Operation flow of color difference adjustment of real three-dimensional model

The color difference of 3D model is mainly caused by the color difference of the original photo. For example, flying in the field (time, season, weather) and camera parameter setting (photo tone, definition, etc.). ) will cause the image color difference of each flight to be inconsistent. In order to eliminate the color difference of the model, we need to color the original photo or model. This scheme takes adjusting the original photo as an example to introduce the steps of image color matching, modeling engineering setting and model updating to introduce the model color matching process.

Second, the color scheme.

① Clear color matching requirements: Clear the objectives and requirements of color matching, unify the light and shadow tones, and the photo quality will be better.

② Identify the problems in the photos: high exposure, high gray scale and high noise.

③ Clear color matching steps: first, clear the initial color of the main variant, compare it with the original variant → fine-tune → copy, and apply it to all variants in a unified way.

④ Import data and process it.

Third, the choice of color matching software

Color matching recommendation CaptureOne. Because Photoshop can only use the fixed value of the main variable for batch processing, Photoshop is not selected. Even if you can see the effect, you can't unify the tone of the whole photo, and you can only batch process the photos in the folder with the same tone. However, in CaptureOne, the tone parameters of different main variants can be copied for multiple and batch tone processing, and the effect can be seen in real time, so that the overall tone of the photo is unified.

Fourth, the photo color matching process

The concrete operation process of verb (verb abbreviation) color matching

We can see that the photo below is too dark, gray, foggy and noisy. Next, the photos will be colored by Capture One software to make the overall tone consistent.

(1) Open the software, select the photo folder path, and import all the original images.

(2) In the operation bar on the right, you can see that the color and tone of the photo are not uniform. Select the exposure option menu, and adjust the exposure, high dynamic range, sharpness and defogging block to make the photo tone consistent.

Exposure: ① Exposure: the brightness of the whole picture ② Contrast: enhancing the contrast between light and dark.

③ Brightness: light and shade adjustment with small intensity ④ Saturation: enhancing chroma.

High dynamic range: mainly use the function of "shadow" to adjust the brightness of the shadow area in the photo by sliding.

Clarity: Make the whole picture clearer.

Demisting: it consists of two parts: quantity and shadow tone. Make the picture transparent, optimize the contrast and improve the black and white field.

Quantity: Click the sliding amount to adjust to the right, and the exposure, contrast and color of the whole photo will change during the adjustment process.

Shadow Tone: There are automatic and manual options. Click the eyedropper tool to manually select the shade. Click on different areas in the picture, and the color of the picture will also change. In the process of color matching, you need to click on the dark gray area in the picture instead of the dead black area, which will better interpret the color of the picture and make the color of the picture more accurate.

(3) Select the photos to be tinted and make corresponding adjustments in the menu on the left. The specific operation is as follows:

? It can be seen that the fog in this part of the photo leads to the problem of gray and low contrast. In this case, you can use exposure, high dynamic range and other tools to complete the "defogging" operation of the photo, so that the photo can achieve the best effect.

Select "Copy Adjustment Items from Main Variant" for the toned photos, and select "Apply Adjustment Items to All Selected Variants" for photos with similar colors, and perform batch operations.

After the whole photo is adjusted to one tone, export all variants, and select all (Ctrl+A)- right click-export variants.

Select the export location, export format and image quality to export all photos.

Six, the model update process

The model updating process includes two modes. One is to rebuild the model after replacing the path based on color photos. This method is equivalent to restarting 3D reconstruction, which will take a lot of time. Secondly, the intermediate result of the first modeling is used in the modeling software based on the toned photos, and only the intermediate result needs to be texture mapped again. This step method can save a lot of time. The following describes the processing flow of the second method under the bird's eye view Smart3D software.

(1) In the original project, the photos with adjusted colors were replaced. Change the photo path (color-adjusted photo) under the project. Or put the toned photos into the original project photo directory, and use the software photo path checking tool to check whether the photos have been replaced successfully.

(2) Delete the IP folder (storing the image pyramid file) under the intermediate directory in the project folder.

(3) In the reconstruction task folder corresponding to the reconstruction folder in the middle directory, select the files with textures in the block and delete them in batches.

(4) Re-submit the updated model mapping file.

? Under the reconstruction task directory, right-click to convert the data format, select the tile and format to be reconstructed, and then call up the model.

Seven. Comparison of color matching results