How to assemble a cubemap from pre-generated images per mipmap level

[ziriax]

Hello,

If I understand it correctly, one uses Texassemble to combine multiple images into a DDS file, and Texconv to generate mipmap levels.

But how can we assemble a DDS when we already have custom pre-generated images for each mipmap level? It seems Texconv can only generate the mipmap levels, not copy from existing images?

In the DirectX June 2010 SDK a GUI tool for this existed, the DirectX Texture Tool (DXTEX.EXE), that allowed manually loading images into each mipmap level. We want to automate this process.

Any help is appreciated :-)

Thanks a lot, Peter

[walbourn]

It shouldn't be difficult to extend texassemble to let you provide miplevels explicitly. I didn't see the value in having it do mipmap generation when you can just do that with texconv on the resulting DDS. It is a little tricky in terms of usability for the tool (should it just resize to the target mip level size or should it fail out?), but it's certainly doable.

[ziriax]

Thanks. We tried to use your tools to generate a Prefiltered Mipmap Radiance Environment Map from separate mipmap images for each, but it seems we better use a tool that directly generates these PMREM DDS files. What tool is not yet clear. You are not planning to add such a tool? :-)

[walbourn]

For the SimplePBR12 sample, we initially used this to create the IBL cubemaps which a number of folks reference as a starting point.

[ziriax]

Thanks for the feedback. I was hoping to find a tool for the technique described in this paper from Activision, as it seems it is so fast that it can actually be done at loading-time. But the modified cubemap gen tool will certainly do for now.

[walbourn]

There are two other tools to consider:

cmft which is an open source utility. It has both a command-line and a GUI interface.

Lys is a commercial tool for generating the cubemaps, and supports writing BC6 DDS files.

[walbourn]

Another project to consider is IBLBaker,

[ziriax]

Yes, that one is adviced by the glTF PBR group.

I have a pull request ready that can generate a cubemap from the premade MIP level images, but since I don't think my code is up to your quality standards, I am not sure if I should submit it :-) It is a bit hacky, when you ask it to build a cubemap but you provide more than 6 images, it assumes you passed all MIP levels, and then disables resizing and checks if all the images have correct downscaled sizes. Maybe a flag is needed to make this explicit.

On Thu, 1 Feb 2018, 19:25 Chuck Walbourn, notifications@github.com wrote:

Another project to consider is IBLBaker https://github.com/derkreature/IBLBaker,

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[walbourn]

This seems like something that can be added to texassemble