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# VFX Scribe

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Academic year: 2022

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## Image-based modeling

- Façade

- Tour into pictures - Single view metrology - Other approaches

## Façade

• Use a sparse set of images

• Calibrated camera (intrinsic only)

• Designed specifically for modeling architecture

• Use a set of blocks to approximate architecture

• 3 steps: geometry reconstruction, texture mapping and model refinement

• 3 steps

• Geometry reconstruction (photogrammetric modeling method)

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• Texture mapping (view-dependent texrture mpping)

• Model refinement (model-based stereo)

### Idea

It’s a new approach for modeling and rendering existing architectural scenes from a sparse set of still photographs. Our modeling

approach, which combines both geometry-based and imagebased techniques, has two components.

photogrammetricmodeling method

model-based stereo algorithm,

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Step1

### Geometry reconstruction ( photogrammetric modeling method )

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The straight line can be defined by a pair of vectors <v , d> where v represents the direction of the line and d represents a point on the line

The position of the camera with respect to world coordinates is given in terms of a rotation matrix Rj and a translation vector t

m, cameras’s normal

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Step2

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Step3

### • Model refinement (model-based stereo)

利用 Epipolar geometry 來求得深度的不同，建出更細緻更具 3D 立體感覺的的 model。

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### 重建的順序以及可能發生錯誤的部分：

Stereo reconstruction pipeline - Calibrate cameras - Rectify images - Compute disparity

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- Estimate depth

What will cause errors?

- Camera calibration errors - Poor image resolution - Occlusions

- Violations of brightness constancy (specular reflections) - Large motions

- Low-contrast image regions

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## Automatic Popup

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（ ）如圖，有兩個一大一小的圓形鼓，鼓面直徑比為 3：5，現在想要把鼓面都漆上顏色，每 一平方公分需要