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DXT5 artifacts


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#1 belfegor   Crossbones+   -  Reputation: 2788

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Posted 26 June 2014 - 02:59 PM

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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#2 L. Spiro   Crossbones+   -  Reputation: 20127

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Posted 26 June 2014 - 03:31 PM

Renormalize the normals in the shader.


L. Spiro

#3 MJP   Moderators   -  Reputation: 14016

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Posted 26 June 2014 - 04:51 PM

Since you appear to be using D3D10 or D3D11, you should consider switching to BC5. It will give better quality than using the green and alpha channels of DXT5. That Nvidia plugin is from before D3D10 so it doesn't have BC5, but it's functionally equivalent to the 3Dc format so your DDS loader might bload it as BC5 if you save it as 3Dc format.



#4 Adam_42   Crossbones+   -  Reputation: 2814

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Posted 26 June 2014 - 04:58 PM


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.



#5 Hodgman   Moderators   -  Reputation: 40029

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Posted 26 June 2014 - 05:40 PM

All the BC/DXT formats will have some artifacts. Yours looks pretty good except for the blocky/squares down the bottom of the picture... There's many ways to create DXT/BC files though, each will take different amounts of time and produce different levels of quality. Instead of using that photoshop plugin, would you be interested in writing your own tool using a library?



#6 belfegor   Crossbones+   -  Reputation: 2788

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Posted 26 June 2014 - 06:17 PM

@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, 26 June 2014 - 06:36 PM.


#7 MJP   Moderators   -  Reputation: 14016

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Posted 26 June 2014 - 06:37 PM

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.



#8 belfegor   Crossbones+   -  Reputation: 2788

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Posted 26 June 2014 - 06:50 PM

It is BC5 as you said:

bc5.jpg

 

This wiki page says that 3dc & bc5 are the same



#9 C0lumbo   Crossbones+   -  Reputation: 2997

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Posted 27 June 2014 - 01:23 AM

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



#10 belfegor   Crossbones+   -  Reputation: 2788

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Posted 27 June 2014 - 02:26 AM

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, 27 June 2014 - 02:28 AM.


#11 Alessio1989   Members   -  Reputation: 2810

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Posted 27 June 2014 - 06:31 AM

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



Texconv from DirectXTex: https://directxtex.codeplex.com/

 

It support GPGPU (via CS) acceleration.


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