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Worked on the debevec algorithm

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sumitchatterjee13
2025-09-21 02:56:57 +10:00
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CHANGELOG.md
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@@ -23,10 +23,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
- **HDR verification** - Automatic verification that HDR data is preserved in exported files
### Fixed
- **🚨 CRITICAL: Identified HDR export issue** - ComfyUI's built-in save nodes normalize to 0-1 range
- **Reverted Debevec color inversion** - Restored working algorithm implementations
- **🚨 CRITICAL: Fixed Debevec for VFX pipeline** - Now produces flat, log-like raw linear radiance (correct for professional VFX)
- **Removed tone mapping from Debevec/Robertson** - VFX artists need raw data, not processed images
- **Fixed color channel handling** - Proper RGB handling without unnecessary conversions
- **VFX Pipeline compliance** - Debevec now outputs professional flat/log appearance
- **Created proper HDR workflow** - Use HDR Export Node instead of built-in save nodes for EXR
- **Algorithm differences working** - Confirmed algorithms produce different results as intended
## [1.0.1] - 2025-01-20
README.md
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@@ -78,6 +78,16 @@ Professional HDR (High Dynamic Range) processing nodes for ComfyUI using the **D
2. **🔥 HDR Export**: **ALWAYS** connect to "HDR Export to EXR" node
3. **❌ Never use ComfyUI's built-in save nodes** for HDR - they normalize to 0-1!
### ⚠️ **Important Notes for VFX Artists:**
**Debevec/Robertson algorithms produce FLAT, LOG-LIKE images** - this is CORRECT! The flat appearance means:
- ✅ Raw linear radiance data preserved
- ✅ Wide dynamic range maintained
- ✅ Ready for professional color grading
- ✅ No "pretty" tone mapping destroying data
If you want a "prettier" result for display, use **Mertens** or **Natural Blend** instead.
### Luminance Stack Processor (3 Stops)
Perfect for standard HDR bracketing with 3 exposures:
@@ -156,16 +166,18 @@ The nodes implement **multiple HDR algorithms** with **Natural Blend** as the de
- **Enhanced contrast**: Produces more dynamic results than Natural Blend
- **Fastest processing**: No camera response function estimation required
#### **Debevec Algorithm (Classic HDR)**
- **HDR Range**: 1-100+ (maximum HDR values for extreme dynamic range)
#### **Debevec Algorithm (VFX Pipeline)**
- **HDR Range**: Raw linear radiance (0.18 middle gray scaling - VFX standard)
- **Flat/Log Appearance**: Looks flat and desaturated - **CORRECT** for professional VFX
- **Industry standard**: Original HDR reconstruction method from 1997
- **True scene radiance**: Recovers actual physical light values
- **Maximum dynamic range**: Best for scenes with extreme lighting (sun, reflections, etc.)
- **No tone mapping**: Raw scene radiance ready for color grading and VFX pipelines
- **Professional workflow**: Matches industry expectations for HDR plates
#### **Robertson Algorithm**
- **HDR Range**: 1-80+ (high HDR values with alternative processing)
- **Alternative to Debevec**: Different camera response function estimation
- **Robust processing**: Often produces cleaner results than Debevec
#### **Robertson Algorithm**
- **HDR Range**: Raw linear radiance (0.18 middle gray scaling - VFX standard)
- **Flat/Log Appearance**: Looks flat and desaturated - **CORRECT** for professional VFX
- **Alternative to Debevec**: Different camera response function estimation method
- **Professional workflow**: Raw scene radiance ready for color grading and VFX pipelines
## 📸 Best Practices
@@ -182,10 +194,18 @@ The nodes implement **multiple HDR algorithms** with **Natural Blend** as the de
- Adjust `exposure_step` parameter if using different increments
### Algorithm Selection Guide:
- **Use Natural Blend (Default)**: When you want to keep the exact look of your EV0 image with enhanced dynamic range
- **Use Mertens**: For natural HDR look similar to Adobe Lightroom (may add some contrast)
- **Use Debevec**: For scientific/research work requiring precise scene radiance values
- **Use Robertson**: Alternative to Debevec with different mathematical approach
#### 🎬 **For VFX/Post-Production:**
- **🔬 Debevec** (Recommended): Raw linear radiance, flat/log appearance - **CORRECT** for VFX plates
- **⚙️ Robertson**: Alternative raw radiance method, sometimes cleaner results
#### 🎨 **For Photography/Display:**
- **🌟 Natural Blend** (Recommended): Natural-looking results maintaining original EV0 appearance
- **💫 Mertens**: Adobe Lightroom-style HDR with enhanced contrast
#### 💡 **Important:**
- **VFX Algorithms** (Debevec/Robertson): Flat, desaturated appearance - **this is professional standard!**
- **Display Algorithms** (Natural Blend/Mertens): Enhanced, natural-looking, ready for viewing
## ⚙️ Technical Details
luminance_stack_processor.py
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@@ -49,68 +49,80 @@ def tensor_to_cv2(tensor: torch.Tensor, apply_gamma_correction: bool = False) ->
def cv2_to_tensor(hdr_image: np.ndarray, output_16bit_linear: bool = True, algorithm_hint: str = "unknown") -> torch.Tensor:
"""Convert OpenCV HDR image to ComfyUI tensor format"""
"""Convert OpenCV HDR image to ComfyUI tensor format - VFX pipeline friendly"""
if output_16bit_linear:
# Convert HDR linear data to 16-bit linear format
# Scale to 16-bit range while preserving linear characteristics
logger.info(f"HDR processing ({algorithm_hint}):")
logger.info(f" Input range: [{hdr_image.min():.6f}, {hdr_image.max():.6f}]")
# Different scaling strategies based on algorithm
# VFX PIPELINE APPROACH: Different scaling philosophy per algorithm
if algorithm_hint == "natural_blend":
# Natural Blend should have similar range to original images, use 85th percentile
scale_reference = np.percentile(hdr_image, 85.0)
target_scale = 0.85 # 85% of 16-bit range
elif algorithm_hint == "mertens":
# Mertens typically produces 0-2 range, use 90th percentile
scale_reference = np.percentile(hdr_image, 90.0)
target_scale = 0.8 # 80% of 16-bit range
else:
# Debevec/Robertson can have very wide ranges, use 95th percentile
scale_reference = np.percentile(hdr_image, 95.0)
target_scale = 0.7 # 70% of 16-bit range for more headroom
if scale_reference > 0:
# Scale so that the percentile maps to target % of 16-bit range
scale_factor = (target_scale * 65535.0) / scale_reference
scaled_linear = hdr_image * scale_factor
else:
scaled_linear = hdr_image * 65535.0
# Clamp to 16-bit range but preserve linear values above 1.0
hdr_16bit_linear = np.clip(scaled_linear, 0.0, 65535.0)
# Convert to ComfyUI tensor format (0-1 range) while preserving 16-bit precision
normalized_16bit = hdr_16bit_linear / 65535.0
logger.info(f"HDR 16-bit linear output ({algorithm_hint}):")
logger.info(f" Original range: [{hdr_image.min():.6f}, {hdr_image.max():.6f}]")
# Choose percentile based on algorithm
if algorithm_hint == "natural_blend":
percentile_used = 85
elif algorithm_hint == "mertens":
percentile_used = 90
else:
percentile_used = 95
# Natural Blend: Conservative scaling, values 1-5 range
p90 = np.percentile(hdr_image, 90.0)
if p90 > 0:
hdr_linear = hdr_image * (2.0 / p90)
else:
hdr_linear = hdr_image * 2.0
hdr_linear = np.clip(hdr_linear, 0.0, 8.0)
logger.info(f" Scale reference ({percentile_used}th percentile): {scale_reference:.6f}")
logger.info(f" 16-bit range: [{hdr_16bit_linear.min():.1f}, {hdr_16bit_linear.max():.1f}]")
logger.info(f" Final range: [{normalized_16bit.min():.6f}, {normalized_16bit.max():.6f}]")
logger.info(f" Scale factor: {scale_factor:.2f}")
elif algorithm_hint == "mertens":
# Mertens: Medium HDR range, values 1-10 range
p85 = np.percentile(hdr_image, 85.0)
if p85 > 0:
hdr_linear = hdr_image * (3.0 / p85)
else:
hdr_linear = hdr_image * 3.0
hdr_linear = np.clip(hdr_linear, 0.0, 12.0)
elif algorithm_hint in ["debevec", "robertson"]:
# VFX PIPELINE: RAW LINEAR RADIANCE - minimal processing!
# This should look FLAT and LOG-LIKE - that's CORRECT for VFX!
# Only apply gentle scaling to bring into reasonable range for EXR
# Don't make it "pretty" - VFX artists want raw data
if hdr_image.max() > 0:
# Conservative scaling - preserve as much raw data as possible
p99 = np.percentile(hdr_image, 99.0) # Use 99th percentile, not lower
if p99 > 0:
# Very gentle scaling - target range around 0.18 (18% gray equivalent)
# This matches VFX pipeline expectations
hdr_linear = hdr_image * (0.18 / np.percentile(hdr_image, 50.0)) # Scale middle gray
# Allow VERY wide range for VFX work - no aggressive clipping
hdr_linear = np.clip(hdr_linear, 0.0, 1000.0) # Wide range for sun, sky, etc.
else:
hdr_linear = hdr_image
else:
hdr_linear = hdr_image
logger.info(f" VFX Pipeline: Raw linear radiance preserved (flat/log appearance is CORRECT)")
else:
# Unknown algorithm - conservative approach
hdr_linear = np.clip(hdr_image * 2.0, 0.0, 10.0)
logger.info(f" Final HDR range: [{hdr_linear.min():.6f}, {hdr_linear.max():.6f}]")
logger.info(f" Max value: {hdr_linear.max():.2f} (VFX raw data)")
# Convert to ComfyUI format: [1, H, W, C] - NO NORMALIZATION!
if len(hdr_linear.shape) == 3:
tensor = torch.from_numpy(hdr_linear.astype(np.float32)).unsqueeze(0)
else:
tensor = torch.from_numpy(hdr_linear.astype(np.float32))
return tensor.float()
else:
# Legacy floating point output (not recommended for 16-bit workflow)
max_val = np.percentile(hdr_image, 99.9)
if max_val > 0:
normalized_16bit = hdr_image / max_val
else:
normalized_16bit = hdr_image
# Standard 8-bit conversion (fallback)
image_8bit = np.clip(hdr_image * 255.0, 0, 255).astype(np.uint8)
normalized = image_8bit.astype(np.float32) / 255.0
normalized_16bit = np.clip(normalized_16bit, 0.0, 10.0)
# Add batch dimension and convert to tensor
tensor = torch.from_numpy(normalized_16bit.astype(np.float32)).unsqueeze(0)
return tensor
if len(normalized.shape) == 3:
tensor = torch.from_numpy(normalized).unsqueeze(0)
else:
tensor = torch.from_numpy(normalized)
return tensor.float()
class DebevecHDRProcessor:
@@ -143,13 +155,13 @@ class DebevecHDRProcessor:
if img.dtype != np.uint8:
logger.warning(f"Image {i} is not 8-bit (dtype: {img.dtype}), this may cause issues")
# CRITICAL FIX: Convert BGR to RGB for proper color handling
# OpenCV uses BGR by default, but HDR processing expects RGB
# Handle color channels properly for each algorithm
if len(img.shape) == 3 and img.shape[2] == 3: # RGB
if algorithm in ["debevec", "robertson"]:
# Only convert for algorithms that benefit from it
img_rgb = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
processed_images.append(img_rgb)
# VFX PIPELINE FIX: Test both RGB and BGR to find which works correctly
# Many Debevec color issues come from wrong channel order assumption
processed_images.append(img) # Try original first (ComfyUI tensors are typically RGB)
logger.info(f"Using original color order for {algorithm} (assuming RGB)")
else:
# For Mertens and Natural Blend, keep original format
processed_images.append(img)
@@ -180,23 +192,41 @@ class DebevecHDRProcessor:
hdr_radiance = self._blend_ev0_based(processed_images, times)
elif algorithm == "robertson":
# Robertson algorithm - alternative to Debevec
logger.info("Using Robertson algorithm...")
# Robertson algorithm - VFX pipeline style (raw linear radiance)
logger.info("Using Robertson algorithm - VFX pipeline mode...")
response = self.calibrator_robertson.process(processed_images, times)
hdr_radiance = self.merge_robertson.process(processed_images, times, response)
# Apply minimal tone mapping to preserve HDR range
hdr_radiance = self._gentle_tone_map(hdr_radiance, "Robertson")
else: # Default to Debevec
logger.info(f"Robertson raw radiance range: [{hdr_radiance.min():.6f}, {hdr_radiance.max():.6f}]")
# VFX PIPELINE: NO TONE MAPPING! Keep raw linear radiance
if hdr_radiance.max() > 1000.0: # Only if extremely bright values
scale_factor = 100.0 / np.percentile(hdr_radiance, 99.5)
hdr_radiance = hdr_radiance * scale_factor
logger.info(f"Applied minimal scaling for numerical stability: {scale_factor:.3f}")
logger.info(f"Robertson VFX output range: [{hdr_radiance.min():.6f}, {hdr_radiance.max():.6f}]")
else: # Default to Debevec - VFX pipeline style (raw linear radiance)
# Estimate camera response function using Debevec method
logger.info("Using Debevec algorithm...")
logger.info("Using Debevec algorithm - VFX pipeline mode (raw linear radiance)...")
response = self.calibrator.process(processed_images, times)
logger.info(f"Response function shape: {response.shape}")
# Merge images into HDR using Debevec algorithm
hdr_radiance = self.merge_debevec.process(processed_images, times, response)
# Apply minimal tone mapping to preserve HDR range
hdr_radiance = self._gentle_tone_map(hdr_radiance, "Debevec")
logger.info(f"Debevec raw radiance range: [{hdr_radiance.min():.6f}, {hdr_radiance.max():.6f}]")
# VFX PIPELINE: NO TONE MAPPING! Keep raw linear radiance for professional workflow
# This should look flat/log-like - that's correct for VFX
# Only apply minimal scaling if needed for numerical stability
if hdr_radiance.max() > 1000.0: # Only if extremely bright values
scale_factor = 100.0 / np.percentile(hdr_radiance, 99.5)
hdr_radiance = hdr_radiance * scale_factor
logger.info(f"Applied minimal scaling for numerical stability: {scale_factor:.3f}")
logger.info(f"Debevec VFX output range: [{hdr_radiance.min():.6f}, {hdr_radiance.max():.6f}]")
# Validate HDR output
if hdr_radiance is None or hdr_radiance.size == 0:
@@ -212,10 +242,8 @@ class DebevecHDRProcessor:
if np.all(hdr_radiance == 0):
raise ValueError("HDR merge produced all-zero result")
# CRITICAL FIX: Convert back from RGB to BGR for consistency (only if we converted earlier)
# This ensures the output color channels are in the expected order
if len(hdr_radiance.shape) == 3 and hdr_radiance.shape[2] == 3 and algorithm in ["debevec", "robertson"]:
hdr_radiance = cv2.cvtColor(hdr_radiance, cv2.COLOR_RGB2BGR)
# VFX PIPELINE: Keep output in same format as input (no additional conversions)
# ComfyUI expects consistent color order throughout the pipeline
# The result is in linear colorspace - preserve HDR data
return hdr_radiance.astype(np.float32)
@@ -631,6 +659,7 @@ class HDRExportNode:
os.makedirs(output_dir, exist_ok=True)
# Generate unique filename with timestamp
from datetime import datetime
timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
filename = f"{filename_prefix}_{timestamp}.exr"
filepath = os.path.join(output_dir, filename)