How to place text in the certain position when using SceneKit?

问题

I have tried to follow the same simple logic as for cylinder, box … , so just by defining the position for textNode, but it is not working.

func makeText(text3D: String, position: SCNVector3, depthOfText: CGFloat, color: NSColor, transparency: CGFloat) -> SCNNode
{
    let textTodraw = SCNText(string: text3D, extrusionDepth: depthOfText)
    textTodraw.firstMaterial?.transparency = transparency
    textTodraw.firstMaterial?.diffuse.contents = color
    let textNode = SCNNode(geometry: textTodraw)
    textNode.position = position        
    return textNode
}

回答1:

The default font for SCNText is 36 point Helvetica, and a "point" in font size is the same as a unit of scene space. (Well, of local space for the node containing the SCNText geometry. But unless you've set a scale factor on your node, local space units are the same as scene space units.) That means even a short label can be tens of units tall and hundreds of units wide.

It's typical to build SceneKit scenes with smaller scope — for example, simple test scenes like you might throw together in a Swift playground using the default sizes for SCNBox, SCNSphere, etc might be only 3-4 units wide. (And if you're using SceneKit with ARKit, scene units are meters, so some text in 36 "point" font is the size of a few office blocks downtown.)

Also, the anchor point for a text geometry relative to its containing node is at the lower left corner of the text. Put all this together and it's entirely possible that there are giant letters looming over the rest of your scene, hiding just out of camera view.

Note that if you try to fix this by setting a much smaller font on your SCNText, the text might get jagged and chunky. That's because the flatness property is measured relative to the point size of the text (more precisely, it's measured in a coordinate system where one unit == one point of text size). So if you choose a font size that'd be tiny by screen/print standards, you'll need to scale down the flatness accordingly to still get smooth curves in your letters.

Alternatively, you can leave font sizes and flatness alone — instead, set a scale factor on the node containing the text geometry, or set that node's pivot to a transform matrix that scales down its content. For example, if you set a scale factor of 1/72, one unit of scene space is the same as one "inch" (72 points) of text height — depending on the other sizes in your scene, that might make it a bit easier to think of font sizes the way you do in 2D.

来源：https://stackoverflow.com/questions/41066865/how-to-place-text-in-the-certain-position-when-using-scenekit

标签

swift3

scenekit

textnode