Lighting is a sorely overlooked issue in too many 3D renders. You can have the most highly detailed models and textures you like but without convincing lighting it'll still just look like lego bricks. Following is an example of how I light my models. I've tried to keep it simple so that it can be used with any 3D renderer (provided that renderer can use shadow maps) and so that you don't have to be a rocket scientist or have fancy radiosity plugins to render a realistic looking rocket.
As this is a generic tutorial, I cannot give specific instructions so it may require you to read up on lights and shadow maps in your respective modelling/rendering packages before you can put it into practice.
First of all, forget ray-tracing. It's waaaaay too accurate. I use raytracing for mirror reflections and nothing else. It casts nice, razor sharp shadows, which I find unconvincing. Due to the diameter of the sun, shadows should have a very slightly blurred edge, becoming more diffused as the shadows moves further away from the subject.
To be fair, the following effect can be achieved with raytraced shadows but you'll need a heck of a lot of lights which slows down render times considerably. I prefer to use Shadow maps. You might need to use very high res maps for sun shadows which eats up memory and slows down render time but not much more - if any - slower than raytraced shadows and they give you more control over the sharpness of the shadow.
Okay, first up is an example of an object with just a main light and no shadows atall.
This is obviously completely unconvincing. There's no indication of where the sphere connects with the cube or where the cube connects with the floor. It could be floating in space.
So, we need to turn the shadow on. In this next image we can see the same light casting a ray-traced shadow. Note that it is a low pass so it is aliased, giving edges that stepped look. That can be fixed, but also notice how sharp the shadow edge is. That cannot be altered with Ray-Traced shadows.
In the next picture we can see the same light casting a fairly high res shadow map (1024). Notice how it's edges are blurred. Maybe a might too blurred. That also can be altered by raising the resolution of the shadow map to make it sharper or lowering the resolution to make it more blurred (for overcast shadows for example).
The main thing I want to draw your attention to in this image however is the fact that the shadows are completely, solid black. That's fairly realistic if you're rendering a space scene, but no use to man nor beast if you're doing a land-based scene or indeed if you want to show off your hard work in all it's finery.
Okay, you can turn up the ambient light, if it's not on allready. Well, I wouldn't because you get this:
The problem with ambient light is that it doesn't cast shadows. What that means is that all it does is lighten the existing shadows. In effect it makes objects glow. You need to shut off that ambient light. Shut it off and never cast eyes upon it again.
What I do is set up an array, a sphere in effect of dim lights all around the object like this:
Left is the front view and right is the top.
There is a ring above the object pointing towards it. There is a ring just above the horizon and pointing down and finally a ring under the object pointing up.
These lights are known as 'fill-lights' and would be set to around .3 of full intensity and they would cast very low res shadow maps (128). These maps would also be quite blurred. Most shadow maps have the ability to increase their filtering, which makes them more blurred. This has the effect of highlighting exposed surfaces and creating very soft shadows that gradually intensify as the geometry dissapears into a recess. This creates a much more realistic ambient light that gives intersections on objects a more visual connection. Note how it gets darker as the sphere meets the cube. Also the cube is darker around it's base where it meets the floor:
As this is a generic tutorial, I cannot give specific instructions so it may require you to read up on lights and shadow maps in your respective modelling/rendering packages before you can put it into practice.
First of all, forget ray-tracing. It's waaaaay too accurate. I use raytracing for mirror reflections and nothing else. It casts nice, razor sharp shadows, which I find unconvincing. Due to the diameter of the sun, shadows should have a very slightly blurred edge, becoming more diffused as the shadows moves further away from the subject.
To be fair, the following effect can be achieved with raytraced shadows but you'll need a heck of a lot of lights which slows down render times considerably. I prefer to use Shadow maps. You might need to use very high res maps for sun shadows which eats up memory and slows down render time but not much more - if any - slower than raytraced shadows and they give you more control over the sharpness of the shadow.
Okay, first up is an example of an object with just a main light and no shadows atall.
This is obviously completely unconvincing. There's no indication of where the sphere connects with the cube or where the cube connects with the floor. It could be floating in space.
So, we need to turn the shadow on. In this next image we can see the same light casting a ray-traced shadow. Note that it is a low pass so it is aliased, giving edges that stepped look. That can be fixed, but also notice how sharp the shadow edge is. That cannot be altered with Ray-Traced shadows.
In the next picture we can see the same light casting a fairly high res shadow map (1024). Notice how it's edges are blurred. Maybe a might too blurred. That also can be altered by raising the resolution of the shadow map to make it sharper or lowering the resolution to make it more blurred (for overcast shadows for example).
The main thing I want to draw your attention to in this image however is the fact that the shadows are completely, solid black. That's fairly realistic if you're rendering a space scene, but no use to man nor beast if you're doing a land-based scene or indeed if you want to show off your hard work in all it's finery.
Okay, you can turn up the ambient light, if it's not on allready. Well, I wouldn't because you get this:
The problem with ambient light is that it doesn't cast shadows. What that means is that all it does is lighten the existing shadows. In effect it makes objects glow. You need to shut off that ambient light. Shut it off and never cast eyes upon it again.
What I do is set up an array, a sphere in effect of dim lights all around the object like this:
Left is the front view and right is the top.
There is a ring above the object pointing towards it. There is a ring just above the horizon and pointing down and finally a ring under the object pointing up.
These lights are known as 'fill-lights' and would be set to around .3 of full intensity and they would cast very low res shadow maps (128). These maps would also be quite blurred. Most shadow maps have the ability to increase their filtering, which makes them more blurred. This has the effect of highlighting exposed surfaces and creating very soft shadows that gradually intensify as the geometry dissapears into a recess. This creates a much more realistic ambient light that gives intersections on objects a more visual connection. Note how it gets darker as the sphere meets the cube. Also the cube is darker around it's base where it meets the floor:
