I have some camera with perspective projection and object in the (0,0,0).
I computed "bounding frame"(size in pixels on screen) of this object according to this camera and scaled it to fit the screen size. And now it in the middle of screen.
Frame of the scnView is equal to the screen size and I have some UI components above this view(e.g. navigation bar and some big transparent view in the bottom of view). The scnView has some fullscreen background and this object can be scaled/moved/... therefore I need scnview to be fullscreen.
Then I move this object in the middle of "clear area" (the area with absence of UIComponents) and see the bottom of this object (as if it's above me), because my projection is perspective.
I want to move this object in the center of clear area and see like it's in front of me without any distortion. How can I achieve that?
I see 2 solutions.
1) Draw my object offscreen in texture and after that draw this texture on screen in required position.
2) create scnView a bit taller. For example set frame size to = (0, (bottomHeight - topHeight) / 2, width, height + (bottomHeight - topHeight) / 2) to move the center of scnView in required position.
But I don't like first solution due to addition draw call and second solution even sounds crappy.
P.S. sorry for that pictures
Update: Basically I want to use perspective projection and move 3D object like a 2D image in SceneKit.
Sorry if I'm not be understanding correctly, but can you strafe camera up and center it, or will that not be clear enough?
func strafeY(vAmount: XFloat)
{
nPosition = cgVecAdd(v1: nPosition, v2: cgVecScalarMult(v: nTarget, s: vAmount))
}
Try this... generate a new scenekit game project, then replace the default rotation with the code below.
Rotate X slightly as you move the object up to to "somewhat" maintain the relationship to the eye.
You could create a similar but separate routine to do smaller increments to smooth it out.
ship.runAction(SCNAction.rotateBy(x: CGFloat(GLKMathDegreesToRadians(-90)), y: 0, z: 0, duration: 0))
let vRotateAmount: Float = 3
let vAction1 = SCNAction.move(to: SCNVector3Make(0, 1, 0), duration: 1)
let vAction1a = SCNAction.rotateBy(x: CGFloat(GLKMathDegreesToRadians(vRotateAmount)), y:0, z:0, duration: 1)
let vAction2 = SCNAction.move(to: SCNVector3Make(0, 2, 0), duration: 1)
let vAction2a = SCNAction.rotateBy(x: CGFloat(GLKMathDegreesToRadians(vRotateAmount)), y:0, z:0, duration: 1)
let vAction3 = SCNAction.move(to: SCNVector3Make(0, 1, 0), duration: 1)
let vAction3a = SCNAction.rotateBy(x: CGFloat(GLKMathDegreesToRadians(-vRotateAmount)), y:0, z:0, duration: 1)
let vAction4 = SCNAction.move(to: SCNVector3Make(0, 0, 0), duration: 1)
let vAction4a = SCNAction.rotateBy(x: CGFloat(GLKMathDegreesToRadians(-vRotateAmount)), y:0, z:0, duration: 1)
let seq = SCNAction.sequence([vAction1, vAction1a, vAction2, vAction2a, vAction3, vAction3a, vAction4, vAction4a])
let allSeq = SCNAction.repeatForever(seq)
ship.runAction(allSeq)
Solved it by changing camera projectionTransform. Smth like:
let newMatrix = SCNMatrix4Mult(initialProjectionCameraMatrix, translationMatrix)
Related
I have a SceneKit scene in which the camera is stationary, and is positioned like this: cameraNode.position = SCNVector3(0.0, 0.0, 100.0). Other than that, the camera has the default configuration.
In the scene is a single, spherical SCNNode with a physics body.
Below the sphere is a flat plane, with a physics body, on which the sphere rolls around. The plane is positioned in the center of the scene, at SCNVector3(0.0, 0.0, 0.0).
What I need is for the scene to be surrounded by invisible "walls" that are positioned exactly at the edges of the screen. The sphere should bounce off these static physics bodies so it never leaves the screen.
I've tried placing one of these "walls" (an SCNNode with an SCNBox geometry) using the actual screen dimensions, but the positioning is incorrect; the node is apparently off screen. This is presumably because SceneKit coordinates are in meters, not pixels or whatever.
Question: How can I figure out the positioning of the "walls" so that they are fixed to the edges of the screen?
Thanks for your help!
Use the SCNSceneRenderer's unprojectPoint(_:) method to convert left and right edges of the screen to 3D space coordinates and add two planes in those coordinates.
let leftPoint = SCNVector3(scnView.bounds.minX, scnView.bounds.midY, 1.0)
let righPoint = SCNVector3(scnView.bounds.maxX, scnView.bounds.midY, 1.0)
let leftPointCoords = scnView.unprojectPoint(leftPoint)
let rightPointCoords = scnView.unprojectPoint(righPoint)
let rightPlane = SCNPlane(width: 100.0, height: 100.0)
let leftPlane = SCNPlane(width: 100.0, height: 100.0)
let rightPlaneNode = SCNNode(geometry: rightPlane)
rightPlaneNode.eulerAngles = .init([0.0, .pi / 2, 0.0])
rightPlaneNode.physicsBody = .init(type: .static, shape: nil)
let leftPlaneNode = SCNNode(geometry: leftPlane)
leftPlaneNode.physicsBody = .init(type: .static, shape: nil)
leftPlaneNode.eulerAngles = .init([0.0, .pi / 2, 0.0])
rightPlaneNode.position = rightPointCoords
leftPlaneNode.position = leftPointCoords
scene.rootNode.addChildNode(rightPlaneNode)
So, obviously there's a mathematical solution to this problem, and that's the best way to do this. Unfortunately, I'm not very good at math, so I had to come up with another solution.
First, I create the wall to be located at the top edge of the screen. It will begin at the center of the scene:
let topEdge = SCNNode()
let topEdgeGeo = SCNBox(width: MainData.screenWidth, height: 5.0, length: 5.0, chamferRadius: 0.0)
topEdge.geometry = topEdgeGeo
topEdge.physicsBody = SCNPhysicsBody(type: SCNPhysicsBodyType.kinematic, shape: SCNPhysicsShape.init(node: topEdge))
topEdge.physicsBody?.categoryBitMask = CollisionTypes.kinematicObjects.rawValue
topEdge.physicsBody?.collisionBitMask = CollisionTypes.dynamicObjects.rawValue
topEdge.physicsBody?.isAffectedByGravity = false
topEdge.physicsBody?.allowsResting = true
topEdge.physicsBody?.friction = 0.0
topEdge.position = SCNVector3(0.0, 0.0, 2.5)
scnView.scene?.rootNode.addChildNode(topEdge)
I then repeatedly reposition the wall a little bit farther up the y axis until it's no longer within the camera's viewport:
var topWallIsOnScreen: Bool = scnView.isNode(topEdge, insideFrustumOf: scnView.pointOfView!)
while topWallIsOnScreen {
topEdge.position.y += 0.001
topWallIsOnScreen = scnView.isNode(topEdge, insideFrustumOf: scnView.pointOfView!)
}
The end result is that the wall is positioned at the top edge of the screen. I was concerned about performance, but it seems to work just fine.
I am currently making a Sprite and I want it to animate before it disappears.
For example: I want it to animate it in the sense that it disappears from the top of the block until the bottom. To put it another way, I want to the size to decrease slowly until there is nothing left. But I want to give it the appearance that it is disappearing rather than scaling to nothing.
let hand = SKSpriteNode(imageNamed: "hand")
hand.size = CGSize(width: size.width/10, height: size.height/30)
hand.position = CGPoint(x: CGFloat(posX-2)*size.width/10+offsetX, y:CGFloat(posY)*size.height/30+offsetY)
addChild(hand)
tl;dr is it possible to make this sort of effect using SpriteKit in Swift.
Ideal Animation: https://ibb.co/sPsffmK
SKAction is an animation that is executed by a node in the scene. Actions are used to change a node in some way (like move its position over time), but you can also use actions to change the scene, like doing a fadeout.
In your case, you can apply multiple animations:
let move_action = SKAction.moveBy(x: -100, y: 0, duration: 1.0)
let scale_action = SKAction.scale(to: 0.0, duration: 1.0)
let fade_action = SKAction.fadeAlpha(to: 0.0, duration: 1.0)
hand.run(move_action)
hand.run(scale_action)
//hand.run(fade_action)
In the previous example, the hand runs the move and scale animation at the same time. But you can also make the hand to move to the position, and after it reaches, to scale it.
let sequence = SKAction.sequence([move_animation,scale_animation])
hand.run(sequence)
There are lots of animations that SKAction has, here you can find the complete list.
I am very new to SceneKit and your help will be really appreciated!
I have a 200x200 sized SCNView in my UIView, which is at the centre of super view.
I want to put a SCNCylinder inside, such that the SCNCylinder covers full SCNView. I read that all these views of Scenekit are defined in meters, so how do I form a relationship between the dimensions of my screen and the
SCNCylinder.
I tried:
var coinNode = SCNNode()
let coinGeometry = SCNCylinder(radius: 100, height: 2)
coinNode = SCNNode(geometry: coinGeometry)
coinNode.position = SCNVector3Make(0, 0, 0)
coinScene.rootNode.addChildNode(coinNode)
let rotate90AboutZ = SCNAction.rotateByX(-CGFloat(M_PI_2), y: 0.0, z: CGFloat(M_PI_2), duration: 0.0)
coinNode.runAction(rotate90AboutZ)
ibOutletScene.scene = coinScene
But this leaves a margin between my coinScene and the ibOutletScene. How do I remove this space?
I also tried adding Camera:
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3Make(0, 0, 100)
coinScene.rootNode.addChildNode(cameraNode)
But I see random behaviour with this and the coinNode gets hidden! How should I position my camera? Or is there any other way to remove extra space from my ibOutletScene?
Edit:
This is how it looks if I don't add camera. There is a margin between red scene and green coin. I tried multiple sizes for the coin, but I am unable to remove this margin unless I add a camera. But, If I add camera, I get another problem, mentioned below this screenshot.
If I don't add the camera, The rotation animation on coin works perfectly, but If I add camera,the rotation enlarges the and then becomes small again with the animation. How can I rotate it on its axis, without increasing the size?
I am using following code to rotate the coin:
The same code works fine without camera, but enlarges the coin after adding camera. Checkout the snapshot.
let rotate = SCNAction.rotateByX(0, y: -2 * CGFloat(M_PI_2), z: 0, duration: 2)
coinNode.runAction(rotate)
The random behavior might be caused by the last line in your first code snippet. You're starting an animation, and then adding the scene to the view.
Instead, build your scene, attach it to the view, and then start your animation. Setting a non-zero duration for the action will give you a more pleasing transition.
As for the extra space, it would help us understand if you post a screenshot. But you're going to have to do a bit of trigonometry.
It looks like you have a scene that you want to be blocked by a coin, that then rotates out of the way? Simulate that yourself with real objects. Put your eye down at the edge of your desk. Put a coin out a ways from your eye. How far does that coin have to be in order to block particular objects farther away on your desk?
In SceneKit, you can query the field of view of the SCNCamera. You know the size of your coin and the size of the view. Calculate the distance from the camera needed for the projected diameter of your coin to equal the width of your view. Put the coin there.
I have created a big circle with a UIBezierPath and turned it into a Sprite using this,
let path = UIBezierPath(arcCenter: CGPoint(x: 0, y: 0), radius: CGFloat(226), startAngle: 0.0, endAngle: CGFloat(M_PI * 2), clockwise: false)
// create a shape from the path and customize it
let shape = SKShapeNode(path: path.cgPath)
shape.lineWidth = 20
shape.position = center
shape.strokeColor = UIColor(red:0.98, green:0.99, blue:0.99, alpha:1.00)
let trackViewTexture = self.view!.texture(from: shape, crop: outerPath.bounds)
let trackViewSprite = SKSpriteNode(texture: trackViewTexture)
trackViewSprite.physicsBody = SKPhysicsBody(edgeChainFrom: innerPath.cgPath)
self.addChild(trackViewSprite)
It works fine. It creates the circle perfectly. But I need to resize it using
SKAction.resize(byWidth: -43, height: -43, duration: 0.3)
Which will make it a bit smaller. But, when it resizes the 20 line width I set now is very small because of the aspect fill. So when I shink it looks something like this:
But I need it to shrink like this-- keeping the 20 line width:
How would I do this?
Don't know if this would affect anything, but the sprites are rotating with an SKAction forever
-- EDIT --
Now, how do I use this method to scale to a specific size? Like turn 226x226 to 183x183?
Since by scaling down the circle, not only its radius gets scaled but its line's width too, you need to set a new lineWidth proportional with the scale. For example, when scaling the circle down by 2, you will need to double the lineWidth.
This can be done in two ways:
Setting the lineWidth in the completion block of the run(SKAction, completion: #escaping () -> Void) method. However this will result in seeing the line shrinking while the animation is running, then jumping to its new width once the animation finishes. If your animation is short, this may not be easy to observe tough.
Running a parallel animation together with the scaling one, which constantly adjusts the lineWidth. For this, you can use SKAction's customAction method.
Here is an example for your case:
let scale = CGFloat(0.5)
let finalLineWidth = initialLineWidth / scale
let animationDuration = 1.0
let scaleAction = SKAction.scale(by: scale, duration: animationDuration)
let lineWidthAction = SKAction.customAction(withDuration: animationDuration) { (shapeNode, time) in
if let shape = shapeNode as? SKShapeNode {
let progress = time / CGFloat(animationDuration)
shape.lineWidth = initialLineWidth + progress * (finalLineWidth - initialLineWidth)
}
}
let group = SKAction.group([scaleAction, lineWidthAction])
shape.run(group)
In this example, your shape will be scaled by 0.5, therefore in case of an initial line width of 10, the final width will be 20. First we create a scaleAction with a specified duration, then a custom action which will update the line's width every time its actionBlock is called, by using the progress of the animation to make the line's width look like it's not changing. At the end we group the two actions so they will run in parallel once you call run.
As a hint, you don't need to use Bezier paths to create circles, there is a init(circleOfRadius: CGFloat) initializer for SKShapeNode which creates a circle for you.
The code below is used to create a scene and create blocks in SceneKit. The blocks come out looking flat and not "3D enough" according to our users. Screenshots 1-2 show our app.
Screenshots 3-5 show what users expect the blocks to look like, that is more 3D-like.
After speaking to different people, there are different opinions about how to render blocks that look more like screenshots 3-5. Some people say use ambient occlusion, others say voxel lighting, some say use spot lighting and use shadows, or directional lighting.
We previously tried adding omni lighting, but that didn't work so it was removed. As you can see in the code, we also experimented with an ambient light node but that also didn't yield the right results.
What is the best way to render our blocks and achieve a comparable look to screenshots 3-5?
Note: we understand the code is not optimized for performance, i.e., that polygons are shown that should not be shown. That is okay. The focus is not on performance but rather on achieving more 3D-like rendering. You can assume some hard limit on nodes, like no more than 1K or 10K in a scene.
Code:
func createScene() {
// Set scene view
let scene = SCNScene()
sceneView.jitteringEnabled = true
sceneView.scene = scene
// Add camera node
sceneView.pointOfView = cameraNode
// Make delegate to capture screenshots
sceneView.delegate = self
// Set ambient lighting
let ambientLightNode = SCNNode()
ambientLightNode.light = SCNLight()
ambientLightNode.light!.type = SCNLightTypeAmbient
ambientLightNode.light!.color = UIColor(white: 0.50, alpha: 1.0)
//scene.rootNode.addChildNode(ambientLightNode)
//sceneView.autoenablesDefaultLighting = true
// Set floor
setFloor()
// Set sky
setSky()
// Set initial position for user node
userNode.position = SCNVector3(x: 0, y: Float(CameraMinY), z: Float(CameraZoom))
// Add user node
scene.rootNode.addChildNode(userNode)
// Add camera to user node
// zNear fixes white triangle bug while zFar fixes white line bug
cameraNode.camera = SCNCamera()
cameraNode.camera!.zNear = Double(0.1)
cameraNode.camera!.zFar = Double(Int.max)
cameraNode.position = SCNVector3(x: 0, y: 0, z: 0) //EB: Add some offset to represent the head
userNode.addChildNode(cameraNode)
}
private func setFloor() {
// Create floor geometry
let floorImage = UIImage(named: "FloorBG")!
let floor = SCNFloor()
floor.reflectionFalloffEnd = 0
floor.reflectivity = 0
floor.firstMaterial!.diffuse.contents = floorImage
floor.firstMaterial!.diffuse.contentsTransform = SCNMatrix4MakeScale(Float(floorImage.size.width)/2, Float(floorImage.size.height)/2, 1)
floor.firstMaterial!.locksAmbientWithDiffuse = true
floor.firstMaterial!.diffuse.wrapS = .Repeat
floor.firstMaterial!.diffuse.wrapT = .Repeat
floor.firstMaterial!.diffuse.mipFilter = .Linear
// Set node & physics
// -- Must set y-position to 0.5 so blocks are flush with floor
floorLayer = SCNNode(geometry: floor)
floorLayer.position.y = -0.5
let floorShape = SCNPhysicsShape(geometry: floor, options: nil)
let floorBody = SCNPhysicsBody(type: .Static, shape: floorShape)
floorLayer.physicsBody = floorBody
floorLayer.physicsBody!.restitution = 1.0
// Add to scene
sceneView.scene!.rootNode.addChildNode(floorLayer)
}
private func setSky() {
// Create sky geometry
let sky = SCNFloor()
sky.reflectionFalloffEnd = 0
sky.reflectivity = 0
sky.firstMaterial!.diffuse.contents = SkyColor
sky.firstMaterial!.doubleSided = true
sky.firstMaterial!.locksAmbientWithDiffuse = true
sky.firstMaterial!.diffuse.wrapS = .Repeat
sky.firstMaterial!.diffuse.wrapT = .Repeat
sky.firstMaterial!.diffuse.mipFilter = .Linear
sky.firstMaterial!.diffuse.contentsTransform = SCNMatrix4MakeScale(Float(2), Float(2), 1);
// Set node & physics
skyLayer = SCNNode(geometry: sky)
let skyShape = SCNPhysicsShape(geometry: sky, options: nil)
let skyBody = SCNPhysicsBody(type: .Static, shape: skyShape)
skyLayer.physicsBody = skyBody
skyLayer.physicsBody!.restitution = 1.0
// Set position
skyLayer.position = SCNVector3(0, SkyPosY, 0)
// Set fog
/*sceneView.scene?.fogEndDistance = 60
sceneView.scene?.fogStartDistance = 50
sceneView.scene?.fogDensityExponent = 1.0
sceneView.scene?.fogColor = SkyColor */
// Add to scene
sceneView.scene!.rootNode.addChildNode(skyLayer)
}
func createBlock(position: SCNVector3, animated: Bool) {
...
// Create box geometry
let box = SCNBox(width: 1.0, height: 1.0, length: 1.0, chamferRadius: 0.0)
box.firstMaterial!.diffuse.contents = curStyle.getContents() // "curStyle.getContents()" either returns UIColor or UIImage
box.firstMaterial!.specular.contents = UIColor.whiteColor()
// Add new block
let newBlock = SCNNode(geometry: box)
newBlock.position = position
blockLayer.addChildNode(newBlock)
}
Screenshots 1-2 (our app):
Screenshots 3-5 (ideal visual representation of blocks):
I still think there's a few easy things you can do that will make a big difference to how your scene is rendered. Apologies for not using your code, this example is something I had lying around.
Right now your scene is only lit by an ambient light.
let aLight = SCNLight()
aLight.type = SCNLightTypeAmbient
aLight.color = UIColor(red: 0.2, green: 0.2, blue: 0.2, alpha: 1.0)
let aLightNode = SCNNode()
aLightNode.light = aLight
scene.rootNode.addChildNode(aLightNode)
If I use only this light in my scene I see the following. Note how all faces are lit the same irrespective of the direction they face. Some games do pull off this aesthetic very well.
The following block of code adds a directional light to this scene. The transformation applied in this light won't be valid for your scene, it's important to orientate the light according to where you want the light coming from.
let dLight = SCNLight()
dLight.type = SCNLightTypeDirectional
dLight.color = UIColor(red: 0.6, green: 0.6, blue: 0.6, alpha: 1.0)
let dLightNode = SCNNode()
dLightNode.light = dLight
var dLightTransform = SCNMatrix4Identity
dLightTransform = SCNMatrix4Rotate(dLightTransform, -90 * Float(M_PI)/180, 1, 0, 0)
dLightTransform = SCNMatrix4Rotate(dLightTransform, 37 * Float(M_PI)/180, 0, 0, 1)
dLightTransform = SCNMatrix4Rotate(dLightTransform, -20 * Float(M_PI)/180, 0, 1, 0)
dLightNode.transform = dLightTransform
scene.rootNode.addChildNode(dLightNode)
Now we have shading on each of the faces based on their angle relative to the direction of the light.
Currently SceneKit only supports shadows if you're using the SCNLightTypeSpot. Using a spotlight means we need to both orientate (as per directional light) and position it. I use this as a replacement for the directional light.
let sLight = SCNLight()
sLight.castsShadow = true
sLight.type = SCNLightTypeSpot
sLight.zNear = 50
sLight.zFar = 120
sLight.spotInnerAngle = 60
sLight.spotOuterAngle = 90
let sLightNode = SCNNode()
sLightNode.light = sLight
var sLightTransform = SCNMatrix4Identity
sLightTransform = SCNMatrix4Rotate(sLightTransform, -90 * Float(M_PI)/180, 1, 0, 0)
sLightTransform = SCNMatrix4Rotate(sLightTransform, 65 * Float(M_PI)/180, 0, 0, 1)
sLightTransform = SCNMatrix4Rotate(sLightTransform, -20 * Float(M_PI)/180, 0, 1, 0)
sLightTransform = SCNMatrix4Translate(sLightTransform, -20, 50, -10)
sLightNode.transform = sLightTransform
scene.rootNode.addChildNode(sLightNode)
In the above code we first tell the spotlight to cast a shadow, by default all nodes in your scene will then cast a shadow (this can be changed). The zNear and zFar settings are also important and must be specified so that the nodes casting shadows are within this range of distance from the light source. Nodes outside this range will not cast a shadow.
After shading/shadows there's a number of other effects you can apply easily. Depth of field effects are available for the camera. Fog is similarly easy to include.
scene.fogColor = UIColor.blackColor()
scene.fogStartDistance = 10
scene.fogEndDistance = 110
scenekitView.backgroundColor = UIColor(red: 0.2, green: 0.2, blue: 0.2, alpha: 1.0)
Update
Turns out you can get shadows from a directional light. Modifying the spotlight code from above by changing its type and setting the orthographicScale. Default value for orthographicScale seems to be 1.0, obviously not suitable for scenes much larger than 1.
let dLight = SCNLight()
dLight.castsShadow = true
dLight.type = SCNLightTypeDirectional
dLight.zNear = 50
dLight.zFar = 120
dLight.orthographicScale = 30
let dLightNode = SCNNode()
dLightNode.light = dLight
var dLightTransform = SCNMatrix4Identity
dLightTransform = SCNMatrix4Rotate(dLightTransform, -90 * Float(M_PI)/180, 1, 0, 0)
dLightTransform = SCNMatrix4Rotate(dLightTransform, 65 * Float(M_PI)/180, 0, 0, 1)
dLightTransform = SCNMatrix4Rotate(dLightTransform, -20 * Float(M_PI)/180, 0, 1, 0)
dLightTransform = SCNMatrix4Translate(dLightTransform, -20, 50, -10)
dLightNode.transform = dLightTransform
scene.rootNode.addChildNode(dLightNode)
Produces the following image.
The scene size is 60x60, so in this case setting the orthographic scale to 30 produces shadows for the objects close to the light. The directional light shadows appear different to the spot light due to the difference in projections (orthographic vs perspective) used when rendering the shadow map.
Ambient occlusion calculations will give you the best results, but is very expensive, particularly in a dynamically changing world, which it looks like this is.
There are several ways to cheat, and get the look of Ambient occlusion.
Here's one:
place transparent, gradient shadow textures on geometry "placards" used to place/present the shadows at the places required. This will involve doing checks of geometry around the new block before determining what placards to place, with which desired texture for the shadowing. But this can be made to look VERY good, at a very low cost in terms of polygons, draw calls and filtrate. It's probably the cheapest way to do this, and have it look good/great, and can only really be done (with a good look) in a world of blocks. A more organic world rules this technique out. Please excuse the pun.
Or, another, similar: Place additional textures onto/into objects that have the shadow, and blend this with the other textures/materials in the object. This will be a bit fiddly, and I'm not an expert on the powers of materials in Scene Kit, so can't say for sure this is possible and/or easy in it.
Or: Use a blend of textures with a vertex shader that's adding a shadow from the edges that touch or otherwise need/desire a shadow based on your ascertaining what and where you want shadows and to what extent. Will still need the placards trick on the floors/walls unless you add more vertices inside flat surfaces for the purpose of vertex shading for shadows.
Here's something I did for a friend's CD cover... shows the power of shadows. It's orthographic, not true 3D perspective, but the shadows give the impression of depths and create the illusions of space:
all answers above (or below) seem to be good ones (at the time of this writing) however,
what I use (just for setting up a simple scene) is one ambient light (lights everything in all directions) to make things visible.And then one omnidirectional light positioned somewhere in the middle of your scene, the omni light can be raised up (Y up I mean) to light the whole of your scene. The omni light gives the user a sense of shading and the ambient light makes it more like a sun light.
for example:
Imagine sitting in a living room (like I am right now) and the sun-light peers through the window to your right.
You can obviously see a shadow of an area that the couch is not getting sun light, however you can still see details of what is in the shadow.
Now! all the sudden your wold gets rid of ambient light BOOM! The shadow is now pitch black, you can't anymore see what is in the shadow.
Or say the ambient light came back again (what a relief), but all the sudden the omni light stopped working. (probably my fault :( ) Everything now is lighted the same, no shadow, no difference, but if you lay a paper on the table, and look at it from above, there is no shadow! So you think it is part of the table! In a world like this your rely on the contour of something in order to see it- you would have to look at the table from side view, to see the thickness of the paper.
Hope this helps (at least a little)
Note: ambient lighting give a similar effect to emissive material