Exterior | Rendering vegetation comes out dark

[Helldoor]

Hi there,


I have a problem, rendering some nice, sunny trees in my exterior scene. I use Vray Sun (CIE Clear) and Sky (in GI and BG), also LightCache for the Seconday Bounces. Color Correction is Reinhard with Gamma 2.2. What I try to achieve is a sunny summer scene of a house, using 3d vegs - trees and bushes. However, the Trees come out pretty dark, compared to the very bright house. If I push the preferences - the Sun, for example - in order to become a nicely lit tree, the house becomes washed up in color and gamma.

I attach two images - of the tree, that I use and of how it comes out in my render. You can easily see the differences. The scene is far from being ready, but I'd really like to light it up properly at this point.


I'll be glad to hear how you'd deal with this. Thanks in advance.
Helldoor

[fpedrogo]

Hi
Part of the problem is the position of the sun. I the image of three the sun is coming from the front side of the three, giving you a nice illumination. While in the render of the house, the sun in coming from behind the three, so you will have a lot of shadows in front of the three. Another thing could be the three's material. Can you pack the scene and send it to me? I will look at it and give you a precise solution.

[Helldoor]

Thanks. That'd be awsome. I wrote You a personal message for the contact.

[fooprobe]

If your leaves are an image rather than a plain color, you might try making sure that linear workflow is turned off and correct rob colors and correct ldr images are both turned on (OR go do your post processing correctly).

otherwise it looks like your GI skylight is too dark. You have blue in the shadows of the tree alone, but not as much in the one with the house.

[Helldoor]

If your leaves are an image rather than a plain color, you might try making sure that linear workflow is turned off and correct rob colors and correct ldr images are both turned on (OR go do your post processing correctly).

Yes, my leaves contain images. Could You be so kind and shortly explain why linear workflow is not good in this case, resp. why 'Correct LDR textures' or 'Correct RGB Colors' are more appropriate?

otherwise it looks like your GI skylight is too dark. You have blue in the shadows of the tree alone, but not as much in the one with the house.

The GI Skylight is directly connected to the Sun. I thought, that the TexSky, being procedural, couldn't be wrong - too dark or too bright, as it is set automatically. Am I wrong?

Thnaks for the responce!

[fooprobe]

You can still adjust the multiplier on the GI skylight, even when set to TexSky. Nothing is really automatic. And "wrong" is when something looks wrong, not when an algorithm says so. So if your shadows look too dark, increase the skylight multiplier.

linear workflow... It depends on how you have things set up. If it's on it means that non HDR textures, and RGB colors, won't have color mapping applied. It's expecting that you are not correcting your gamma with vray, that you are working with non-gamma-corrected maps, that you will save renders as 32-bit files and you will apply correction as needed in post. So if you aren't doing any of that, but you leave it on, these images can sometimes appear with the wrong saturation, either too washed out or too dark. Often renders look just fine without touching this, but sometimes it's a problem - it depends on whether the images have already been gamma corrected. I always turn it off and the other switches on because I prefer to let vray handle the gamma correction. I have no idea why it's on by default.

There's a good (maybe too good) explanation of this at the link below, though it's for 3DS max, it's the same idea. Note that this link talks about using linear workflow, but it shows the "linear workflow" switch as off. Confusing.

http://www.aversis.be/tutorials/vray...orkflow_01.htm

all that said, it may not be your problem.

[Micha]

First I don't like the physical sky so much, the naming of the options and the the places where to control are confusing. Often I try to use a HDRI + a dir light.

I started a test of the physical sky today. For your use, I would recommend to get a brighter sky. This can be done per lower the intensity of the sun and increase the general brightness of your scene per physical camera or color mapping multiplier. Sun intensity 0.5 could be a good value.

Also I like a warmer, smoother sky look, increase the sun size at 10 and turbidity at 4 for a warmer mood.

Color mapping - input/output gamma at 2.2 and LDR/color correction enabled.

[Helldoor]

Thank you very much - for the explanation and the link.

Of course, the 'post' phase is a very important one for every project I'm working on. Usually I add there all the vegetation, people, sky, adjust the lighting, etc... By this certain project however, the time I have for the post-production in the end would be very limited. That's why I try to achieve balanced images in vray, so the editing won't take long afterwards.
I'll try it out with the Color Corrections.

Greetz
Helldoor

[Helldoor]

Hi Micha,

thanks for your responce too!

After fooprobe's suggestion I quickly tried out, switching on the LDR/RGB Color Corrections. It makes the leaves a bit brighter, however it totally washes up some of my other textures. I guess I should keep the linear workflow for this project, as the time pushes. But in future I'd probably always use the other two corrections, you two proposed. That's also the first time I work with a TexSky - I found it simple and ok for the certain purpose.

I've probably found a workaround for the dark trees. Soon I'll post a pic.

[Helldoor]

So,
in order to brighten up the trees, I simply made the leaf image maps in PS brighter. Also I use a diffuse value of 1.25 for the leaf. And last - I converted the leaf maps into transparency maps (also in PS - desaturate, invert colors, play with tones) for the map in the Leaf 2Sided Material.

That's the result. Maybe it's not optimal, but it's a good base for the post in PS:

[fooprobe]

Looking better. If you do like to save 32bit and do color correction in post, you can keep Micha's settings and then use "don't affect colors". You will get a usable image but avoid problems with your maps.

[Helldoor]

Thanks for the tipp!

[fpedrogo]

If your leaves are an image rather than a plain color, you might try making sure that linear workflow is turned off and correct rob colors and correct ldr images are both turned on (OR go do your post processing correctly).

Correct LDR texture correct the gamma for all the textures in the scene and Correct RGB colors correct the gamma for all the colors in the scene. So, you can control the gamma for textures and color separately. The linear workflow control both the textures and colors at once. Both produce the same result. The only real different is that with Linear workflow you can not control the input gamma, but with Correct LDR textures and Correct RGB colors you can manually control the input gamma.
There are an exception with the emissive materials and lights (including dome light). We do not correct the gamma for those. The reason is because you should be using images with gamma 1 (HDRI). If you are using regular images, you will have to manually correct the gamma for them. So, if you have a dome light in your scene and you are using Correct LDR Texture and Correct RGB color the gamma is not perfect. You will have a litter brighter result. But again, both method should produce the same result in term of general gamma if you are not touching the input gamma.
Another exception is the translucent materials, the linear workflow work better for those materials. If you use Correct LDR texture and correct RGB color, they will looks darker.

[fpedrogo]

Hi Helldoor
This is my example with your scene. The 2sided material tends to create darker result. we need a brighter light to get the result in the Three image that you posted. What I did was use translucent in the material. Because the translucent effect is very subtle, the render is fast. Also I made a test with Linear workflow vs Correct RGB color and Correct LDR texture. My recommendation is use Linear workflow.

This is the correct LDR texture and correct RGB color. Notice that the three is darker due the translucent issue with the gamma correction mode. Also, the windows frame and reflection are brighter due the same issue with lights.


This is the image using Linear workflow. Notice that the gamma is good everywhere. The three is brighter and the windows frame match the gamma of the dome light and material.
I just adjust the material itself without any photoshop. I though that was what you wanted to do.

Notice that the gamma is the same with both method. Of course with the exceptions that I mentioned.