Bump map issue

[chrisjacks21]

I have had this issue before and never got to the bottom of it...

To bring out the detail in texture maps (especially bump maps) I generally reduce the texture blur to something like 0.01. However I have noticed on cushions/tree trunks etc that a bump map effects the smoothness/transition from light to shadow across the surface. I have attached a high-res crop to illustrate the point:

- The top image has no bump map and has a smooth transition from light to shade
- The middle image has blur set to default (1.0), shading marginally better than the bottom image
- The last images has blur set to 0.01, shading is awful but the bump detail is preserved

I thought it might be to do with the shadow bias, but after testing seems not. Any one got any ideas?

Thanks

[pixela]

Can you also render with a diffuse grey material + the bump map to check if we still see the problem ?

[chrisjacks21]

Hi Pixela - tested as you suggested and does exactly the same...

Can you also render with a diffuse grey material + the bump map to check if we still see the problem ?

[Rens]

You may need to reduce the bump amount and use .01 to .1 blur.

[vlado]

What kind of light is this? VRaySun?

Best regards,
Vlado

[3DMK]

I get this same problem with tree trunks if the bump value is too high [Vray Sun] I remember a post ages ago about this issue although I can't find it. It would be nice to have this issue resolved as sometimes you really need to increase the bump quite a lot to get the desired effect on your material, although you get this sharp transition which is not correct.

Cheers
Jamie

[Deflaminis]

Or maybe use vray HDRI map with elliptical filter instead? Would that help?

[3DMK]

I just did a small test trying to replicate the issue [see attached]

Seemed to get the same results regardless of weather the map was a bump map, vray colour2Bump or a normal map. I also tested a vray light [Disc] as well as the Vray Sun & got the same results. The shadow bias also did not fix the issue.

Cheers
Jamie

[chrisjacks21]

What kind of light is this? VRaySun?

Best regards,
Vlado

Hi Vlado - it is a VRay sun (and HDRI in a dome). I have tried both types of light independently and it still does the same.

Thanks for looking into it.

[vlado]

Yes, it's somewhere on the "to do" list to look into this.

Best regards,
Vlado

[Vizioen]

I've experienced similar issues, always thinking it had to do something with my geometry. So basically bump mapping is kind of broken? Well, that is in the case of organic objects, and with bump mapping set to a very low value.

[vlado]

So basically bump mapping is kind of broken?

Not really, it works as it is supposed to. This particular case can be improved, but it is a consequence of the very definition of bump mapping.

Best regards,
Vlado

[Neilg]

I guess the bump map adds shadowy detail to the areas in light, but cant add light detail to the areas that were originally shadowed and that where this comes from?

[vlado]

I guess the bump map adds shadowy detail to the areas in light, but cant add light detail to the areas that were originally shadowed and that where this comes from?

Exactly.

Best regards,
Vlado

[pixela]

I guess the bump map adds shadowy detail to the areas in light, but cant add light detail to the areas that were originally shadowed and that where this comes from?

A nice explanation, thanks.