[Bf-committers] cloud/marble/wood bump patch

[Matt Ebb]

On 11 Jan 2004, at 10:27 AM, Alexander Ewering wrote:
> On Sat, 10 Jan 2004, car wrote:
>
>> All of this. Is it the method to create Normal mapping ? Or something
>> close ?
>> All I know of is that bump mapping does it's thing in the z axis, so  
>> at
>> the corners of the mesh the bump detail falls off and loses it's  
>> charm.
>> While Normal mapping does it's thing on all axis's x,y,z,

---snip---

>> I had thought that during the displacement render that the displaced
>> mesh could then have it's detail extracted and made into a normal map.
>> So then whatever Ton and eeshlo are doing here could be used for the
>> extra fine details into blender.
>>
>> Or would Blenders renderer need a re-justment ?
>
> trig_dragon, you have a very flawed understanding of bump mapping.
>
> It is of no importance in whatever way you change the normals of the
> faces during render, you will never get detail at the "corners" of a  
> mesh,
> because there _is_ no detail.
>
> What do you mean by "does its thing in the Z Axis"? What Z Axis?  
> Texture
> mapping never modifies the actual mesh data, so it doesn't make sense  
> to
> talk about axes at all. All that is done is rotating normal vectors  
> using
> intensity levels, which merely modifies the _shading_ of the rendered  
> faces,
> never the geometry.

He's talking about the technique of extracting detail from a  
high-resolution surface and converting it to a displacement map or an  
RGB normal map. Using an RGB normal map apparently looks more accurate,  
particularly along the edges of a model, as it doesn't just control how  
much to shift the normal when shading, it controls the vector that it  
is shifted along. This has been done quite frequently recently and has  
been popularised by Zbrush (and is IIRC how they did a lot of the  
character modelling on Lord of the Rings).

Here are a few links with better descriptions of this technique:

http://www.cgtalk.com/showthread.php?s=&threadid=79121&pagenumber=5
http://www.brilliant-creations.com/amapidemontut.htm
http://www.drone.org/tutorials/displacement_maps.html
http://www.pixolator.com/zbc-bin/ultimatebb.cgi? 
ubb=get_topic&f=1&t=012018
http://cube.phlatt.net/forums/spiraloid/viewtopic.php?TopicID=9&page=2
http://amber.rc.arizona.edu/lw/normalmaps.html

Matt