Combining two or more SCNGeometries

Question

I made this method to capture UIImage and turn it into a 3D model. However, this means that I am adding to many nodes. I thought maybe it could be optimized by adding all the geometries to one node. Is there any way to do this?

Here is the code

static inline SCNNode* S2NNode(const UIImage* sprite) {
  SCNNode *spriteNode = [SCNNode node];
  CFDataRef pixelData = CGDataProviderCopyData(CGImageGetDataProvider(sprite.CGImage));
  const UInt8* data = CFDataGetBytePtr(pixelData);
  for (int x = 0; x < sprite.size.width; x++)
  {
    for (int y = 0; y < sprite.size.height; y++)
    {
      int pixelInfo = ((sprite.size.width * y) + x) * 4;
      UInt8 alpha = data[pixelInfo + 3];
      if (alpha > 3)
      {
        UInt8 red   = data[pixelInfo];
        UInt8 green = data[pixelInfo + 1];
        UInt8 blue  = data[pixelInfo + 2];
        UIColor *color = [UIColor colorWithRed:red/255.0f green:green/255.0f blue:blue/255.0f alpha:alpha/255.0f];
        SCNNode *pixel = [SCNNode node];
        pixel.geometry = [SCNBox boxWithWidth:1.001 height:1.001 length:1.001 chamferRadius:0];
        pixel.geometry.firstMaterial.diffuse.contents = color;
        pixel.position = SCNVector3Make(x - sprite.size.width / 2.0,
                                        y - sprite.size.height / 2.0,
                                        0);
        [spriteNode addChildNode:pixel];
      }
    }
  }
  CFRelease(pixelData);
  //The image is upside down and I have no idea why.
  spriteNode.rotation = SCNVector4Make(1, 0, 0, M_PI);
  return spriteNode;
}

Answer 1

This answer addresses the initially asked question - how to combine geometries. However, merging geometries does not seem to be the solution to your real problem - how to get a pixel sprite with a certain thickness, with decent performance. See my other answer for this.

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Answer 2

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UIImage *image = [UIImage imageNamed:@"sprite"];
UIBezierPath *path = PathFromImage(image); // Make or load your path here
SCNNode *node = [SCNNode nodeWithGeometry:[SCNShape shapeWithPath:path extrusionDepth:1]];
SCNMaterial *face = [SCNMaterial material];
face.diffuse.contents = image;
face.diffuse.magnificationFilter = SCNFilterModeNone;
SCNMaterial *side = [SCNMaterial material];
side.diffuse.contents = [UIColor blackColor];
side.specular.contents = [UIColor whiteColor];
node.geometry.materials = @[ face, side, side ];

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