Bump map aspect ratio dramatic influence!?!?

[RSF]

Hello.
This is a very annoying issue.
Bump map aspect ratio dramatically changes its effect.
I was mapping a curb and was using a very thin bum map when I noticed this.
Here are 2 renders using the same base image although one is a square repetition of the other.
I also included max scene with the textures.

I didn't knew this "always use square bump maps" law...
I'm I missing something here??

[RSF]

it seams like it's not so much the aspect ratio but the length in each component of the map.

Even though the rendered resolution is the same repeating e tiny bump map gives a more faded effect than if you just make a bigger map that is only a repetition of the same texture.

Anyone having the same results?

[vlado]

Do you have the scene?

Best regards,
Vlado

[RSF]

yes...sorry forgot to post it...ups...no I didn't....it was to large and was blocked...161BK is to large!??!

Well...here it goes 1 file at the time...

[RSF]

Any updates on this issue?
Thanks

[vlado]

Well, it seems to be "as designed" since both the scanline renderer and mental ray render it the same way too. I guess the issue is that internally, all bitmaps are stretched to the unit square.

Best regards,
Vlado

[RSF]

Ok...I'll make only square bumps from now on...
Thanks Vlado

[tammo]

I didn't know about that.
Thanks for posting.

Reminds me of game engines,
they also use only square maps.

[voltron7]

Good find, and thanks for posting about this. Always wondered about that...

[bardo]

but if vlado said "..all bitmaps are stretched to the unit square" it means that not only bump is affected ... probably to avoid problems it's better to use square bitmap aspect ratio also for diffuse and the others parameters.

I need to do some tests.