SampleCmp (DirectX HLSL Texture Object)
Samples a texture and compares a single component against the specified comparison value.
The comparison is a single component comparison between the first component stored in the texture, and the comparison value passed into the method.
This method can be invoked only from a pixel shader; it is not supported in a vertex or geometry shader.
Any texture-object type (except Texture2DMS, Texture2DMSArray, or Texture3D).
[in] A sampler-comparison state, which is the sampler state plus a comparison state (a comparison function and a comparison filter). See the sampler type for details and an example.
[in] The texture coordinates. The argument type is dependent on the texture-object type.
Texture-Object Type Parameter Type Texture1D float Texture1DArray, Texture2D float2 Texture2DArray¹, TextureCube float3 TextureCubeArray¹ float4
A floating-point value to use as a comparison value.
[in] An optional texture coordinate offset, which can be used for any texture-object types. The offset is applied to the location before sampling. The argument type is dependent on the texture-object type. For more info, see Applying Integer Offsets.
Texture-Object Type Parameter Type Texture1D, Texture1DArray int Texture2D, Texture2DArray¹ int2 TextureCube, TextureCubeArray¹ int3
Returns a floating point value in the range [0..1].
For each texel fetched (based on the sampler configuration of the filter mode), SampleCmp performs a comparison of the z value (3rd component of input) from the shader against the texel value (1 if the comparison passes; otherwise 0). SampleCmp then blends these 0 and 1 results for each texel together as in normal texture filtering (not an average) and returns the resulting [0..1] value to the shader.
Comparison filtering provides a basic filtering operation that is useful for percentage-closer-depth filtering.
When using this method on a floating-point resource (Instead of a signed-normalized or unsigned-normalized format), the comparison value is not automatically clamped between 0.0 and 1.0. Therefore, a manual clamp of the comparison value may be necessary for common shadowing techniques.
Minimum Shader Model
This function is supported in the following shader models.
- Texture2DArray and TextureCubeArray are available in Shader Model 4.1 or higher.
- Shader Model 4.1 is available in Direct3D 10.1 or higher.
SampleCmp is also available in ps 4_0_level_9_1 and 4_0_level_9_3 when you use the techniques that are described in Implementing shadow buffers for Direct3D feature level 9.