Something AgentSmith mentioned in an earlier post: "Sure, the air between two non-transparent objects can have refractive properties. (but I'm not sure if you would see any difference in Byce if you did this) (scene enveloping cube with refraction?)", stirred the experimenter in me, so I built the following set-up (seen here in top and side view wireframe. The sphere was just to see if refraction would have an effect on objects in the cube. NOTE: Please refrain from commenting until I get the whole deal uploaded. I'm on a slow connection and would like to have this flow as there are 4 or 5 pics. Thanks.

Here is the first image. The texture settings for the cube are imposed in the right lower corner.

An increase in the refractive setting, now the cube is casting a shadow.

As refraction is increased past 200, a weird disc shape begins to form.

And finally at the max refractive setting of 300, what appears to be a 2d disc in the picture, and is obviously (to me anyway) closer to the camera than the back wall of the cube, and there's still not much effect on the red sphere other than making it a bit darker. The back wall of the cube is showing an interesting pattern as well. I swear I'm not playing tricks on you, this is just as I'm describing it to you. John This is the final image. Thank you for waiting.

Whoa! Awesome! Is refraction really volumetric? I had always assumed that it was just like that when viewed from the outside. cool!

Looking at it again, I believe the disc shape is at the same position as the back wall, it just seems at first glance to be closer.

An interesting topic and experiment... beyond just making pretty pictures... I am fascinated by the intricacies at play here... clearly there is much fundamental and radical reevaluation to be achieved through a critical imagination.-Susan

Message edited on: 09/01/2004 11:57

I don't think that's what agent smith meant. all this is doing is changing the refraction index of the world around us.. in most cases this is Air.. which has a refraction index of 1. It's probably higher when taken in relation to a vacuum, however, we use this as our basis and therefore the refraction is and always will be 1... This again shouldn't have any effect on non transparent materials. But if you stuck a sphere in there and made the refraction 1.33 and the refraction of the cube 1.33 the sphere should become invisible. This is all you are doing in a non photon based rendering engine.. changing the relative refraction incidents.

Also, refractions in bryce are not volumetric, therefore putting the camera inside the cube only effects the refraction of objects outside of the cube.. so the sphere is not changed at all even if it was transparent... In order to effect the light that gets to the sphere, you'd have to put the cube around the sphere and the camera outside of the cube.

Well, maybe only AS could clarify for sure, but: "(scene enveloping cube with refraction?)" sure sounds like enveloping a scene with a cube with refraction settings applied, and that's what I did, maybe I am misinterpreting. But nevermind that, I still think this was a pretty weird (and for me, weird is almost always interesting) effect. :^)

But what does it accomplish? It bends the sky and everything outside of the cube, it has nothing to do with anything inside the cube.

Gee, Ornlu, what's wrong with my finding this interesting? An almost perfect disc shape appears in a maxed out refracted cube with a camera in it. Did you know it would do that? I didn't. Now I do. I learned something unexpected today. I'm sorry that it seems to offend you. :^)

Refraction works better with spheres or cylinders anyways. Try putting the camera inside one of those and place the subject outside. Then play with the settings for some interesting fun.

Sorry tjohn I didn't mean to offend you either.. And I wasn't. I was just curious as to why this was pertinent to the refraction concept that everyone's trying to push.

No offense taken, it was just an experiment with refraction spurred by the earlier post. That was the only pertinence it had. I thought it had a fun outcome, that's all.

@ tjohn: Nice observation, but that works only with primitive objects in Bryce, polygon mesh of the sphere(or cube) will not work, I already tested that (looks that only "render effect" objects, which primitives are, indeed, have volumetric type of refraction, meshes are considered as 2d surfaces in space, as beeing hollow inside). @ Ornly: It is relly not "pushing" things, i believe, were are all just trying to figure out certain aspects of Bryce and it's ray tracing algorithm, cuz it's tottaly undocumented and misterious, looks to me that it's not that simple as some other ray tracing engines... Call me crazy, lol, but i tend to believe that there is a lot of things we do not know happening behind that simple and ellegant interface Bryce have !!! :)

From what i've heard the bryce code is extremely messy lol. The bryce rendering engine is actually much less complex than most other engines. It's more reminiscent of a first generation POVray clone with a great UI.

Holy C**P No, that's exactly what I meant, I didn't think it would EVER really do anything though. Lol... Hey, have you tried changing the TIR or MRD? (just for giggles) AS

Yup, changing the TIR and MRD will change the effect. So will taking the cube and booleaning it out hollow with another cube. Which I know it is hollow to begin with really, but the effect changes with the booleaning... AS

I told ya !!! :)

I compare the 3D environment to the real world environment.

Every one know that refraction is the bending ( direction shift ) of light as it passes through a transparent, or semi transparent object. But why does the light bend? The light bends due to a change of speed that the light is traveling at.
The direction it bends depends on the optical density of the objects it is passing from then into. When light passes into a denser object it slows down and it direction changes towards the normal. When it passes into a less denser object it speeds up and bends away from the normal.
( The normal is an imaginary line, passing diagonal through the object from the entry/exit point of the light,) Refraction only occurs at the boundary of the object.

Example: When light passes from the air into a crystal ball it slows down and is bent towards the normal as it enters the crystal, then it travels in a strait line through the crystal ball, then it bends away from the normal as it exits the crystal ball and speeds back up as it enters back into the air.

That's why there is no Refraction Channel for volume materials. Because refraction is not a volume property.

The Bryce environment is set at 100 percent refraction, that's why the refraction channels 100 is called air. Any setting above 100 should bend light towards the normal, any setting below should bend light away from the normal. ( but it does not )

"Sure, the air between two non-transparent objects can have refractive properties.(but I'm not sure if you would see any difference in Bryce if you did this "

Yes the air has refractive properties, but if light is not traveling between an optical dense boundary, refraction will not occur.

" But if you stuck a sphere in there and made the refraction 1.33 and the refraction of the cube 1.33 the sphere should become invisible."

No, you just would not see any refraction because there is no optical density boundary change.

"So will taking the cube and booleaning it out hollow with another cube. Which I know it is hollow to begin with really, but the effect changes with the booleaning..."

Because you are actually having the light pass through the object, it goes in than out the thin wall of the boolean. So you are really inside an environment that is Bryce's 100 percent air. Where if you are inside a cube that is not boolean, then you are in an environment which is set to whatever the cube refraction setting is.

" An increase in the refractive setting, now the cube is casting a shadow."

Yes because you are making the optical density denser. So the cube lets less light in. and cast a shadow with the light that does not penetrate into the cube. The denser the optical properties become the less light is let in, thus the spherical shape gets small as less light travels through the cube and exits out the rear.

This effect does not work the opposite way because there can not be more light let in than the surrounding environment lets in. In other words if the air is 100 percent refraction and the cube is 0, more light can not be let into the cube, than is present in the 100 percent surrounding environment. ( But if it could wouldn't that be a great way to fake GI )

Where I see the Bryce ray tracing algorithm flawed, for refraction is. The light should shift direction depending on the optical density properties. But it does not. Sure when you set refraction lower or high than air, you will see an opposite shift change on the surface of the object. But the light passing through the object does not shift in direction. In tjohns demonstration here the shadow on the sphere stays located at the same place no matter what the refraction is set at.. Where in reality the light should be shifting direction more as the refraction gets denser. I bet if the refraction was set to 0 for the cube the shadow would still be in the same location even though it should shift because the light in the real world situation is being bent in the opposite direction.

As far as I knew, the normals on refraction diagrams were depicted perpendicular to the surface. "That's why there is no Refraction Channel for volume materials. Because refraction is not a volume property." Well you're right and wrong here. Refraction is in essence a property of a volume. If it were not, then refraction would simply not exist. Refraction in the real world needs a solid medium to travel through. Take glass for example. If glass were only a minutely thin shell with glass - air - glass then refraction wouldn't occur... This is not true in bryce because 3d objects are in essence shells. Because of this bryce has to cheat. It takes the theory of refraction and applies it to the outer surface of an object. I think most applications do this as well. "" An increase in the refractive setting, now the cube is casting a shadow." Yes because you are making the optical density denser. So the cube lets less light in. and cast a shadow with the light that does not penetrate into the cube. The denser the optical properties become the less light is let in, thus the spherical shape gets small as less light travels through the cube and exits out the rear." Also not true... A more refractive material appears darker because of the way light is being bent at the surface of the material itself. Because light is being bent so much when it strays from entering the material at a perpendicular angle there are less incident 'light beams' interacting with all areas inside the sphere/cube whatever. Subsequently there are also denser areas of 'light beams' inside of the sphere because of this. This is not due to less light penetrating the surface. This is caused only by hightened opacity and reflective properties.

"" But if you stuck a sphere in there and made the refraction 1.33 and the refraction of the cube 1.33 the sphere should become invisible." No, you just would not see any refraction because there is no optical density boundary change." my point was... if the objects were made of the same material or equally transparent materials of the same color with identical refraction indexes the inner sphere would not be visible from outside the cube or half way into the cube / whatever in the real world. In bryce.. this won't work and especially won't work once inside the first cube as it will ONLY refract light coming off of objects outside of it (which is not really how bryce works but anyway... that's my point). Bryce's function for refraction is actually entirely reversed from real world physics... rays are sent out from the camera's location and interact with the other objects/transparancies... it's all complex and confusing and can't be compared to REAL world physics in all cases.

"Bryce's function for refraction is actually entirely reversed from real world physics... rays are sent out from the camera's location and interact with the other objects/transparancies... it's all complex and confusing and can't be compared to REAL world physics in all cases."

That's true, Ornlu. Just as some of the more current renderers today can handle light a bit differently than raytracers like the one Bryce uses in that they can calculate photons of light starting at a light source, which can then be bounced off mirrors, etc., to more accurately simulate the way real light behaves (not that this is any kind of revelation to anyone, just thought I'd mention it).

I'm sure the next major upgrade to Bryce will have all kinds of additions to the renderer that keep up with the current state of affairs in render technology. ;-)

However, if they give Bryce GI capability, at least give users the option to calculate realistic GI in other (faster) ways like photon mapping/light mapping. hehe. Radiosity is great, and can do wonderful things for interior scenes, but it's not the ONLY meathod out there to calculate high quality GI, and in my opinion, not the most efficient. Message edited on: 09/02/2004 08:59

"I'm sure the next major upgrade to Bryce will have all kinds of additions to the renderer that keep up with the current state of affairs in render technology." That will be "Super Bryce" (Bryce 6.0) AS