Normal map strength in CS4

PM
Posted By
Paul_Mikulecky
Mar 4, 2009
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765
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5
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There is a strength setting for bump maps under 3d Materials, but is there a way to increase the effect of a normal map in Photoshop CS4?

Cheers,
Paul
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M
Mylenium
Mar 4, 2009
Normal maps contain the direction of a surface point with the vector components encoded as RGB channels. Changing their intensity would result in wrong directions and incorrect rendering… Without specific precautions this would be of no use except to inflate the object until it looks like a ball (as you merely ramp up the length of the vector without compensating for angular deviation). More something for dedicated sculpting tools…

Mylenium
PM
Paul_Mikulecky
Mar 4, 2009
Hmm… I can understand that occuring with displacement maps, but Maya has a strength setting for it’s normal map. It simply increases the ‘depth’ – similar to bump map setting. So it’s definitely something that can be done without inflating the object.
SG
steve_guilhamet
Mar 5, 2009
In Ps, the normal map in a material is used to replace the existing normals. It describes the vector direction only and has no scaling component, thus no strength setting. The Bump map must be used to apply any scaling.

I’m wondering if Maya’s usage is just a UI implementation that gets the value from the normal map and applies it to the bump map if it’s present? Do you see anything change if there is no bump map present?

regards,
steve
PM
Paul_Mikulecky
Mar 5, 2009
Hi Steve,

Thanks for the reply. I did some further digging and the way that Maya 7.0 works is that it uses a ‘bump’ node for normal mapping (you simply specify on the node which to use ‘tangent space normals’ or ‘bump’ (later versions of Maya also have an ‘object space normal’ option).

That node also has a strength setting. If you have the ‘bump’ setting selected and modify the strength then the change occurs in the viewport (i.e. OpenGL). If you have the ‘tangent space normals’ selected and modify the strength, the change does not occur in the viewport – but does change the appearance when you do a final render. So using a normal map the following result is using a value of 1.75 for strength:

<http://www.lostpencil.com/temp/normal_1_75.jpg>

The following result is using a value of 5.00 (a bit extreme) for strength:

<http://www.lostpencil.com/temp/normal_5_00.jpg>

I can see that having the ability to tweak the ‘strength’ of the effect of the normal map would be a nice addition when rendering in Photoshop.

Also, please note that when displaying/rendering a normal map in ‘bump’ mode, it looks quite different than when using normal map mode. It looks like an actual bump map… lots of little details instead of the ‘larger’ details captured by the normal map.

Hope this makes sense.

Cheers,
Paul
M
Mylenium
Mar 5, 2009
Maya interpolates and normalizes the vectors, which kinda is the point I was trying to make (as in PS not having such a feature). In the bump mode it seems to modify the incoming Eta of the rays fired by the renderer along the projected vector instead of fully replacing it… Unfortunately my Maya knowledge is too outdated. Haven’t used it anymore ever since v5…

Mylenium

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