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some basic concepts?
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I realize not everyone on this board speaks english as first language. But it will not help your chance of getting a reply if your question makes very little sense...
That said I *think* the issue you are trying grapple with is the "homogenous coordinates". The short answer is a that the W (fourth) component of a vector is always 0 for direction vector and always 1 for a position. For more information google "homogenous coordinates" (the wiki page has a section on grahics at the end http://en.wikipedia.org/wiki/Homogeneous_coordinates#Use%20in%20computer%20graphics)
Lighting calculations require a camera direction as the appearance of material depends on the view it is being look from, simple "N dot L" lighting models ignore this but more complex models (usually those invovling a specular component) will take this into account, so need the camera direction.
That said I *think* the issue you are trying grapple with is the "homogenous coordinates". The short answer is a that the W (fourth) component of a vector is always 0 for direction vector and always 1 for a position. For more information google "homogenous coordinates" (the wiki page has a section on grahics at the end http://en.wikipedia.org/wiki/Homogeneous_coordinates#Use%20in%20computer%20graphics)
Lighting calculations require a camera direction as the appearance of material depends on the view it is being look from, simple "N dot L" lighting models ignore this but more complex models (usually those invovling a specular component) will take this into account, so need the camera direction.
If you'd like to find out more on your third query, you may want to Google 'perspective-correct lighting'. The specular lighting model is the simplest and most common of such.
Regards
Admiral
Regards
Admiral
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