Sharpness map innacurate because of transition to stb_image.

[Gyrth]

I've noticed while running the internal_testing branch on Steam that thrown weapons no longer stick to characters. I compared building after and before commit d4aa66b. And here it seems the issue was introduced. However I can not seem to solve it. I know it has something to do with caching the images to the disk. I thought that compression was causing the sharpness maps to get blurry and that made the sharpness values to be lower than absolute white. This is what I tried so far.

• Setting stbi_write_png_compression_level to 0
• Setting stbi_write_png_compression_level to 10
• Changing the stbi_write_png comp value to 4 in image_export.cpp

Now the last attempt at a fix did not solve the sharpness issue, but it did fix the terrain normal map generation. Here is what it looks like before and after. By using the comp value 3 (RGB) it generated a lot of vertical lines, but adding 4 (RGBA) this no longer happens. Maybe you can shed some light on this @feliwir?

[feliwir]

@Gyrth setting/changing the compression level should make no difference, since PNG is a lossless format. It just sets the internal deflate compression level.
You're right that the amount of components seems to be wrong here:
d4aa66b#diff-ff31ad9a5068f6649cb3d495abaf5447550115e00873c8ada8835f85dcc5fd51R121
and
d4aa66b#diff-ff31ad9a5068f6649cb3d495abaf5447550115e00873c8ada8835f85dcc5fd51R125
This should be 4 (RGBA = 4 components).

Regarding the issue with the sharpness map:
If i had to guess i'd say the problem is in image_sampler.cpp, but i'd need to validate this.

[Gyrth]

@feliwir I don't understand why adding an Alpha fixes the colors. As far as I know, this channel isn't even used for normal maps. It just needs RGB values for an Object Space Normal Map.

[feliwir]

@Gyrth this is about memory layout. We don't add an alpha but it's already there.
the incoming data is layouted as follows for each pixel:
RGBA-RGBA-RGBA-RGBA
when we now tell stb_image that we only have 3 components, it will interpret the data as
RGB-RGB-RGB-RGB
So it will start being wrong starting from the second pixel, where it will use the A as the R and so on.

[autious]

@Gyrth did you have a local fix for this problem?

[Gyrth]

@Gyrth did you have a local fix for this problem?

For the terrain normal map issue, yes. But for the sharpness map issue with weapons I couldn't find a solution.

[autious]

Understood!