Grass mtl

[mav3rick]

i'm trying to make grass material any advices?
diffuse map + brighter translucency map (fraction=0.15)

here's render tests
grass-vray - 2sided from Vray, secend is corona test (on top reflection level=0, middle RL=1 IOR=1.1, bottom RL=1, IOR=1.25)

[Ludvik Koutny]

IOR does not affect translucency in any way, and you should never use refraction for grass. Create new material with default settings, plug your texture map into diffuse slot and instance that same map into translucency slot. Set translucency fraction to about 0.4-0.6. Then simply tweak reflection of your material, and use reflection glossiness map for best results.

[vkiuru]

IOR does not affect translucency in any way, and you should never use refraction for grass. Create new material with default settings, plug your texture map into diffuse slot and instance that same map into translucency slot. Set translucency fraction to about 0.4-0.6. Then simply tweak reflection of your material, and use reflection glossiness map for best results.

I find it handy to put the instanced diffuse texture map into a color correction node so you can increase the saturation and brightness of the translucency slightly.

[Ludvik Koutny]

IOR does not affect translucency in any way, and you should never use refraction for grass. Create new material with default settings, plug your texture map into diffuse slot and instance that same map into translucency slot. Set translucency fraction to about 0.4-0.6. Then simply tweak reflection of your material, and use reflection glossiness map for best results.

I find it handy to put the instanced diffuse texture map into a color correction node so you can increase the saturation and brightness of the translucency slightly.

True, but i did not mention it so that i do not confuse the guy further ;)

Actually, translucency texture carries both color and translucency intensity, so if you want translucency amount to vary based on map, then in color correct node, increase contrast of your translucency map, and then compensate back the saturation gained by increasing contrast. That will give you a more interesting and pronounced translucency effect. I often shift my translucency map using CC node little bit to the yellowish tones, but i would not increase saturation, as that would probably decrease realism. Back sides of leaves are sometimes less saturated than front ones, but almost never are they saturated more. If you see a picture of a nice saturated leaf from the back side, it is most of the time enhanced in something like PS, and also distorted by colored sunlight shining on it.

[mav3rick]

IOR does not affect translucency in any way, and you should never use refraction for grass. Create new material with default settings, plug your texture map into diffuse slot and instance that same map into translucency slot. Set translucency fraction to about 0.4-0.6. Then simply tweak reflection of your material, and use reflection glossiness map for best results.

Thx :) will try it.
reflection IOR affects reflection, it was set by color=white level=1, glossiness and IOR. in setup change reflection IOR, not refraction ;)

[agentdark45]

In to see the results!

[jjduncs]

So much quicker than vray for this patch of grass with forest.
vray took about 7 minutes while this looked fine after about 2 minutes.
Just wondering about the DOF, the specks in the background from their reflectivity dont seem like they should (possibly more blurry out of focus?), what setting will help these out?

[Ludvik Koutny]

High exposure areas like super-strong reflection of sundisc always tend to create sharp edges even in Blurred areas, as the highlight area is many times brighter, not just clamped white, so it creates sharp fringe, like on this photo:



To increase clarity of DoF, you can decrease PT samples, that means less samples will go to the secondary effects (reflection, refraction, translucency, GI and such), and more of them will go into primary effects (antialiasing, DoF and Motion Blur). So try set PT samples to somewhere around 2 to 4.

Also, people often create a bit more reflective materials than they really are. So make sure your grass does not have too high reflectivity, or too high glossiness. Grass is not as reflective as it may seem, unless it is wet after rain ;)

[jjduncs]

Yeah thanks, i think i had my glossiness too high. Turning it down made the highlight bokeh much smoother.

[Alex Abarca]

I started this topic and it turned to Grass Mat too. Check it out.

http://forum.corona-renderer.com/index.php/topic,2784.0.html