Convert an image to a SceneKit Node

Question

I have a bit-map image:

( However this should work with any arbitrary image )

Answer 1

Now you drawing each pixel as SCNBox of certain color, that means:

• one GL draw per box
• drawing of unnecessary two invisible faces between adjancent boxes
• drawing N of same 1x1x1 boxes in a row when one box of 1x1xN can be drawn

Seems like common Minecraft-like optimization problem:

1. Treat your image is 3-dimensional array (where depth is wanted image extrusion depth), each element representing cube voxel of certain color.
2. Use greedy meshing algorithm (demo) and custom SCNGeometry to create mesh for SceneKit node.

Pseudo-code for meshing algorithm that skips faces of adjancent cubes (simplier, but less effective than greedy meshing):

#define SIZE_X = 16; // image width
#define SIZE_Y = 16; // image height

// pixel data, 0 = transparent pixel
int data[SIZE_X][SIZE_Y];

// check if there is non-transparent neighbour at x, y
BOOL has_neighbour(x, y) {
    if (x < 0 || x >= SIZE_X || y < 0 || y >= SIZE_Y || data[x][y] == 0)
        return NO; // out of dimensions or transparent
    else
        return YES; 
}

void add_face(x, y orientation, color) {
    // add face at (x, y) with specified color and orientation = TOP, BOTTOM, LEFT, RIGHT, FRONT, BACK
    // can be (easier and slower) implemented with SCNPlane's: https://developer.apple.com/library/mac/documentation/SceneKit/Reference/SCNPlane_Class/index.html#//apple_ref/doc/uid/TP40012010-CLSCHSCNPlane-SW8
    // or (harder and faster) using Custom Geometry: https://github.com/d-ronnqvist/blogpost-codesample-CustomGeometry/blob/master/CustomGeometry/CustomGeometryView.m#L84 
}

for (x = 0; x < SIZE_X; x++) {
    for (y = 0; y < SIZE_Y; y++) {

        int color = data[x][y];
        // skip current pixel is transparent
        if (color == 0)
            continue;

        // check neighbour at top
        if (! has_neighbour(x, y + 1))
            add_face(x,y, TOP, );

        // check neighbour at bottom
        if (! has_neighbour(x, y - 1))
            add_face(x,y, BOTTOM);

        // check neighbour at bottom
        if (! has_neighbour(x - 1, y))
            add_face(x,y, LEFT);

        // check neighbour at bottom
        if (! has_neighbour(x, y - 1))
            add_face(x,y, RIGHT);

        // since array is 2D, front and back faces is always visible for non-transparent pixels
        add_face(x,y, FRONT);
        add_face(x,y, BACK);

    }
}

A lot of depends on input image. If it is not big and without wide variety of colors, it I would go with SCNNode adding SCNPlane's for visible faces and then flattenedClone()ing result.