View Full Version : What's wrong with this picture?

06 June 2009, 05:16 PM
What aspect of the render quality of this 3D scene makes the tree trunks look as if they're floating in the scene and not really "there"? I am trying to get a handle on what makes a photo-realistic image and what does not.

You probably already know which software it's from but I'm not asking about that software's abilities. I am very curious as to what someone would correct in this render to give it less of the illustration feel and more of the photo feel. Is it ambient occlusion, GI... that tree trunk looks pasted in and wicked FLAT! What render process would you use if you had a very full-featured renderer to make this scene much better?

06 June 2009, 05:50 PM
It's the totality of the image I'm afraid. Actually the trees themselves aren't all that bad. If I use my imagination and in my minds eye, stuck those trees into a photograph, it would look pretty decent. Which tells me its the rest of the environment thats killing the image.

06 June 2009, 06:17 PM
Agreed, but I can't quite point to one aspect.

06 June 2009, 06:19 PM
Take the image and copy it to two layers in Photoshop.

High pass filter the upper layer a small amount.

Median filter the lower image a small amount to 'simplyfy it and lose detail'

soft light blend mode the gray high pass layer back onto the median filtered layer.

Lower saturation, but especially on greens

seems to help

06 June 2009, 06:23 PM
I there a render process that is lacking or absent that a better renderer would solve?

06 June 2009, 07:38 PM
You may want to re-work some the lighting. There is just not much contrast in the image. Everything looks evenly lit. Get a good contrast from light to dark going. This shot is very green with a lot of grass so try some green bounce light in areas closer to the camera. Also its a bright blue day so add some blue fill to help bring up the darker areas. Once you get the lighting looking the way you want it. Worry about the render passes at that point.

God bless

06 June 2009, 10:46 PM
I dont know from which software it come. I would try to use a real sky photo for the background and apply a new grass texture, maybe a camera projection from a real grass landscape would be the fastest way to do. If you want realism, nothing beat the real thing! The shape of the nearest tree is nice, the second one is a bit standard, I would try to rotate it and find a better angle. Maybe make the leaves a tad bigger with a bit of specular on them?

good luck!

06 June 2009, 12:26 AM
ambient occlusion?? might help

06 June 2009, 12:55 AM
for starters, the atmospheric perspective almost seems infinite. You have some sort of depth blur going on, but the grass is still very noisy, it should soften into a very gradual color pretty quickly. There are also what seems to be halos around your leaf sprites, might want to double check the alpha and make sure you're not picking up background pixels of the texture.

when going for realism, err on the side of desaturation. Our eyes see things and we remember them as being very saturated, which is why HDR photography is all the rage right now. But in reality, things are pretty muted. you can get away with some really saturated environments in a scene like this though, but maybe try toning it down a tiny bit.

Make sure your leaves have some sort of translucency to them.. a SSS shader would work best, but would be extremely slow. In MR I would probably just give it a touch of translucency and match the sprite's greenish/yellow hue.

for post-work, somebody already mentioned the high/medium pass trick, but I would also probably render out a spec pass and use that to create some glow, maybe a shadow pass composited on top of the beauty pass w/ multiply. those two passes on top of the beauty pass will give you a lot of nice contrast.

Now that's just the image itself- speaking to the actual contents, it's very videogame-ish. All of the trees are virtually identical, and there is no other vegitation except for the big noisy grass tile. There would be many other species of plantlife, maybe a bird or two in the sky, some rocks on the ground, trees growing closer together, etc. When I see this image, I see a single tree out in the middle of the field and I wonder how the hell it got there, and why it hasn't produced any seedlings around its base. That's how forests are made you know, seeds fall from the trees and they grow right there next to it :)

So yeah, nature is a very very complex thing, and you can do as much post-work as possible on an image like this and it will still look fake because the contents are not accurate. This image is from a video game (!!!) but look how they make it believable by making nature look complex:

06 June 2009, 02:28 AM
The shadows, in the first image, are impossible.

Look at the trees at the top of the image. Given that the shadows must be coming from "sunlight," where's the sun and how big/wide is it?

Now... the tree in the foreground. No shadows. What shadows there are, are in the wrong place.

06 June 2009, 02:29 AM
As far as the deer is concerned ... not bad, I guess, for a game, but the color-temperature of the lighting on the deer doesn't match the scene at all. It's much too blue. The right rear leg is inexplicably blown-out white.

Also, even though the light in the forest is "filtering down through the trees," the deer is evenly illuminated... in a way that seems inconsistent with where it's supposed to be standing. He's not casting much of a shadow either.

Nevertheless, there's only so much you can do in a game.

06 June 2009, 02:35 AM
I think you missed the point of my posting that image, I was merely putting it there for the variety of objects within the scene, rather than the original image that was some rolling geometry with a grass texture and a few randomly placed (and nearly identical) trees.

anyway, I don't want to derail this thread with some random screenshot I found on the interwebs, so we'll leave it at that ;)

06 June 2009, 02:14 PM
My advice would be to find a nice photo of a tree, and match that. Then you have some direct reference what it SHOULD look like, instead of just guessing.

06 June 2009, 02:24 AM
There's two things I can point out about the trees that are bothering me.

- Why is there shadows all around the 2nd tree, but no shadows on the actual tree?

- Those type of trees don't grow in that type of environment. Either that, or the trees are too large for that type of landscape. The trunks of the trees arn't large enough to keep a tree that size standing straight up on a slope like that.

06 June 2009, 03:35 AM
Original poster here...

Here's another one I got from the site. BTW. it's from the e-on Vue site and are their showcase images. IMHO, they are truly crappy and, for me, difficult to even look at.

Thare lots of great observations in this thread. I'm not knowledgable enough to comment on them. Any idea what single render feature from a better renderer would drastically improve these two images? Finding this out is the purpose of this thread, so that I can learn.

I would love to discover a book that starts with badly rendered images, points out the bad aspects and then shows how to fix them.

(There's no point in discussing the Vue product. I just happened to use theirs as examples of not-believable)

06 June 2009, 08:11 PM
Remember that the human eye is conditioned to look for the brightest and the most contrasty thing in an image. When you "glance at" a picture, this is what determines what "will draw your eye." And usually, this is what makes a picture "look wrong."

Each of these images were composited from sources that were not designed to go together. They have elements of equal sharpness and brightness which, as such, the eye attempts to assimilate at one time ... and they clash. Badly.

In the second image, for example, we've got foreground and background clamoring for attention, and the background looks like foreground because, in the picture from whence it came, it probably was. The lens f-stops were probably not the same. The lighting was that of "a foreground object." And you discover quickly that you can't get away with such things... not if the image is going to be subjected to close inspection, that is.

(If it won't, then "you can get away with Q-Tips," as George Lucas in fact did on the first theatrical release of Star Wars Episode One. A brief crowd-shot in the podracer sequence was "faked" using a box of colored Q-tips. A waterfall was made of salt. It worked... at least long enough to get the movie out the door on time.)

06 June 2009, 02:34 PM
It's all in the lighting for me. First of all, tint your lights just a little bit green. If you've ever been in a forest, you see the light, due to reflection and all, is just a tad greenish.

Secondly, creating shape in 3D is all in shadows and highlights. Have you ever noticed that very very few people make images that occur at high noon? That's because the lighting is too even, very few shadows and highlights to model the 3D shape. You need your light at an angle so you have a shadow side and a light side. I could mention bounce lights and rim lights and all that jazz, which also applies, but you may not be at a level, or working with software that really can take advantage of that.

I don't know what's possible in Vue, never used it. But you might also add just a wee bit of purple to your shadows. This is traditional art technique which seems to work really well. Not so much purple that the shadows are obviously purple, just enough to slightly bend them in that direction. For some reason this emulates real world shadows more closely.

06 June 2009, 02:50 PM
Good suggestions. Looking back at the first image, I'm thinking the execution of the leaves looks kinda like a wet-on-wet painting by Bob Ross. Not that there's anything wrong with that
but it's like stippling heavy green oil paint in with the end of the bristles of a stiff big round brush. I think also that the ground treatment is off in some way... maybe I'm expecting some higher vegetation like meadow grass. There are not enough contrasts in general.
It's interesting to stare at something like this, knowing something is off really badly, but you can't put your finger on on any one thing and say that's the biggest culprit. It's instructive.

Looking at the second image, the big offender s are the rocks and water. Neither are realistic enough, due in part to neither element borrows colour from the other. It's like they were cut out of two different photos and pasted up. The water is real bad. Hard to even look at.

06 June 2009, 03:01 PM
"I think also that the ground treatment is off in some way... maybe I'm expecting some higher vegetation like meadow grass."

That's one of the problems I find in many Vue renders. Now mind you, I think Vue is quite a nice program, but many renders I've seen have this problem, Groundcover is too uniform in height and too evenly distributed. I don't know if it's possible in Vue to use height maps to control varying height of grass, and use a distribution map to control grass density and such. A forest ground should have varying heights of foliage, weeds, different grasses, spots of bare ground, rocks, twigs, etc. Quite a lot of detail, i know, but a forest is essentially chaotic and should never look nicely manicured.

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