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This article mainly introduces what is the use of watercolor wind rendering in unity3d. It has certain reference value. Interested friends can refer to it. I hope you will have a lot of gains after reading this article. Let Xiaobian take you to understand it together.

The research on watercolor wind rendering can be divided into three categories: stroke space-based methods, image space-based methods and object space-based methods.

This article proposes a pipeline for watercolor wind rendering, which belongs to the image-space-based category, as shown below.

Watercolor Wind Rendering Pipeline

Watercolor Wind Rendering Pipeline

The input to this pipeline can be a 2d image or a 3d model or a combination of both, and after abstraction and watercolor effects, the final output is a watercolor wind scene.

As shown in the figure below,(a),(b) and (c) are rendered through this pipeline. The input of (a) and (b) is a 3d model, and the input of (c) is a 2d image. After this pipeline, the final effect image is obtained.

The two components of the pipeline are described in detail below.

Abstraction (Abstraction)

Watercolor wind rendering does not require as much detail as photorealistic rendering. So, the first step in the watercolor wind rendering pipeline is to abstract or simplify the input model or image. The methods used are as follows:

Abstract lighting effect of 3d model: the expression of lighting effect in watercolor painting is generally based on the superposition of pigments. For example, wet-on-wet (wetting paper with water and then smudging it with color) generally produces a smooth overlay; wet-on-dry (drying one layer of color and then adding another, or rubbing it with a dry brush) generally produces a well-defined overlay. As shown below, picture link.

In order to achieve the above effect, you can use a toon shader to prepare a color scale map for the effect of dry painting; smooth the color scale map for the effect of wet painting smoothing, as shown below.

Even so, the model itself still has a lot of detail. So for the model itself, normal smoothing is used to simplify the details of the model. As shown below.

Abstract the color of 2d image: for 2d image, it also needs to be abstracted, and the abstract way is to adopt the method of color segmentation. Specifically, a mean shift algorithm may be employed. As shown below,(a) is the original image,(b) is the watercolor coloring effect without color segmentation, and (c) is the watercolor coloring effect with color segmentation.

Morphological Smoothing: After the previous processing, whether it is a 3D model or a 2D image, there are still some small patches, making the overall effect still look "too detailed." We can then perform a morphological smoothing filter. (d) in the above figure is the result of a morphological smoothing filter based on (c). In contrast,(d) lacks some detail.

Watercolor effects added

After the above series of abstractions, the input to the watercolor effect addition process is a 2d image. Watercolor effects are mainly divided into three parts: watercolor paper simulation, edge darkening and paint density change.

Watercolor paper is not ordinary paper, but also a lot of attention. According to texture, it is divided into coarse grain, medium coarse grain and fine grain; according to material, it is divided into wood pulp, cotton pulp and cotton wood mixture. According to the content of the painting and want to express the effect, different watercolor paper selection. For example, coarse grain is suitable for rough landscape painting, medium and coarse grain is suitable for painting still life, characters, etc., fine grain is suitable for more detailed realistic style painting.

To simulate watercolor paper, two methods are used: dry brush effects and wobbing edges. Figure (a) below shows the result without the dry brush effect and edge wiggle. Dry brush effect means that when a dry brush is drawn on a rough paper at a certain angle, the handwriting will only appear in the relatively high places of the paper, and irregular white cracks and edges will appear in the lower places, as shown in (b) below. Edge swing refers to the phenomenon that the edge of the object in the watercolor painting will swing due to the paper granularity, as shown in the figure below (c). Dry brush effects can be done with a mask, and edge wiggling can be done with an offset in the x and y coordinates of screen space.

Next, simulate the edge darkening effect, which refers to the edge darkening when the brush with higher humidity acts on dry paper. This is because the paint edge will move from the inside of the pen area to the edge in the process of drying, thus forming the edge darkening effect unique to watercolor. It is a bit like the feeling of stroke in cartoon rendering, as shown below. This effect can be achieved by convolution.

Finally, effects such as turbulence, pigment dispersion, and paper variation can be achieved through pigment density variations. As shown in the figure below, the above three effects correspond to each other, and are realized by three textures respectively.

Thank you for reading this article carefully. I hope that Xiaobian's shared article "What is the use of watercolor wind rendering in unity3d" will be helpful to everyone. At the same time, I hope that everyone will support it more, pay attention to the industry information channel, and more relevant knowledge is waiting for you to learn!

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