[R] wireframe shade=T colorkey

[Duncan Murdoch]

On 10/11/2007 6:32 PM, Deepayan Sarkar wrote:
> On 10/11/07, Karim Rahim <karim.rahim at gmail.com> wrote:
>> Thank you for your reply.
>>
>> In this graphics context, I'm not sure what the incident or reflected
>> light rays are.
>>
>> May I ask for an example of using a colour key with the volcano data
>> using the colours that appear when you select the shade option?
>>
>> It is simple to have the colour key appear using drape. Perhaps it is
>> not so simple to have a colour key using shade colours or different
>> colours. Once again, may I ask for an example of setting these colour
>> key and/or colour options?
> 
> I'm not really sure what you want. The goal of the colorkey is to
> associate a given z-value (or height) with a specific color.
> drape=TRUE does this, e.g.,
> 
> wireframe(volcano, drape = TRUE, colorkey = TRUE)
> 
> Now, with shade=TRUE, e.g.,
> 
> wireframe(volcano, shade = TRUE)
> 
> the SAME Z-VALUE CAN HAVE DIFFERENT COLORS depending on the
> orientation of the facet with respect to the viewing direction and the
> light source. So, a colorkey DOES NOT MAKE SENSE.

But the colorkey could display what the color would be at some 
particular orientation, with height allowed to vary, or perhaps with 
fixed values for irradiance and reflective angle.  With the standard 
palette this should be readable because the height determines the hue, 
and (non-colorblind) people are good at recognizing hue even when 
saturation and brightness vary.

Duncan Murdoch