Windows API Reference

Textures in DirectX

Textures are fundamental to modern graphics rendering. They are typically 2D or 3D arrays of texels (texture elements) that can be applied to surfaces of 3D objects to provide color, surface detail, or other visual properties. DirectX provides a robust set of APIs for creating, managing, and sampling textures.

Texture Basics

A texture in DirectX is represented by a texture object. These objects store the image data and associated metadata, such as dimensions, format, and mipmap levels. The most common types of textures include:

Texture Formats

Textures can be stored in various pixel formats, which define the number of bits per pixel and how color channels (Red, Green, Blue, Alpha) and other data are represented. Common formats include:

• DXGI_FORMAT_R8G8B8A8_UNORM: 8 bits per channel, normalized unsigned integer.
• DXGI_FORMAT_B8G8R8A8_UNORM: Similar to the above, but with channel order BGR.
• DXGI_FORMAT_BC1_UNORM: Block Compression (DXT1) format.
• DXGI_FORMAT_D32_FLOAT: 32-bit floating-point format, often used for depth buffers.

Choosing the right format is crucial for performance and memory usage. Compressed formats like BC1-BC7 offer significant space savings with minimal visual quality loss.

Mipmaps

Mipmaps are pre-calculated, downscaled versions of a texture. When rendering a textured object, the GPU can select the appropriate mipmap level based on the distance of the surface from the camera. This significantly reduces aliasing artifacts (like shimmering) and improves performance by using smaller textures when objects are far away. Mipmaps are generated either during texture creation or at runtime.

Creating and Using Textures

The process of using textures generally involves these steps:

1. Load or Generate Texture Data: This can be done by loading image files (like .dds, .png, .jpg) or by generating procedural textures.
2. Create a D3D11_TEXTURE2D_DESC (or similar) structure: This structure defines the properties of the texture, including dimensions, format, mipmap count, usage, and bind flags.
3. Create the Texture Resource: Use ID3D11Device::CreateTexture2D (or related functions) to create the texture object.
4. Create a Shader Resource View (SRV): An SRV is a view into the texture resource that allows shaders to read from it. Use ID3D11Device::CreateShaderResourceView.
5. Bind the SRV to the Pipeline: In your rendering code, set the SRV to a specific shader resource slot using ID3D11DeviceContext::PSSetShaderResources (for pixel shaders).
6. Sample in the Shader: In your HLSL shader code, declare a sampler and a texture variable, and use the Sample function to retrieve texel data.

Example Shader Code Snippet:

// In your HLSL shader
Texture2D myTexture;
SamplerState mySamplerState;

float4 PSMain(PS_INPUT input) : SV_TARGET
{
    // Sample the texture at the given UV coordinates
    float4 texColor = myTexture.Sample(mySamplerState, input.Tex);
    return texColor;
}
            

Usage and Bind Flags

When creating a texture, you specify its intended usage and how it will be bound to the graphics pipeline using bind flags. Key flags include:

• D3D11_BIND_SHADER_RESOURCE: The texture will be read from by shaders.
• D3D11_BIND_RENDER_TARGET: The texture will be rendered into (as a render target).
• D3D11_BIND_DEPTH_STENCIL: The texture will be used for depth/stencil testing.

Further Reading

• DirectXTex Library (for texture loading, processing, and conversion)
• DXGI Formats