I want a reflective surface to be lying on the ground (a mirror, no frame, just mirror). I am using P6 and below is my setup. I've made sure raytracing was on for rendering but all I'm getting is a black square with NO relections on it. Any ideas? Thanks in advance. Kristta

diffuse colour should be white i think

um, i went to try to reproduce your problem and noticed you dont have a "normals forward" check box on your materials and your reflect is missing the RayBias setting. do you have the latest sr installed? other than these diffrences, my reflection shows up. make sure the items you want to reflect have the "visable in raytrace" checked in the properties tab. if the things you want to reflect are only seen in reflection (they are not within the direct field of view of the camera) then you must only use raytrace shadows or turn shadows off

The diffuse value and the reflection value should add to 1, so if you want 0.9 reflection then you should have 0.1 diffuse. Also, what do you have above your floor? It won't reflect anything unless there's something there for it to reflect.

@ ajax If you split relection/refraction at say, 0.6/0.4, what happens to the diffuse value setting? Is it still 0.4 ?

The sum of all three ought to add up to 1. Basically, you want all of the light coming off a surface to add up to 100% or less of the light that hits it, unless the surface is glowing or something. Real life isn't quite that simple of course, so the rules aren't hard and fast, but the idea is that if you shine a light on a surface, some light may be scattered diffusely by the surface (that's the diffuse component), some may penetrate the surface and be bent by it (that's the refraction component) and some may be reflected coherently by the surface (that's the reflection component). Some light may be absorbed by the surface and converted to heat (effectively that's light that gets lost). When you add up all those different amounts of light, the sum shouldn't be more than the amount of light you shone on the surface in the first place, so the components should add up to 1, or less than 1 if some of the light is being absorbed. If you use ambience as a sort of fake global illumination effect (to light up areas that aren't directly hit by light, as though they were being hit by scattered light from other objects in the scene), then you should include the ambient value in the sum as well and make sure the whole thing adds up to 1 or less. If you use ambience to create a glow effect, then it doesn't count toward the sum.

Minimal set-up for reflections... Just a 1-sided square with a ball. P6 SR2. Cheers, Diolma

What settings should be used for a "perfect mirror"? I'm trying to do a scene with a bathroom mirror and it always comes out looking like the relfection is more off a window, rather than a perfect mirror image?

The latest image in my gallery is the one that I used the mirror on. I can't pull it up here at work cause it does contain nudity. I got it working though. Thank you all for your help.

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From Richardson: "If you split relection/refraction at say, 0.6/0.4, what happens to the diffuse value setting? Is it still 0.4 ?" Reply from Ajax: " The sum of all three ought to add up to 1. Basically, you want all of the light coming off a surface to add up to 100% or less of the light that hits it, unless the surface is glowing or something." Errm - no, not quite. (I suspect that Ajax had "ambient" on his mind when he wrote that reply...) Refraction has very little to do with reflection, except in very special circumstances. Refraction is the amout by which light changes direction when entering/leaving a surface with transparency. Hold a pencil (or whatever) in a glass of water and look at it from an angle. The pencil seems to bend (abruptly) where it enters the water. It does this because the refraction index of water differs from the refraction index of air. Reflection is light being bounced off a surface. Since the light doesn't actually enter the surface (assuming total reflection), refraction doesn't enter the equation at all. There are times when it does, but that's usually only required for very close-up images... Cheers, Diolma

Diolma, I suspect you're thinking about the refractive index, rather than the refraction value. The refractive index does indeed govern how much direction change is experienced by light as it passes through the surface and doesn't enter into the equation I gave above. The refrative value on the other hand, measures the proportion of the overall light striking a surface that manages to pass through the surface in order to be refracted. This has everything to do with reflection under all circumnstances, in that any light which doesn't pass through the surface and become refracted, winds up either being absorbed or being reflected (either diffusely, which is the diffuse value, or coherently, which the reflection value). So I stand by my statement: Reflection Value + Refraction Value + Diffuse value < (or =) 1 This is why, when you look at an ordinary piece of window glass, you can both see your own reflection and be seen (refracted) by a person on the other side of the glass. Some of the light that comes off you and goes toward the window gets reflected back to you and some gets refracted through to be seen by a person on the other side. A very small amount is absorbed by the glass and then radiated as heat. If it's still not clear, let me know and I'll try and put together a diagram.

LOL, Ajax, you are absolutely right. But that's why I said
"There are times when it does, but that's usually only required for very close-up images..."

In the vast majority of cases, refraction doesn't come into it (in image production terms). After all, how often do you create an image that sees both sides of a piece of glass?

I'm not talking strict physics here, only practical image production. Usually, refraction can be ignored for reflective images. If you have an object passing through an object that is both (to some degree) reflective and refractive then both come into the equation and might need to be taken into account. If in close-up. Depending on the material. Taking glass as an example, the difference can't really be seen from more than a few feet away (I think - not sure about that: not seen many real-life examples of pencils embedded in glass..).

As for water, well (no pun intended), yes, the eqation needs to balance. If, that is, you're going for a super-realistic image (and extended render times)..

I apologise. My previous post was based on a pragmatic approach, not a detailed one. I should have made that clear.. But the thread was about mirrors, so that's how I responded...

Cheers,
Diolma

Message edited on: 02/10/2006 15:55

??????? So let me get this straight. You actually quoted Richardson's question from post 5 and part of my answer to it, so you know he was specifically asking about an unspecified substance with a high degree of both reflection and refraction but you feel that a "pragmatic", "pratical image production" answer to his question would have been something along the lines of "Just use a mirror - I know you asked about something with a 0.4 refraction value, but in the the vast majority of cases that's not relevant except in close up images - after all this thread is about mirrors."? I'll stand by my original answer to his question, thanks. I think that's about as pragmatic an answer to the question he asked as you could have. It was a much more timely answer too, given that it was posted nine months ago. "In the vast majority of cases, refraction doesn't come into it (in image production terms). After all, how often do you create an image that sees both sides of a piece of glass?" Apparently I should have left out the glass window example since it seems to be confusing the issue. Now it's there, I'll try to explain it a bit better. While you may not be seeing yourself through the glass, you can bet you are seeing some things that are on the other side of it. Some of the light from those things gets reflected back toward them. This reduces the amount of light that you see from them, dimming their image. If you fail to take account of this, you'll wind up with a window that has more light coming off it than the amount that was in the scene in the first place. In "practical image making" terms that means your object (whether it's a bathtub full of water, a block of glass or an aquarium) will look wrong, appearing to be washed out and/or glowing. So how do you take account of it? In strict physics terms, the proportion of light that gets reflected/refracted depends on the angle at which the light strikes the surface of the object. It's pretty hard to do that accurately in Poser. The pragmatic approach is to make sure that the sum of the reflective and refractive values of your material add to 1 (assuming you want a completely transparent material with no diffuse component). The underlying assumption (i.e. fudge factor) behind this approach is that the proportion of light coming off objects on the other side of the window that manages to get through the window and come toward you is the same as the proportion of light coming from you that manages not to be reflected and to go out through the window. So it's not a question of how often you see both sides of a piece of glass, it's a question of how you get a believable amount of light coming from a transparent object in your scene. Given how many e-mails I get asking about this, I wouldn't say it was a particularly esoteric topic. It seems there are a lot of people out there interested in rendering nekkid vickies in a pool or a bathtub or looking into an aquarium and who want both the reflection and the refraction.

Ajax:
The original post:

" I want a reflective surface to be lying on the ground (a mirror, no frame, just mirror). I am using P6 and below is my setup. I've made sure raytracing was on for rendering but all I'm getting is a black square with NO relections on it. Any ideas?"

That's what I was responding to.

All I was saying was that your posts, 'tho informative, weren't adding to the original post. I admit I also got drawn in deeper than I should have, but was just trying to say that for mirrors (not water, not glass, not even semi-translucent objectoids from planet xenox, just mirrors), that's all you need to concentrate on.

I'm not attacking you. I agree that you know your physics regarding water reflections.

Ah, well... Sorry if I caused offense.

Cheers,
Diolma
Edited to add: I didn't notice how old the thread was. If I had, I wouldn't have responded in the 1st place...

Message edited on: 02/11/2006 18:02

Well, I gave my answer to the original post in post 4 so when richardson asked his question in post 5, I didn't see any harm in answering it, even if it was a bit off the topic of the original question. Sorry if we offended you by opening the question up to a topic wider than that of mirrors.

NP, Ajax - I should have read the dates etc. more carefully. I wasn't offended, I was just (originally) trying to keep the thread on-topic. Which is why, if I'd noticed the dates, I wouldn't have bothered:-) (Note to self: CHECK THE DATES!) Cheers, Diolma