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belfegor

DXT5 artifacts

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I want to try DXT5 format for my normal maps to save some memory, but i have ugly artifacts showing and i was wandering is this to be expected with this compression or am i doing something wrong?

 

Saving my "normal" normal map in photoshop as DXT5:

 

photoshop.jpg

 

and used info from here to reconstruct Z, so my pixel shader looks like this:

#pragma pack_matrix(row_major)
...
#if 1 // normal bumpmap

    float3 bump = txBump.Sample(samLinear, IN.TexCoord).xyz * 2.0f - 1.0f;

#else // dxt5

    float3 bump = txBump.Sample(samLinear, IN.TexCoord).wyy * 2.0f - 1.0f;

    bump.z = sqrt(1 - saturate(dot(bump.xy, bump.xy)));

#endif



    float3x3 tangentBasis = float3x3(normalize(IN.TangentW), normalize(IN.BinormalW), normalize(IN.NormalW));

    float3 n = normalize(mul(bump.xyz, tangentBasis));
...

Output with DXT5 (notice artifacts):

dxt5.jpg

 

and with "normal" normal map (no artifacts):

normal.jpg

 

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Renormalize the normals in the shader.

 

They come out normalized when reconstructing Z from X and Y. There's no need to do any extra normalization.

 

In fact you can probably drop the normalize on the last line of that shader.

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@MJP

 


Since you appear to be using D3D10 or D3D11...

I just started with dx11 couple of days ago.

 

If i save it as 3Dc and use same code as above i got:

bahh.jpg

 

How should i properly handle 3Dc format?

Any tool you would recommend to convert my normal maps to BC5?

 

 


...your DDS loader might bload it as BC5 if you save it as 3Dc format

IDK i am using DirectXTK DirectX::CreateDDSTextureFromFile to load my textures. How can i see which format is my texture once it is loaded?

 

@Hodgman

 


Instead of using that photoshop plugin, would you be interested in writing your own tool using a library?

Not sure what you mean? Any existing tool you would recommend to convert my textures?

 

EDIT:

I tried removing swizzle and sampling 3Dc normally:

//float3 bump = txBump.Sample(samLinear, IN.TexCoord).wyy * 2.0f - 1.0f;
float3 bump = txBump.Sample(samLinear, IN.TexCoord).xyz * 2.0f - 1.0f;
bump.z = sqrt(1 - saturate(dot(bump.xy, bump.xy)));

3dc.jpg

Edited by belfegor

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With BC5 the X and Y components will be in the red and green channels of the texture, so you would need to change your shader code to use .xy instead of .wy.

There are lots of ways you can verify the format of the texture that's created: you could step into the loader code and see what it does, you could call GetDesc on the ID3D11Texture2D to see what format it's using, or you could use a tool like VS Graphics Debugger or Renderdoc to inspect the texture.

DirectXTex has functions for compressing textures, which you could incorporate into a custom tool. It also comes with the texconv sample, which is a command-line tool that you can use for compressing files and generating mips.

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Could those blocky artifacts be caused by a point sampling magnification filter on the texture? (make sure you're using a linear magnification filter)

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No, i use same sampler for all textures, it would show on uncompressed normal map also.

D3D11_SAMPLER_DESC sampDesc;
    std::memset(&sampDesc, 0, sizeof(sampDesc));
    sampDesc.Filter = D3D11_FILTER_MIN_MAG_MIP_LINEAR;
    sampDesc.AddressU = D3D11_TEXTURE_ADDRESS_WRAP;
    sampDesc.AddressV = D3D11_TEXTURE_ADDRESS_WRAP;
    sampDesc.AddressW = D3D11_TEXTURE_ADDRESS_WRAP;
    sampDesc.ComparisonFunc = D3D11_COMPARISON_NEVER;
    sampDesc.MinLOD = 0;
    sampDesc.MaxLOD = D3D11_FLOAT32_MAX;
    hr = dev->CreateSamplerState(&sampDesc, &m_sampler);

3Dc looks fine for me for now.

Edited by belfegor

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