Similar to regular 2D textures (Texture2D class, sampler2D in shaders), cube maps (Cubemap class, samplerCUBE in shaders), and 3D textures (Texture3D class, sampler3D in shaders), Unity also supports 2D texture arrays.
A texture array is a collection of same size/format/flags 2D textures that look like a single object to the GPU, and can be sampled in the shader with a texture element index. They are useful for implementing custom terrain rendering systems or other special effects where you need an efficient way of accessing many textures of the same size and format. Elements of a 2D texture array are also known as slices, or layers.
Texture arrays need to be supported by the underlying graphics API and the GPU. They are available on:
Other platforms do not support texture arrays (OpenGL ES 2.0 or WebGL 1.0). Use SystemInfo.supports2DArrayTextures to determine texture array support at runtime.
As there is no texture import pipeline for texture arrays, they must be created from within your scripts. Use the Texture2DArray class to create and manipulate them. Note that texture arrays can be serialized as assets, so it is possible to create and fill them with data from editor scripts.
Normally, texture arrays are used purely within GPU memory, but you can use Graphics.CopyTexture, Texture2DArray.GetPixels and Texture2DArray.SetPixels to transfer pixels to and from system memory.
Texture array elements may also be used as render targets. Use RenderTexture.dimension to specify in advance whether the render target is to be a 2D texture array. The depthSlice argument to Graphics.SetRenderTarget specifies which mipmap level or cube map face to render to. On platforms that support “layered rendering” (i.e. geometry shaders), you can set the depthSlice argument to –1 to set the whole texture array as a render target. You can also use a geometry shader to render into individual elements.
Since texture arrays do not work on all platforms, shaders need to use an appropriate compilation target or feature requirement to access them. The minimum shader model compilation target that supports texture arrays is 3.5, and the feature name is 2darray.
Use these macros to declare and sample texture arrays:
The following shader example samples a texture array using object space vertex positions as coordinates:
Shader "Example/Sample2DArrayTexture"
{
Properties
{
_MyArr ("Tex", 2DArray) = "" {}
_SliceRange ("Slices", Range(0,16)) = 6
_UVScale ("UVScale", Float) = 1.0
}
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 = mul(UNITY_MATRIX_MVP, vertex);
o.uv.xy = (vertex.xy + 0.5) * _UVScale;
o.uv.z = (vertex.z + 0.5) * _SliceRange;
return o;
}
UNITY_DECLARE_TEX2DARRAY(_MyArr);
half4 frag (v2f i) : SV_Target
{
return UNITY_SAMPLE_TEX2DARRAY(_MyArr, i.uv);
}
ENDCG
}
}
}