency/rendering/occ_to_mesh.py` | **NEW** | OCC `TopoDS_Shape` → STL/OBJ tessellation |
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| `src/fluency/rendering/material_presets.py` | **NEW** | Preset library: Steel, Aluminum, Brass, Chrome, Plastic, Rubber, Wood |
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| `src/fluency/ui/render_window.py` | **NEW** | `RenderWindow(QMainWindow)` — image preview, material/quality controls, render/export |
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| `src/fluency/ui/main_window.py` | MODIFY | Add "Render" button → get selected shapes → open `RenderWindow` |
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---
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## UI: RenderWindow
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```
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┌──────────────────────────────────────────┐
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│ Render — [Part Name] [─][□][×] │
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├──────────────────────────────────────────┤
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│ │
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│ ┌──────────────────────────────────┐ │
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│ │ │ │
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│ │ Rendered Image Preview │ │
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│ │ (QLabel with QPixmap) │ │
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│ │ │ │
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│ └──────────────────────────────────┘ │
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│ │
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│ Material: [Steel ▾] │
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│ Quality: [256 SPP ▾] │
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│ Resolution: [1920×1080 ▾] │
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│ │
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│ [▶ Render] [⏹ Cancel] [💾 Export PNG] │
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│ │
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│ ████████████████░░░░░░ 65% (23s left) │
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└──────────────────────────────────────────┘
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```
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- **Preview**: progressive refinement (low SPP first, then ramp)
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- **Cancel**: kill Mitsuba render thread
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- **Export**: save to PNG/EXR
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---
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## Material Presets
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| Preset | Color | Metallic | Roughness | BSDF |
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|--------|-------|----------|-----------|------|
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| Brushed Steel | (0.65, 0.67, 0.72) | 0.9 | 0.35 | roughconductor |
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| Polished Chrome | (0.8, 0.8, 0.8) | 1.0 | 0.05 | roughconductor |
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| Brushed Aluminum | (0.75, 0.75, 0.75) | 0.85 | 0.25 | roughconductor |
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| Copper | (0.95, 0.64, 0.54) | 0.95 | 0.15 | roughconductor |
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| Gold | (1.0, 0.76, 0.33) | 1.0 | 0.1 | roughconductor |
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| Blackened Steel | (0.15, 0.15, 0.17) | 0.8 | 0.4 | roughconductor |
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| Matte Plastic | (0.2, 0.5, 0.8) | 0.0 | 0.6 | plastic |
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| Glossy Plastic | (0.2, 0.5, 0.8) | 0.0 | 0.1 | plastic |
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| White Nylon | (0.85, 0.85, 0.83) | 0.0 | 0.45 | plastic |
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| Black ABS | (0.05, 0.05, 0.05) | 0.0 | 0.35 | plastic |
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| Red PA12 | (0.75, 0.08, 0.08) | 0.0 | 0.4 | plastic |
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| Rubber | (0.1, 0.1, 0.1) | 0.0 | 0.9 | diffuse |
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| Ceramic White | (0.92, 0.91, 0.88) | 0.0 | 0.15 | dielectric |
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| Glass | (0.95, 0.95, 0.95) | 0.0 | 0.0 | dielectric |
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| Wood | (0.6, 0.4, 0.2) | 0.0 | 0.7 | diffuse |
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**Note:** Mitsuba pip installs don't include spectral metal data files (iron.spd, copper.spd, etc.), so metal presets use `material="none"` with `specular_reflectance` set to the metal color instead.
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---
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## Risks & Mitigations
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| Risk | Mitigation |
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|------|-----------|
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| Mitsuba not installed | Graceful error: "pip install mitsuba" shown in UI |
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| Slow CPU rendering | Default to low SPP (64) for preview; offer GPU variant if CUDA available |
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| Large meshes slow to tessellate | Progress indicator; optional mesh decimation |
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| Mitsuba STL/OCC compatibility | Test tessellation quality; tune `linear_deflection` |
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---
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## Estimated Effort
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- **Phase 1** (abstract backend + OCC→mesh + Mitsuba impl): ~4-6 hours
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- **Phase 2** (render window UI + material presets): ~3-4 hours
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- **Phase 3** (polish, export, swap test): ~2-3 hours
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- **Total**: ~9-13 hours
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