Sample a texture in HLSL

Declare and sample a texture in HLSL using a sampler.

阅读时间3 分钟

最后更新于 24 天前

To sample a texture in High-Level Shader Language (HLSL), declare a texture and its sampler. The sampler contains the properties the GPU uses to sample the texture, for example the wrap mode and filter mode. The properties usually come from the texture import settings.

注意

If your project uses the Universal Render Pipeline (URP), refer instead to Draw a texture in a shader in URP.

Follow these steps:

In the
```
HLSLPROGRAM
```
block, use the
```
UNITY_DECLARE_TEX2D
```
macro to declare the texture and its sampler. For example:
```
UNITY_DECLARE_TEX2D(_MainTex);
```
Unity creates a standard HLSL
```
Texture2D
```
object for the texture, and a standard HLSL
```
SamplerState
```
object for its sampler.

To sample the texture, use the

UNITY_SAMPLE_TEX2D

macro. For example:


half4 color = UNITY_SAMPLE_TEX2D(_MainTex, uv);

If the graphics API doesn't support separate textures and samplers, Unity does the following:

The
```
UNITY_DECLARE_TEX2D
```
macro falls back to creating a standard HLSL
```
sampler2D
```
object instead, which combines the texture and its sampler.
The
```
UNITY_SAMPLE_TEX2D_SAMPLER
```
macro samples the texture using the combined texture and sampler.

Sample other textures with the same sampler

To sample a second texture with the sampler from a texture, follow these steps:

In the

HLSLPROGRAM

block, declare the second texture using the

UNITY_DECLARE_TEX2D_NOSAMPLER

macro. For example:


UNITY_DECLARE_TEX2D_NOSAMPLER(_SecondTex);

To sample the texture, use the
```
UNITY_SAMPLE_TEX2D_SAMPLER
```
macro, passing in the first texture as the sampler source. For example:
```
half4 color = UNITY_SAMPLE_TEX2D_SAMPLER(_SecondTex, _FirstTex, uv);
```

Create a custom sampler

To create and use a custom sampler directly in a shader, also known as an inline sampler, follow these steps:

Declare a
```
SamplerState
```
object and use its name to set its properties. For example, the following code creates a custom sampler that uses point filtering and the clamp wrapping mode:
```
SamplerState my_point_clamp_sampler;
```
Sample the texture using the
```
Sample
```
method of a
```
Texture2D
```
object, and pass in the custom sampler. For example:
```
_MainTex.Sample(my_point_clamp_sampler, uv);
```

注意

Inline samplers don't work if you target the OpenGL ES or OpenGL Core graphics APIs.

For more information, refer to Built-in shader variables reference.

Example

The following example reuses the same sampler for three textures:


Shader "Custom/SeparateSamplerExample"{    Properties    {        _MainTex ("Main Texture", 2D) = "white" {}        _SecondTex ("Second Texture", 2D) = "white" {}        _ThirdTex ("Third Texture", 2D) = "white" {}    }    SubShader    {        Pass        {            HLSLPROGRAM            #pragma vertex vert            #pragma fragment frag            #include "UnityCG.cginc"            // Declare the first texture and its sampler.            UNITY_DECLARE_TEX2D(_MainTex);            // Declare the second and third textures without samplers.            UNITY_DECLARE_TEX2D_NOSAMPLER(_SecondTex);            UNITY_DECLARE_TEX2D_NOSAMPLER(_ThirdTex);            struct v2f {                float4 pos : SV_POSITION;                float2 uv : TEXCOORD0;            };            v2f vert (appdata_base v)            {                v2f o;                o.pos = UnityObjectToClipPos(v.vertex);                o.uv = v.texcoord;                return o;            }            half4 frag (v2f i) : SV_Target            {                // Sample the first texture using its own sampler.                half4 color1 = UNITY_SAMPLE_TEX2D(_MainTex, i.uv);                // Sample the second and third textures using the sampler from the first texture.                half4 color2 = UNITY_SAMPLE_TEX2D_SAMPLER(_SecondTex, _MainTex, i.uv);                half4 color3 = UNITY_SAMPLE_TEX2D_SAMPLER(_ThirdTex, _MainTex, i.uv);                // Return the combined color from all three textures.                return (color1 + color2 + color3) / 3.0;            }            ENDHLSL        }    }}

Additional resources

Use built-in shader functions
HLSL documentation on the Microsoft website

文档

Development

User Acquisition

Monetization

工业

Unity Engine

User Manual

Script Reference