Talk:Phong reflection model

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[edit] Definition of L in Phong equation

Shouldn't L be the vector from the point on the surface to the light source? All other sources I have seen on this equation define it as such. —The preceding unsigned comment was added by 24.42.196.192 (talk • contribs) 21:34, 3 December 2004 (UTC)

Right, that got fixed shortly after your comment. Dicklyon 02:24, 30 May 2006 (UTC)

This a very interesting article! ^_^ —The preceding unsigned comment was added by 70.17.37.126 (talk • contribs) 19:24, 30 April 2006 (UTC)

Please sign your comments with four tildes as the editing talk page suggests. Dicklyon 02:24, 30 May 2006 (UTC)

[edit] Equation

Shouldn't the equation be Color * Diffuse + specular and NOT Color + Diffuse + Specular? Starfox 23:40, 25 July 2006 (UTC)

which equation are you referring to? Dicklyon 07:00, 26 July 2006 (UTC)

Perhaps the confusion is the ambient term? k_a is the ambient colour, k_d and k_s are diffuse and specular. There are actually three different colour terms, each making a contribution to the lighting. Neither of the formulae you suggest represent what is currently on the page, or proper Phong lighting, though the specular colour is often very close to white, which may be why you have omitted its multiplication by colour in your suggestion. - Rainwarrior 07:28, 26 July 2006 (UTC)

Ah, I see it. The confusion is the picture diagrams below where the diffuse colour has been combined with the ambient colour. The "diffuse" picture should have colour to it, and the "ambient" picture should be much darker. I'll see if I can fix it. - Rainwarrior 07:31, 26 July 2006 (UTC)

Oh, right, the funny picture equation. It's not well explained, but if you interpret the text below it, where it explains that it's a gray object in a blue ambient environment, I think you'll find that it's not incorrect. It could certainly be improved, though. Dicklyon 07:39, 26 July 2006 (UTC)

Ah, didn't spot that. Well, I edited the image as best I could to be a more traditional example where the diffuse and ambient colours are the same. - Rainwarrior 08:03, 26 July 2006 (UTC)

I don't think they add up to the left-hand image now. Maybe we should contact the guy who did it in the first place to do it over better. He probably has a programmable way to do it. Or write one, using a new object, maybe even with more than one color. Dicklyon 19:12, 26 July 2006 (UTC)

Yeah, I couldn't get the colours quite right (my graphics editor didn't have the right controls for colour, I tried to approximate). I could rig up a demonstration program and redo it later. - Rainwarrior 21:21, 26 July 2006 (UTC)

I think I might be able to provide some pics on the classic teapot. I can do a simple GLSL shader in RenderMonkey. Interested? Starfox 23:02, 26 July 2006 (UTC)

Sure, go for it. - Rainwarrior 23:20, 26 July 2006 (UTC)

I can redo the image with the correct idea and more than one color, thanks for the corrections. - T-tus

I don't know if Starfox is still planning to do this or not, but I wrote a little software renderer and made a new image out of it. Looking at it now, I wish I'd used a more curved surface like the original version so there'd be more interesting specular highlights, but for now this at least is accurate, colour wise. - Rainwarrior 04:16, 7 August 2006 (UTC)

I hacked my raytracer to do some sort of ray-blob intersection (it was surprisingly tricky...), and made a new version of the image using a much curvier (and more specular) model. - Rainwarrior 18:09, 7 August 2006 (UTC

[edit] Phong shading

See talk:Phong shading for why we are keeping these as two separate pages, and what we are trying to do to make it work better. Dicklyon 17:13, 30 May 2006 (UTC)