OTOY Forums

OK, I'll bite Paquito

When you say 'distort to the silloette of the shap' are you talking about how the reflection at 0 is in a different place/different shape to the one at 8?

Isn't that because the one at 8 is in a different position, so the reflection is different. I'd be interested to see what happens if you make the one that is far left 8, and the one on the far right 0

Thought I'd run this little test.

It definitely a Fresnel effect. Above 1, the reflection is only there based on a certain angle of incidence. Cant really see a difference about about 5 though. 1 or lower, it's disabled.
Perhaps when when you look at IOR data, it's got numbers for things like metals etc. I'd always assumed it was when they were in gas or liquid form, but it must be the reflection.

You can see the test here...

[youtube]http://www.youtube.com/watch?v=3wYqhMIrnqI&feature=youtu.be[/youtube]

Just Prefect!! Great!! light and texture.. like it!!!

gordonrobb wrote:OK, I'll bite Paquito

When you say 'distort to the silloette of the shap' are you talking about how the reflection at 0 is in a different place/different shape to the one at 8?

Isn't that because the one at 8 is in a different position, so the reflection is different. I'd be interested to see what happens if you make the one that is far left 8, and the one on the far right 0

I´ve just made a test and you are definitely right. The reflections distort due to the difference in placement of the balls. Now if you place a single ball, making it full specular, no roughness and go sliding the index from 1 to 8 back and forth you will se the real effect. The reflections at low index gets visible only at a high incidence angle, while the front view of the ball is still non-specular. While you move the slider -raising the value- you will see how the front of the ball starts throwing reflections (more visible the more index you set).

In conclussion: index doesn´t make distortion of reflections, it only keeps the reflections restricted to an incidence angle of the viewer. The less the index, the more restricted are the reflections, thus a high index value gives full reflection (decreasing diffuse) and a low index value gives weaker and more "side reflections" (increasing the visibility of the diffuse color)

There seems to be a special rule for values from 0 to 1. This range seems to give full specular. A value of 1 is no specular at all, and it goes normal from there.

visuall wrote:Just Prefect!! Great!! light and texture.. like it!!!

Great compliment coming from you, visuall. Thanks

Yes Paquito, did you see my video?

Now, the next question is what the hell does the number mean. T'internet says that the fresnel effect is dirven by the IOR or the material (Index of Refraction), even though it's a solid. However, if you look up the IOR of Chrome for example, it is 2.97 which when you look at it, does not look that realistic.

Maybe the index slider in Octane is just a slider and the number doesn´t relates to the IOR of the material.

That would make sense if not for this extract from the manual, under 'Index' setting in Glossy textures.

Index of Refraction: Index of refraction sets the fresnel effect applied on the glossy material. Setting a value smaller than 1.0 will disable the fresnel effect, so the glossy colour will be the colour in the glossy input pin, regardless of viewing angle. When selecting a value of 1.0 or big­ger, the glossy reflection color will be modulated according to the fresnel law: at grazing angles the color will be the color set in the glossy input pin, at perpendicular angles it will be darker. Fresnel reflection produced becomes stronger as the index of refraction is set higher. If you have a measured index of refraction, set the glossy colour to 1.0.

However, that is not clear, as what the hell is the 'glossy colour'. As far as I can see what this is affecting is the specularity based on incidence angle, cant find anything about glossy colour. Wasted hours looking into IOR and reflections and as fun as it was, and as sore as it made my head, I'm none the wiser

A little help from someone who actually knows what Octane is doing would be nice