Shader aliasing

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 08/01/2004 at 18:53, xxxxxxxx wrote:

User Information:
Cinema 4D Version:   6.303 
Platform:   Windows  ;   
Language(s) :   C.O.F.F.E.E  ;

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I am learning about anti-aliasing in COFFEE via the Texturing and Modelling book and sample RenderMan shader.
I often see a reference to the following:
/* Estimate the filter width -- i.e. the change from pixel to pixel -- of
* float and point values.
*/
#define filterwidth(x)  (abs(Du(x)*du) + abs(Dv(x)*dv))

How can we obtain the filterwidth for the pixel currently being shaded from the VolumeData object?
Cheers

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 09/01/2004 at 13:35, xxxxxxxx wrote:

Hard to tell without knowing what 'Du(x)' and 'du' are in the code. I don't know anything about RenderMan. Does anyone else know?

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 09/01/2004 at 15:16, xxxxxxxx wrote:

du [scalar] - Change in u across element
du [scalar] - Change in v across element
dPdu [vector] - Change in position with u
dPdv [vector] - Change in position with v
Du(expr) - Compute the parametric derivative of the expression "expr" with respect to the u parameters of the underlying surface
Dv(expr) - Compute the parametric derivative of the expression "expr" with respect to the v parameters of the underlying surface

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 10/01/2004 at 00:40, xxxxxxxx wrote:

I'm not sure what to map that to in the C4D SDK. Perhaps VolumeData::delta could do, if all you want is to avoid aliasing?