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Horus_Sungod

Issue in RGBA Heightfield Export

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Hello,

when exporting an image from the Heightfield Output node, when the .tga image is set to RGBA, the non-alpha channels are sorta polluted by the alpha.

On the left, a direction mask, works fine, when exported into an 8 bit RGB tga.

When I put the output node to RGBA and put something like sediments in the alpha, it affects the green channel (where the direction mask is stored), and there are no values of gray left, only pure black and white. Changing which layer is put in the alpha affects how the other three channels get polluted.

Is there an option I'm missing? Is there a way to export an image in RGBA without getting unwanted results in the R, G and B channels?

Thank you

houdiniBug.jpg

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.tga by default is premultiplied by it's alpha and it has and sRGB look up to it. You best bet is to use a linear texture format such as .exr which is linear by nature and is loaded by most engines. I know Unity and Unreal do now load 16 bit of the data.

Look at these documents for more info.

https://www.sidefx.com/docs/houdini/render/linear.html

TGA is a really outdated texture format and I would highly recommend to discontinue use of it in production. 

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Hello,

I only require an 8 bit image for a splat map, a very deep 16 bits is probably overkill.

More basic software, like Substance Painter, can output a TGA without the alpha corrupting the RGB channels. I would find it strange that Houdini could not do the same? Will I need some kind of image compositing, where the Alpha is added to the RGB later on?

PNG does not have a separate alpha channel, and unreal does not support tiff files, hence why I usually use TGAs.

Would you recommend .exr for any textures in games, or simply for the specific cases such as a terrain splatmap?

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You said you were exporting heightmaps earlier. For those certainly use .exr, anything with 16 bit data scope. EXR are little large for general use everywhere, and most game engines always by default expect them to be data maps as the information is lossless pixel value for pixel value. 

I still can't believe unreal can't handle .tiff how many decades before they fix that...

As far as TGA Houdini is not necessarily exporting it wrong, and Substance is not necessarily exporting it right. Their default exports and options are designed for two different use cases. Houdini default was not intended to create textures through tga. tga has not been used in other industries besides games in a very long time. You can export out of Houdini with out doing the premult and the other effects you are seeing, but you would need to share a simple scene file. There are many workflows to export and ways the data might change so it's hard to tell you specifically what setting too change with out giving a very vague list.  

PNG should have a separate alpha channel. I would have to see your example file to explain why your having that issue.

 

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