c# - 如何在 Unity 中创建一个可以显示由许多小图像组成的纹理的着色器

Question

所以我想做的是从一个 SQL 表中加载卫星图像并将它们包裹在一个球体周围以创建一个地球。我知道我已经加载了覆盖的图像，我只是不确定如何让我的着色器以正确的方向显示图像。

我去过 Unity 论坛并从 Unity Docs中查看了这段代码。

使用链接的着色器代码和我在论坛上收到的帮助，这是我最终得到的代码：

Properties
    {
        _MainTexArray("Tex", 2DArray) = "" {}
        _SliceRange("Slices", Range(0,32)) = 6
        _UVScale("UVScale", Float) = 1
        _COLUMNS("Columns", Range(0, 5)) = 1
        _ROWS("Rows", Range(0, 5)) = 1
        _CELLS("Cells", Range(0, 32)) = 16
    }
        SubShader
        {
            Pass
            {
                CGPROGRAM
                #pragma vertex vert
                #pragma fragment frag
                // texture arrays are not available everywhere,
                // only compile shader on platforms where they are
                #pragma require 2darray

                #include "UnityCG.cginc"

                struct v2f
                {
                    float3 uv : TEXCOORD0;
                    float4 vertex : SV_POSITION;
                };

                float _SliceRange;
                float _UVScale;

                v2f vert(float4 vertex : POSITION)
                {
                    v2f o;
                    o.vertex = UnityObjectToClipPos(vertex);
                    o.uv.xy = (vertex.xy + 0.5) * _UVScale;
                    o.uv.z = (vertex.z + 0.5) * _SliceRange;
                    return o;
                }
                float _COLUMNS; //Columns and rows only go between 0 and 1
                float _ROWS;
                float _CELLS;
                UNITY_DECLARE_TEX2DARRAY(_MainTexArray);        
                half4 frag(v2f i) : SV_Target
                {
                    float3 uv = float3(i.uv.x * _CELLS, i.uv.y * _CELLS, 0);
                    uv.z = floor(i.uv.x / _COLUMNS) * floor(i.uv.y / _ROWS);
                    return UNITY_SAMPLE_TEX2DARRAY(_MainTexArray, uv / _CELLS); 
                }
                ENDCG
            }
        }

使用它，我的材料看起来像这样：

这是我用来加载 SQL 图像的代码：

textures = new Texture2D[size];
            for (int x = 0; x <= 7; x++) 
            {
                for (int y = 0; y <= 3; y++)
                {
                    textures[count] = tiler.Read(x, y, 2); //The z determines the zoom level, so I wouldn't want them all loaded at once
                    if (textures[count] != null) TextureScale.Bilinear(textures[count], 256, 256);
                    count++;
                }
            }


        texArr = new Texture2DArray(256, 256, textures.Length, TextureFormat.RGBA32, true, true);
        texArr.filterMode = FilterMode.Bilinear;
        texArr.wrapMode = TextureWrapMode.Repeat;
        for (int i = 0; i < textures.Length; i++)
        {
            if (textures[i] == null) continue;
            texArr.SetPixels(textures[i].GetPixels(0), i, 0);
        }    
        texArr.Apply();
        mat.SetTexture("_MainTexArray", texArr);

在 SQL 表中，x 和 y 确定图块的位置，z 确定缩放级别。我现在只使用一个缩放级别。

很抱歉链接整个着色器类，但我对着色器不是很有经验，所以我不太清楚问题出在哪里。

score 2 · Accepted Answer

如果您可以对照片数组进行索引，从而有效地获得地球的等角投影，您可以尝试使用Farfarer 从 Unity 论坛复制并稍作修改的着色器代码的修改形式：

Shader "Custom/Equirectangular" {
    Properties{
        _MainTexArray("Tex", 2DArray) = "" {}
        _COLUMNS("Columns", Int) = 2
        _ROWS("Rows", Int) = 2
    }

        SubShader{
            Pass {
                Tags {"LightMode" = "Always"}

                CGPROGRAM
                    #pragma vertex vert
                    #pragma fragment frag
                    #pragma require 2darray

                    #include "UnityCG.cginc"

                    struct appdata {
                       float4 vertex : POSITION;
                       float3 normal : NORMAL;
                    };

                    struct v2f
                    {
                        float4    pos : SV_POSITION;
                        float3    normal : TEXCOORD0;
                    };

                    v2f vert(appdata v)
                    {
                        v2f o;
                        o.pos = UnityObjectToClipPos(v.vertex);
                        o.normal = v.normal;
                        return o;
                    }

                    UNITY_DECLARE_TEX2DARRAY(_MainTexArray);

                    int _ROWS;
                    int _COLUMNS;

                    #define PI 3.141592653589793

                    inline float2 RadialCoords(float3 a_coords)
                    {
                        float3 a_coords_n = normalize(a_coords);
                        float lon = atan2(a_coords_n.z, a_coords_n.x);
                        float lat = acos(a_coords_n.y);
                        float2 sphereCoords = float2(lon, lat) * (1.0 / PI);
                        return float2(sphereCoords.x * 0.5 + 0.5, 1 - sphereCoords.y);
                    }

                    float4 frag(v2f IN) : COLOR
                    {
                        float2 equiUV = RadialCoords(IN.normal);

                        float2 texIndex;
                        float2 uvInTex = modf(equiUV * float2(_COLUMNS,_ROWS), texIndex);

                        int flatTexIndex = texIndex.x * _ROWS + texIndex.y;

                        return UNITY_SAMPLE_TEX2DARRAY(_MainTexArray,
                                float3(uvInTex, flatTexIndex));
                    }
                ENDCG
            }
        }
    FallBack "VertexLit"
}

你还需要使用

texArr = new Texture2DArray(256, 256, textures.Length, TextureFormat.RGBA32, false, true);

代替

texArr = new Texture2DArray(256, 256, textures.Length, TextureFormat.RGBA32, true, false);

如果我将此脚本附加到球体，它对我有用：

Material myMat;
public List<Texture2D> texes;

IEnumerator Start()
{
    yield return null;
    myMat = GetComponent<Renderer>().material;

    Texture2DArray texArr = new Texture2DArray(256, 256, 9, 
            TextureFormat.RGBA32, false, true);
    texArr.filterMode = FilterMode.Bilinear;
    texArr.wrapMode = TextureWrapMode.Clamp;

    for (int i = 0 ; i < texes.Count ; i++)
    {
        texArr.SetPixels(texes[i].GetPixels(), i, 0);
    }

    texArr.Apply();

    myMat.SetTexture("_MainTexArray", texArr);
}

并按texes顺序添加这些纹理：

0：