Unity3d learning note 9 - loading textures

1. summary

Theoretically ,Unity There is no difficulty loading textures in , Just place the picture in Assets In the folder , It will be recognized as a texture , So it can be loaded into the scene . But once there is some extra demand , You have to use other ways to load textures .

2. Detailed discussion

2.1. Resources The way

Use Resources Mechanism to load Unity Various resources , Include texture ：

Texture2D texture = Resources.Load<Texture2D>("ImageDemo");

Resources yes Unity The resource management provided by the program .Resources This mechanism is especially suitable for games , For games , All the textures 、 texture of material 、Shader Etc. can be used as the built-in resources of the game .

2.2. API The way

Consider this situation ： If the data we want to process comes from outside resources , That is, it is stored in the resource folder of the operating system . This situation Resources Can't use . In this case, we should understand the principle of texture ： Texture images are first stored in hard disk space , And then through CPU Read into memory , Finally, the data is exchanged to GPU In the video memory of .

One way is to use image processing for reference , Such as GDAL、OpenCV etc. （ You can even pass by yourself File Realization ） Components , Read the image into memory , Organized into Unity Script class Texture2d Needed buffer：

int width = 512;
int height = 512;
texture = new Texture2D(width, height, TextureFormat.RGB24, false);

byte[] imgData = new byte[width * height * 3];

for(int yi = 0; yi< 128; yi++)
{
    
    for(int xi = 0; xi < 128; xi++)
    {
    
        int m = width * 3 * yi + 3 * xi;
        imgData[m] = 135;
        imgData[m+1] = 206;
        imgData[m+2] = 235;
    }
}

texture.SetPixelData(imgData, 0, 0);
texture.Apply(false, false);

I will memory buffer front 128*128 Pixel buffer Fill in blue , It turns out to be ：

That is, texture buffer It also starts from the lower left corner .

Apply() This function cannot be less , Because this function uploads the texture data in memory to GPU In the video memory of , And it costs more performance . It is best to change the pixel value after , Just once Apply() Upload to GPU.

2.3. Web The way

Except for the local , Resources are sometimes placed on remote servers . Regarding this Unity Provides WWW Class as the access interface , But it has been abandoned . Now? Unity Provide UnityWebRequest Class as and Web Interface for server communication , And access remote Texture Related classes include UnityWebRequestTexture. This set of interfaces is briefly studied , It also seems to provide asynchronous methods .

But I didn't use this interface in actual use . Because I want to put part of my work into multithreading . We know Unity Content related to rendering or resources cannot be put into multithreading , But accessing remote data 、 And the content read into memory can be put into multithreading . So the way of improvement is also very simple ：

1. Use C# Of WebRequest Interface （ Other network transmission interfaces are also ok ）, Generally, the interface of network transmission can be placed in multithreading .
2. Parse the obtained file stream , obtain RGB Format memory Buffer. This step can also be placed in multithreading .
3. In the main thread, the memory Buffer Insert into Texture2D in .

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