Alain <kua### [at] videotronca> wrote:

> > Warp <war### [at] tagpovrayorg> wrote:
> >> CAS <sup### [at] cstnetcn> wrote:
> >>> 1: how does pov calculate the value of each pixel of final image?
> >>
> >> Via raytracing. Mathematical rays are "shot" from the "camera" towards
> >> the (mathematically defined) scene geometry, and intersections between
> >> this ray and the surfaces are calculated. Then the normal vector and
> >> texture of the surface at that point are calculated, and its color from
> >> them.
> >>
> >>> My
> >>> understanding is :using the irradiance and surface properties to calculate the
> >>> value of each pixel of final image. Using the simplistic Phong lighting model to
> >>> calculate the color of each pixel of final image.I didnot set related "phong"
> >>> statements but also get a result.
> >>
> >> The "phong lighting model" has nothing to do with "phong highlights".
> >> The latter is one algorithm to calculate (simplistic) highlights, and
> >> you can use it, or another, or none at all.
> >>
> >> The "phong lighting model" means that the color of the surface at a given
> >> point is calculated by taking the texture color at that point, adding a
> >> possible (fixed) ambient color to it, multiplying it with a diffuse
> >> component (which is calculated from the direction and intensity of light
> >> sources), and adding a specular component to it (which is calculated
> >> similarly, but with a different algorithm that also takes into account
> >> the direction of the incoming ray.)
> >>
> >> POV-Ray also supports a few alternative lighting models that can be
> >> added to that.
> >>
> >> --
> >>                                                            - Warp
> >
> > Thank you for your help.I am sorry to trouble you again! I want to use phong or
> > radiosity (such illumination model) to calculate,how can I set relation
> > statements? I have defined some paraments in global_settings {phong{}} but when
> > pov is running ,it points out "phong 0".What values are these specific
> > parameters should I set?
> >
> >
> >
>
> The phong lighting model is the DEFAULT and ONLY model and can't be
> changed. It CAN'T be used in the global_settings section.
>
> The phong key word is used to produce highlights that use the phong
> model. It belong in the finish block of your textures. it's used as follow:
> finish{phong Phong_Intensity phong_size Value}
>
> Alternatively, or at the same time, you can use specular to produce
> highlights. It's to be used as follow:
> finish{specular Specular_Intensity roughness Value}
>
> Both result in similar, but slightly different, highlights.
>
> radiosity is a global seting feature that enable diffuse
> inter-reflection between the objects in your scene. It's purpose is to
> replace the ambient part of your finish. In version 3.7, enabling
> radiosity will disable the ambient component of all finishes. When using
> radiosity, if you want some glowing objects, you now add:
> finish{emission Value}
>
>
>
> Alain

I want to simulate the reflectance image or radiance image. My step is:
1,construct geometric model
2,render geometric model
Then I have defined  solar irradiance,  sun position, camera position,  real
location of each object and real material properties of each object, then  pov
use phong illumination model to calculate the light intensity of each object
(phong model can get the physical significance of the results?) , I have saved
the results in a HDR image,all is OK. But the result is not what I wanted ,the
value is smaller than what I need. I am so confusing.

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