Texture artefacts [solved]

vincent.casi

Hi,

I tried to modify the color of a cloth by adjusting the Hue of an area (with GIMP) and the render is not nice at all whereas the texture is very sharp.
Someone has an idea why ?

Gordig

Try exporting from GIMP as a PNG. Those look like compression artifacts to me.

vincent.casi

Same results in PNG (actually I used PNG but I converted to JPG to post here a smaller file)

The only way to have ok-result is to fill with solid color, so removing the fabrics texture, as you can see in the screenshot. SOLID over SOLID gives a clean render, but loosing fabrics texture... No solution to solve that such thing ?

markusmatern

When rendering with IRAY there is one setting, that could be the cause here. Texture Compression settings of Iray itself.

Open your Render Settings tab and switch to Advanced. Check the values for Texture Compression: Medium Threshold and High Threshold.

In the past I had problems with textures having red colors. Almost the same as you have. When you set both values to 4096 and your textures are smaller than this, the artefacts may disappear. If they do at least you know what causes this.

See also this post for more information. And also this thread.

vincent.casi

Thanks !
Indeed, the thresholds were set to 512 and 1024.
I found that :
texture < Medium Threshold -> no compression
Medium Threshold < texture < High Threshold -> medium compression (small artefacts)
texture > High Threshold -> max compression (big artefacts)

So I increased the thresholds to have no compression at all and now the result is perfect.

Thanks.

markusmatern

vincent.casi said:

So I increased the thresholds to have no compression at all and now the result is perfect.

Thanks.

You are welcome! Glad I could help. You may change the threads title to Texture artefacts [solved] so people know there is a known solution.