From BlenderWiki

[edit] Introduction

We are going to practice lighting, and to make it more interesting we will use the same scene (same objects and materials) and only change the lights. You can use the provided .blend file in which Cornelius has been caught practicing "to render or not to render" with a Suzanne head he just found laying around on the floor with some other primitive objects. Additionally, we can only see two rather white walls forming a corner behind him. Everything else will be created with lights.

You can look at the exact values in the .blend files, this text is the explanation so you invest the time reasoning and experimenting, then later you can create your own scenes with the ideas you should had learnt here. Each scene uses the first layers to group objects to make the light effects work correctly, or separate cases ("variations").

• Base file
• Sunny scene
• Cloudy scene
• Overcast scene
• Night scenes
• Flashlight scene
• Room scenes
• for diffuse map
• for bump map

For those wondering why no 3 point light exercise the reasons are two: there is one already in the Manual and it is a studio setup that gets boring fast, you will only see it in TV news and similar things. In the next exercises we are going for what looks fine, not for a "by the book" solution. Good photographers avoid it, as it has been abused a lot, and thus hard to get any striking image with it.

[edit] Sunny

Let's start with typical scene, sunny day, around noon. Before launching Blender, stop and think what does a typical sunny day infer: strong Sun, nearly perpendicular to the ground, and a rather white looking image. Those parts not lit by the Sun will be illuminated by the light scattered by the clear blue sky and surrounding objects.

First we add an Hemi light called Sun Hemi, in slightly yellowish shade and with Energy above default. We disable specular in it by clicking NoSpecular, as we will add this later with another light. This is a trick you can resort to often, so you can control specular separate from diffuse. In some other cases, like all the secondary lamps, not having specular and / or shadows is a great help; you add extra light to fix things, but do not create clues that betray that light.

For specular we create Sun Spec, of Sun type. It has NoDiffuse enabled, logically. Shadows in this case are not computed at all, which is a pity, as we would benefit from the shadow operation being used to mask off specular highlights in those places that do not get direct light.

So we add a lamp exclusively for shadows, Sun Shadows. The Energy is different, but it is also of Sun type, so shadow is created by parallel rays. Now it is starting to look sunny, with a strong shadow under just about everything.

Time for the first light that simulates indirect light, that from the sky. With a simple name like Sky Bounce, a blueish shade and reduced Energy, we point it a bit up and to the right, opposed to the sun ones (not perfectly, we just want a good look, simple as that). This way, the back side of things gets a bit of light, as if the floor, walls and sky itself in general bounced part of the Sun light. Indeed, it is starting to get sunny.

Howeverm we need the Extra Punch, to make things really look like they are under a strong summer Sun at the middle of the day. So we add that light, without specular and placed over the things we need to light up. It is perfect now... or near perfect.

To achieve a better result, we are going to fix the background. As I have mentioned, if something looks bad, we just add a local fix, like real photographers do with their reflectors and flashes. However, unlike them, we have a lot more control, we can get lights that do not cast shadows, cause only diffuse or specular lighting, affect a limited number of objects or even the weirdest things: are negative. We have a problem with the top of the head and the back wall, they lack constrast as they are pretty much the same shade. Adding a negative light that affects only the walls by placing them on the same layer and making it of limited range with Sphere gives us the difference.

[edit] Cloudy

Now think about a sky with some sparse clouds but big and thick enough to cast shadows, but still with some breaks which allow the Sun to reach the ground directly at some instance in time.

For this case we start with Sky Direct, a Hemi light so it gives a spread light, enabling NoSpecular so that it does not cause any shininess. It is pointed with the angle we would assume the sun would have. See the image and notice how it starts to define what we are looking for, but looks poor.

To match it we create Sky Bounce, another Hemi without specular. We assign a slight greenish colour to match the floor tiles and lower the Energy. The direction is approximately the opposite than Sky Direct. We can see how the extreme dark areas become a bit lighter, and the wall changes shade slightly, but what is more important, we give the impression that the tiles bounce a bit of light.

Lets move to the main light Sun Shadow, a Spot for quick soft shadows. The position is above and to the right, so we can point it more or less like the Sky Direct. We adjust the ClipEnd and ClipSta to only cover the space with objects. The Energy is raised noticeably and the colour slightly tinted to yellow by decreasing blue, so it gives the idea of strong sun that passes through the clouds. ShadowBufferSize is increased, as we are going to also to increase Samples and Soft. Bias is lower than default since while performing test renders, it created artifacts.

As you will notice, there are some extra shadows in the image, that is due the texture Sun Shadow (yes, it matches the lamp name), a basic Clouds procedural texture with contrast increased and repositioned via the Texture and Input panel in F5. It is cloudy, so we need shadows from them, but also places where the Sun passes through the clouds. We could use Object instead of View, and then animate the clouds moving as if they were being blown about in the wind.

Final touch, we need to create a stronger shadow near the contact with the ground, as the light scattered by the clouds will work as huge but low intensity extra source. So time to add one or more spots (three duplicated in this image), placed above or slightly moved towards the Sun so they do not appear out of place by opposing the main origin of light. We only want the extra shadow so click OnlyShadow, and want a soft effect, so raise Soft and also Samples to avoid artifacts.

[edit] Overcast

Next is a fully covered sky, probably rainy. As we are not going to touch the objects or materials, we will assume just before it begins raining, and so everything is still dry, no need of adjusting materials to make them look wet or modeling small puddles.

The main principle is that the sun will hit the clouds, and they will scatter the light, so basically we have a huge smooth source above us. So to start, create a Hemi lamp, Sky Main. It points just to the ground, as we are talking about the entire sky hemisphere being full of grey clouds. We do not want specular from this lamp, look at any overcast photo, no clear highlights.

As you may have already guessed, we want to make this light bounce off of our ceramic based floor, so add a greenish Hemi, Tile Bounce. It is low energy, of course, and NoSpecular. Extreme dark parts are less so now.

The wall is looking rather dark for my taste, it is supposed to be white paint, and even in a fully covered sky, it should not look so dark. The solution is easy, add Wall Fix, an Hemi light without specular, Energy slightly lowered (it required some test renders until a good value was achieved) and pointing at the corner. We copy the 'Walls and Ground in a new layer with this lamp, press M then Shift LMB the layer where you want the objects to reside also. The other objects will keep the light we had already achieved, but the walls and ground will be a bit lighter.

Let's go for the final part, the soft shadows. Some would just use Ambient Occlusion, but we are going to use a derivation from the basic multi spot method. We will add an UVSphere named Sky System, with 15 divisions in U and V, and later remove all of the bottom part except the top 4 rings of vertices and the topmost vertex, in total we keep 61 vertices. Remember to calculate normals inside with Shift Ctrl N. Then scale it big, say 10 times and move it above our scene.

For the lamp, we create Sky Shadows, a Spot of really low Energy 0.04, but increased Soft and ShadowBufferSize. We only want the shadow, not other contributions so enable ShadowOnly. If you multiply 61 * 0.04 you get 2.44 which can be a bit high, but taking into account that the spots will not point to the same place, it will look ok. Once you have the lamp, parent it to the partial sphere.

We could leave this image as is, but the foot which is furthest away looks a bit too dark compared to the rest. A photographer could try some kind of reflector or using flash, but in this tiny place it could do more harm than anything, as a real reflector or flash will also cause real highlights and shadows.

I mention all of this to show again how sometimes the simplification of Blender works for us and compensates for all the extra lights we have to setup so we fake the real bouncing. We light up the problematic part with a Spot named Foot Fix. We increase SpotBi to the maximum so the light has a really soft progression, disable shadows and specular, and render until we are happy with the right Energy. Finally, that is all, our monkey in a stormy day.

[edit] Night

Here we will reproduce a night environment, but with a bit of artistic freedom in same manner as that used in films. If you look at real night, you will see... you will hardly see. In movies the nights are a bit more lighted due two reasons. The first reason is being able to communicate with the viewers, provide a bit more information than what would exist in reality so that they do not become bored, miss details and just wonder what is going on in that near black rectangle. The other reason is that in some cases the filming is performed with lights due to time constraints or camera limitations, and by means of processing to make the image look darker and with less contrast, achieve a night time look.

So let's start with the plain night look, and for that an Hemi named Sky Hemi. Night sky works as a huge source of low intensity due to the light being scattered in the atmosphere. The intensity is rather low and the colour we use is blue. Again, to avoid shininess, we disable specular. The orientation of this light towards the the corner of the terrace, even if the sky is above, so we make better use of the low intensity (a first small artistic license).

Next is a bounce light, Sky Bounce, which we point directly up to get some definiton of the objects' edges. We keep it blue, since logically it should be black, as the blue light would be absorbed by the green tiles. Let's break the rules a bit and attribute the effect to the white walls.

Time to add a shadow effect, that we could even point to be of a small moon. For this we use Sky Shadows Spot light, set to only shadows and rather smooth. The colour is slightly cyanish, to mix the effect of the blue sky and the pure light of the Sun that the Moon reflects. The smooth controls is set a bit high. As result of all these adjustments, we see that the image looks pretty nightlish, dark and with some acceptable issues in order to pick up details, just like in real life, but we can still see what is going on.

[edit] Variation 1: Movie Full Moon

We could add a more film style Moon, or full moon with no clouds and clear atmosphere, even if we have just shown there were some clouds. So we will use a slightly stronger source. With a simple Sun type lamp with raytraced shadows, we get such an effect, for example.

[edit] Variation 2: House Light

This is a typical trick in films, adding more lights so other parts of things are also lighted, for extra definition. Take a detective in a dark room, looking at the street through the blinds. In real life, the back of his head will be hardly lighted by just a bit of the light bounced by the room. In films you will see there is a bit more light, and the best way is to find a plausible excuse, like a small desk lamp or the light of the corridor that filters through a frosted glass door. The extra light gives definition and also dramatic expression, so we are going to do a similar thing, and open a door into our terrace.

For this task we just add a square spot and avoid having to add a texture. This Open Door light gets buffer based shadows for a quick result, soft edges and an orangish colour for the incandescent bulb look. We also enable Quad and Sphere to get a realistic fall off.

[edit] Flashlight

What if instead of thinking Cornelius is standing in some kind of tiled backyard or terrace, we find him in the cellar, while we were looking for the electricity's main switch? We carry our own flashlight, and the damn monkey keeps on practicing theatre as if nothing happened... oh well.

First we place a Spot light near the camera, a bit to the side and pointing forward and with a yellowish colour. The main idea of this Flashlight is to have a really smooth transition to the edges with a bright center and soft outer part, so maximize SpotBi.

It is our only source, so raise the Energy to 2.0, the concentration will make this high value look fine, as it will only be used near the center of the beam. What is more, for this kind of small sources, compared to suns or skies, enabling Quad and Sphere makes a lot of sense, as it provides a realistic progression, the further away, the bigger the area the photons have to cover... or viewed in another way, less photons per unit area. We can raise Soft if we want fuzzier shadows, but default is fine.

For mood, we enable Halo, and keep halo Step at a good value, like 4. This way the room looks a bit dusty and parts that looked black now look a bit better.

If you take a flashlight you will notice the light is not even, probably casts some kind of ring pattern and has strange spots; all due to the imperfections and dust in the bulb, reflector and glass. So we will add one or more textures to the spot. We could paint our own texture or build it with procedurals. First the Flashlight Rings, which we can get via Wood Noise Rings, by making them not so random.

And with a Clouds procedural texture, we can get the noise of Flashlight Dirt. The difference is rather small, but enough to make the texture look imperfect and thus real.

There is something missing, the bounced light. After all, we are pointing a flashlight towards a white wall and green tiled floor. Adding Wall Bounce, a yellowish Hemi light of low intensity we light up the ground a bit, and what is more important, we define the edges of all the objects, specially the blue cone and the right hand that were hardly visible are now visible in contrast with the background, even if just slightly.

The Flashlight also points to the ground, so we will make our ceramic ground bounce a bit of light too, in this case a yellow green shade. By pointing it up we not only follow the logical direction, but also define the shapes a bit more, a bit of the light added on them or in the background walls, and thus improves the contrast.

[edit] Room

For this case, we will assume we have a window on the right side, the late evening sun is entering through it, so we have powered on the ceiling light fixture that holds five energy saving lamps (those electronic spiral shaped flourescent tubes packed as bulbs).

The first lamp we add is a late evening Sun, with a texture to make the window a bit more interesting.

Then we add a pentagon and parent a blueish light which we call Energy Saving to it. This light will have raytraced shadows and sphere range to limit them. The Energy is set to 0.8, but as they they fade with distance even 5 lights will not look too bright. We do not care if the shadows look a bit strange, as that is the way they look, just go to a room with multiple bulbs placed together and examine the shadows they cast, they create complex patterns.

Next, we start with the bounces, for example Tile Bounce. This is a green looking Hemi, to take into account the interior lights and the ground shade.

Other bounce is the walls, clearly the far away wall will bounce back some light, so we add Wall Bounce lamp. The other wall will not bounce much of the fluorescent as it is placed perpendicular to the location of the ceiling lamps.

Well, by the position of the light, we can assume some light will bounce from the right to the left, due to another wall there (if there is a window, there must be a wall holding it, and we are not getting more light from windows, so indeed the wall will be enough to contribute), so we add Wall Bounce 2.

It still looks a bit weird, the wall corner has too strong of a shadow. Maybe we should add Extra Punch and try to fix that.

[edit] Variation: No Window

Ok, the open window idea does not work very nice, since the shadows become confusing rather quickly. However, the ceiling lights give a good look for an interior environment with fluorescent lamps that everyone can grasp. So disable the external light.

[edit] Conclusions

So, what we have learnt? That light can change a scene rather drastically, without even the slightest of modifications to any material. Another important detail is thinking what we want in advance and then imagine how real light will behave so we can use the proper tricks. Finally, no matter if it should be right based in the values we use, we have to get it too look right, even if that means forcing things, doing nasty cheats to cover issues and taking adventage of our errors if they look fine anyway; or maybe rethinking the original plan a bit. It is not what should be correct, but what looks correct.

You can find more info at sites like Kodak photography tips, Itchy Animation light tutorial or even some video tutorials about photography lighting