Refelction, Specular maps

[rhyzx]

this is something else I have not been able to get to work. I'm trying to follow this tutorial
http://www.cg-blog.com/index.php/201...n-map-wood.htm

it is for 3ds max but it should apply to rhino too. Specular and refection maps don't have any or similar effects, no matter where i apply them. i have placed them in: maps: reflection, glossiness: hilight, glossiness: reflect. is there a tutorial on this for rhino?

[fooprobe]

well it won't work in glossiness hilight/reflect. glossiness controls how sharp or blurry the reflection is, not the amount of reflection.

the map belongs in the reflection parameter. you can either use it directly, instead of the default fresnel map, or you can put it in the "perpendicular" parameter inside the fresnel map:

[rhyzx]

thanks exactly what i was looking for. i noticed i works on the parallel map.

[fooprobe]

That makes sense... I would guess that using the parallel parameter would make the reflection have less of the fresnel effect - so it would be similar to using just a bitmap instead of the fresnel map. Ill try to test it out.

[fooprobe]

so i decided i had to really understand the difference and did some tests. the following is a sphere with a simple gray material with the default reflection layer:


you can see it exhibits the expected fresnel reflection, where the reflection is weaker in the middle of the sphere and stronger at the edges (it's not just the darker sky - look at the brightness of the white ground plane at the bottom center of the sphere, compared to the upper right and left edges) ... for comparison, here is the same material with the fresnel map removed from the reflection parameter (so it uses a uniform white color):



since the color is applied uniformly, the reflection is consistent (and strong because it is white)

so here is the original material, with the default fresnel map, but then adding a texture to the perpendicular parameter inside the fresnel map:



so we get the same fresnel reflection, but then the dark colors in the texture reduce the reflection further. by comparison, here is the same texture in the parallel parameter (and removed from the perpendicular parameter so it is just white):



the fresnel effect is basically removed. this is because the reflection value is increased everywhere to white, except where the map has dark colors. so it approximates having no fresnel map. for comparison, here is the material with NO fresnel map in the reflection, but instead of a uniform white color, the texture is used:


almost the same, just a slight difference at the edges.


one thing i don't understand about the fresnel map is the naming of "perpendicular" and "parallel" - intuitively i would expect that this means the color or map would affect the reflection on surfaces that are either perpendicular or parallel to the camera, respectively - however the effect is the reverse: when perpendicular is white and parallel is black, the center of the sphere (surfaces perpendicular to view) reflect less and the edges (surfaces parallel to view) reflect more. maybe someone at chaos group has some insight into this?

[rhyzx]

I wish I could see the images but I understand what you are trying to show. I think there are other parameters where black and white have the opposite effect of what one would expect. Could be displacement or bump I can't remember.

[Micha_cg]

For an effect like at the linked tutorial (wood) you need to place the map at the perpendicular color of the fresnel options. So, the power of the fresnel reflection is controlled by the map.