steps in bump bap, even at 32 bit?

V-Ray V-Ray for 3ds Max Issues
1

that should read “bump map” i dont have an issue with bread products. or a cold. cannot edit thread title.

anyway:

Ive got a smooth gradient bump map to provide a bit of curvature to a road surface. i originally did it 8 bit, but it looked crap and steppy. so i tried recreating it in 16 bit. same issue, just slightly different stepping.

so i went the whole hog and recreated it in 32 bit, saved as an hdr, and loaded with the vrayhdri loader. i still have obvious stepping?! surely a 32 bit bump map shouldnt have this issue?

-edit, ive also tried using the standard bitmap loader with the hdr file, and the results with the original jpeg, and the 32 bit hdr version are extremely similar, as if there are the same number of greyscale steps.

-and before people think i just converted the 8 bit to 32 bit and thought that would fix it, i recreated the map from scratch, taking the original hard road mask and reapplying the blurring in a 32 bit document in photoshop.

that should give me a 32 bit gradient no?

2

What resolution is your bitmap and how much of it is on screen?

If you have an 8 bit file you can have 256 steps.
If you have a 32 bit file you can have 4294967296 steps. But if your image is only 256 pixels wide then you’ll still only have 256 samples just very very precisely defined samples. If you then have the camera so that it’s filling the screen on a 4k render then every pixel of your bump map will be 16 pixels wide in frame. This can get tricky when you’re trying to do really fine bump maps. Even with a 4k texture you might have detail that is only a pixel wide. So no matter what filtering you use or how precisely you measure that one pixel wide shape, it’s ultimately going to alias and look blocky since there isn’t enough spatial detail.

Also what filtering are you using on your bitmap? If you disabled bitmap filtering it won’t interpolate the steps which will be stair steppy no matter what.

3

the map is 2500 pix across and filling approximately 3000 pix wide on the render. obviously a bit under-rezzed, but since its soft as anything i assumed it would be ok.

its definitely banding rather than individual pixels (loads of smooth concentric rings around the sides of the road, no pixel stepping visible)

filtering, ive tried both pyramidal and summed, and in vray hdri , elliptical. blur was default at 1.

in the end i hid the effect by cranking the blur up to 10. not ideal, but i have a deadline. and im still not sure why a 32bit map would seem almost identical to an 8 bit one.

4

How were you creating this map? Photoshop? Nuke? What was the technique?

Tim J

5

as per my first post:

"and before people think i just converted the 8 bit to 32 bit and thought that would fix it, i recreated the map from scratch, taking the original hard road mask and reapplying the blurring in a 32 bit document in photoshop.

that should give me a 32 bit gradient no?"

6

And as exr instead of hdr, does that make difference?

7

That’s totally the whole thing of someone sending you a jpeg or a gif of a logo, you ask for it as an eps or ai and they send you the jpeg or gif embedded in an eps or ai. rage.

8

Have you tried with filtering off on the map?

9

ok i had a few minutes to do more testing. seems hdr files are an issue.

-when i went back and retested i didnt actually have any banding with the 16 bit png. must have made a mistake somewhere in my deadline induced rush yesterday.

so conclusion:

8bit jpeg: banding

16bit png: no banding

32 bit hdr: banding like 8 bit, maybe a bit different.

32 bit exr: no banding

32 bit hdr converted to 32 bit exr and used: banding

so, dont use hdr files for bump maps..