改变 SCNNode/Geometry/Material 的颜色

Question

我对 SceneKit 非常陌生，并且正在开始一个测试应用程序。我有一个可以四处移动的小立方体。我想添加轴（X、Y、Z）。我是这样创建它们的。

    SCNVector3 xPositions[] = {SCNVector3Make(-50, 0, 0), SCNVector3Make(50, 0, 0)};

    int indicies[] = {0, 1};
    NSData *indexData = [NSData dataWithBytes:indicies length:sizeof(indicies)];

// X axis
    SCNGeometrySource *xSource = [SCNGeometrySource geometrySourceWithVertices:xPositions count:2];
    SCNGeometryElement *xElement = [SCNGeometryElement geometryElementWithData:indexData primitiveType:SCNGeometryPrimitiveTypeLine primitiveCount:2 bytesPerIndex:sizeof(int)];
    SCNGeometry *xAxis = [SCNGeometry geometryWithSources:@[xSource] elements:@[xElement]];
    SCNNode *xNode = [SCNNode nodeWithGeometry:xAxis];
    [self.gameView.scene.rootNode addChildNode:xNode];

    // Y axis
    SCNVector3 yPositions[] = {SCNVector3Make(0, -50, 0), SCNVector3Make(0, 50, 0)};
    SCNGeometrySource *ySource = [SCNGeometrySource geometrySourceWithVertices:yPositions count:2];
    SCNGeometryElement *yElement = [SCNGeometryElement geometryElementWithData:indexData primitiveType:SCNGeometryPrimitiveTypeLine primitiveCount:2 bytesPerIndex:sizeof(int)];
    SCNGeometry *yAxis = [SCNGeometry geometryWithSources:@[ySource] elements:@[yElement]];
    SCNNode *yNode = [SCNNode nodeWithGeometry:yAxis];
    [self.gameView.scene.rootNode addChildNode:yNode];

    // Z axis
    SCNVector3 zPositions[] = {SCNVector3Make(0, 0, -50), SCNVector3Make(0, 0, 50)};
    SCNGeometrySource *zSource = [SCNGeometrySource geometrySourceWithVertices:zPositions count:2];
    SCNGeometryElement *zElement = [SCNGeometryElement geometryElementWithData:indexData primitiveType:SCNGeometryPrimitiveTypeLine primitiveCount:2 bytesPerIndex:sizeof(int)];
    SCNGeometry *zAxis = [SCNGeometry geometryWithSources:@[zSource] elements:@[zElement]];
    SCNNode *zNode = [SCNNode nodeWithGeometry:zAxis];
    [self.gameView.scene.rootNode addChildNode:zNode];

我的问题是我想改变它们的颜色，这样我就可以分辨出哪个是哪个。有没有办法可以做到这一点，或者我必须以另一种方式创建我的线条？我正在制作一个 Mac 应用程序，而不是 iOS 应用程序，仅供参考。另外，我知道重复代码，我只是累了，我会解决这个问题。

Answer 1

使用-firstMaterial 或（如果是复杂对象）-materials 数组更改几何体的材质。

SCNMaterial *redMaterial = [SCNMaterial new];
redMaterial.diffuse.contents = [NSColor redColor];
xAxis.firstMaterial = redMaterial;

或者更简洁：

yAxis.firstMaterial.diffuse.contents = [NSColor magentaColor];
zAxis.firstMaterial.diffuse.contents = [NSColor yellowColor];