Incorrect Texture

Greetings!
Thanks CodeImp for your great program.

I create my own textures and some of them become incorrect when i start testing map. On a picture you can see, that texture on wall is displacing. It's almost fine. But look at the floor! What is this? How do I fix it?
Where is my fault (or is it MY fault?)

I doubt this is DB's doing. Probably you have your flat lump in an incorrect format (it looks like the texture is being read as a different format), not sure though. I'll move this topic to the editing forum, I'm sure someone can recognize the problem. Perhaps you can tell us what sourceport you use and how did you import your texture and/or flat into your wad?

Ok. I use XWE (extendable wad editor) to add new textures (in *.bmp format) in my wad.
Options in DoomBuilder: IWAD - Doom2.wad, Additional wad - mywad.wad, format: Zdoom (doom in hexen format), Port - Zdoom.
All looks great in 3dmode, but when i start testing... see the shot.
I think that:
1. maybe this is XWE error and I should use another WAD editor
2. this error occure after map compile

That map doesn't "compile" to the extent that something like that would happen between the time you edit it and the time you save/test it.

I am not the ZDoom expert, but the way the texture has been smashed down in size, it looks like you're trying to load a flat larger than 64x64. ZDoom supports using large textures/patches on flats, but certain WAD construction tools will automatically resize anything loaded as a flat to a resolution of 64x64, and if your original image is, say, 128x256, you'll get a 50% downsize on the vertical and a 75% downsize on the horizontal when loading it as a flat, which would explain why your flat looks like its made of rectangular tiles instead of square tiles.

But then, as far as I know, ZDoom has been able to use regular wall textures and other patches as flats (and vice versa) for quite a few versions, so you shouldn't even need to double-load it as both a wall texture and flat if that's what you're doing.

an original image has 48x48 size (two black & two white squares) and it's wall texture (not flat).

Gotcha!
The problem is in texture' resolution. Lüt, you were close to answer. Texture must be 64x64 or higher. Otherwise you'll get the same thing as I.

Thanx all, who triyng to help!