Comparison of SamplerCmp and Sample

Oct 13, 2025 by talynt.org 9 views

Introduction

In the world of computer graphics, Shadow Mapping is a technique used to create realistic shadows in 3D scenes. One of the key components of Shadow Mapping is Point Cloud Filtering (PCF), which helps to reduce the aliasing artifacts that can occur when sampling a shadow map. In this article, we will explore how SamplerCmp works compared to Sample (PCF shadow blur) in the context of 3D graphics programming.

What is SamplerCmp?

SamplerCmp is a texture sampling function in DirectX 11 that allows for comparative sampling of a texture. This means that it can compare the sampled value with a threshold value, and return a value based on the comparison. In the context of Shadow Mapping, SamplerCmp is used to perform a PCF blur on a shadow map, which helps to reduce the aliasing artifacts that can occur when sampling the shadow map.

What is Sample?

Sample is a texture sampling function in DirectX 11 that returns the sampled value of a texture at a given location. In the context of Shadow Mapping, Sample is used to sample a shadow map, and then perform a PCF blur on the sampled value to reduce aliasing artifacts.

How Does SamplerCmp Work?

SamplerCmp works by comparing the sampled value of a texture with a threshold value. If the sampled value is greater than or equal to the threshold value, SamplerCmp returns the sampled value. Otherwise, it returns a value of 0. This allows SamplerCmp to perform a PCF blur on a shadow map, by sampling the shadow map at multiple locations and comparing the sampled values with a threshold value.

How Does Sample Work?

Sample works by simply returning the sampled value of a texture at a given location. In the context of Shadow Mapping, Sample is used to sample a shadow map, and then perform a PCF blur on the sampled value to reduce aliasing artifacts.

Comparison of SamplerCmp and Sample

In terms of performance, SamplerCmp is generally faster than Sample, since it only needs to perform a single comparison operation. However, Sample can be more flexible, since it allows for more complex sampling operations.

In terms of image quality, SamplerCmp can produce better results than Sample, since it can perform a more accurate PCF blur. However, Sample can still produce good results, especially if the shadow map is well-sampled.

Code Comparison

Here is an example of how SamplerCmp and Sample can be used to perform a PCF blur on a shadow map:

// SamplerCmp example
float4 samCmpLess(float2 uv, float threshold) : SV_Target
{
    float4 color = float4(0, 0, 0, 1);
    for (int i = -1; i <= 1; i++)
    {
        for (int j = -1; j <= 1; j++)
        {
            float2 offset = float2(i, j) / 3.0;
            float4 sample = Texture.SampleCmp(sampler, uv + offset, threshold);
            color += sample;
        }
    }
    return color / 9.0;
}
// Sample example
float4 samClamp(float2 uv) : SV_Target
{
float4 color = float4(0, 0, 0, 1);
for (int i = -1; i <= 1; i++)
{
for (int j = -1; j <= 1; j++)
{
float2 offset = float2(i, j) / 3.0;
float4 sample = Texture.Sample(sampler, uv + offset);
color += sample;
}
}
return color / 9.0;
}

In this example, SamplerCmp is used to perform a PCF blur on a shadow map, by comparing the sampled values with a threshold value. Sample is used to perform a PCF blur on a shadow map, by simply sampling the shadow map at multiple locations.

Conclusion

In conclusion, SamplerCmp and Sample are both useful texture sampling functions in DirectX 11, but they have different use cases. SamplerCmp is generally faster and more accurate than Sample, but it can be less flexible. Sample can be more flexible, but it can be slower and less accurate. Ultimately, the choice between SamplerCmp and Sample will depend on the specific requirements of the project.

Recommendations

Based on the comparison of SamplerCmp and Sample, here are some recommendations:

Use SamplerCmp when performing a PCF blur on a shadow map, since it can produce better results and is generally faster.
Use Sample when performing a PCF blur on a shadow map, but only if the shadow map is well-sampled and the PCF blur is not critical.
Use SamplerCmp when performing a PCF blur on a texture, since it can produce better results and is generally faster.
Use Sample when performing a PCF blur on a texture, but only if the texture is well-sampled and the PCF blur is not critical.

Future Work

Introduction

In our previous article, we explored the differences between SamplerCmp and Sample in the context of 3D graphics programming, specifically in the area of Shadow Mapping and Point Cloud Filtering (PCF). In this article, we will answer some frequently asked questions about SamplerCmp and Sample, and provide additional information to help you understand the differences between these two texture sampling functions.

Q: What is the main difference between SamplerCmp and Sample?

A: The main difference between SamplerCmp and Sample is that SamplerCmp performs a comparison operation on the sampled value, while Sample simply returns the sampled value. This means that SamplerCmp can be used to perform a PCF blur on a shadow map, while Sample can be used to sample a shadow map without performing a PCF blur.

Q: Which one is faster, SamplerCmp or Sample?

A: SamplerCmp is generally faster than Sample, since it only needs to perform a single comparison operation. However, Sample can be more flexible, since it allows for more complex sampling operations.

Q: Which one produces better results, SamplerCmp or Sample?

A: SamplerCmp can produce better results than Sample, since it can perform a more accurate PCF blur. However, Sample can still produce good results, especially if the shadow map is well-sampled.

Q: Can I use SamplerCmp for other purposes besides PCF blur?

A: Yes, you can use SamplerCmp for other purposes besides PCF blur. For example, you can use it to perform a PCF blur on a texture, or to compare the sampled value of a texture with a threshold value.

Q: Can I use Sample for other purposes besides sampling a shadow map?

A: Yes, you can use Sample for other purposes besides sampling a shadow map. For example, you can use it to sample a texture, or to perform a PCF blur on a texture.

Q: What are the advantages and disadvantages of using SamplerCmp?

A: The advantages of using SamplerCmp are:

It can produce better results than Sample for PCF blur operations.
It is generally faster than Sample.
It can be used for other purposes besides PCF blur, such as comparing the sampled value of a texture with a threshold value.

The disadvantages of using SamplerCmp are:

It can be less flexible than Sample, since it only performs a single comparison operation.
It may not produce good results if the shadow map is not well-sampled.

Q: What are the advantages and disadvantages of using Sample?

A: The advantages of using Sample are:

It is more flexible than SamplerCmp, since it allows for more complex sampling operations.
It can produce good results even if the shadow map is not well-sampled.

The disadvantages of using Sample are:

It may not produce as good results as SamplerCmp for PCF blur operations.
It can be slower than SamplerCmp.

Conclusion

Recommendations

Based on the comparison of SamplerCmp and Sample, here are some recommendations:

Use SamplerCmp when performing a PCF blur on a shadow map, since it can produce better results and is generally faster.
Use Sample when performing a PCF blur on a shadow map, but only if the shadow map is well-sampled and the PCF blur is not critical.
Use SamplerCmp when performing a PCF blur on a texture, since it can produce better results and is generally faster.
Use Sample when performing a PCF blur on a texture, but only if the texture is well-sampled and the PCF blur is not critical.

Future Work

In the future, it would be interesting to explore other texture sampling functions in DirectX 11, such as SamplerLinear and SamplerAnisotropic. It would also be interesting to explore other techniques for reducing aliasing artifacts in Shadow Mapping, such as Screen Space Ambient Occlusion (SSAO) and Screen Space Global Illumination (SSGI).