Cannot create a Screenshot of a SCNView

Question

Is it possible to get a screenshot of an SCNView? I\'m trying with the below code, but it always comes out white...

NSRect bounds = [window.contentView bound         


        

Answer 1

SceneKit uses an OpenGL context to draw. You can't turn that into PDF data as easily as a Quartz based context (as used by "normal" AppKit views).
But you can grab the rasterized bitmap data from OpenGL:

- (IBAction)takeShot:(id)sender
{
    NSString* path = @"/Users/weichsel/Desktop/test.tiff";
    NSImage* image = [self imageFromSceneKitView:self.scene];
    BOOL didWrite = [[image TIFFRepresentation] writeToFile:path atomically:YES];
    NSLog(@"Did write:%d", didWrite);
}

- (NSImage*)imageFromSceneKitView:(SCNView*)sceneKitView
{
    NSInteger width = sceneKitView.bounds.size.width * self.scene.window.backingScaleFactor;
    NSInteger height = sceneKitView.bounds.size.height * self.scene.window.backingScaleFactor;
    NSBitmapImageRep* imageRep=[[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL
                                                                       pixelsWide:width
                                                                       pixelsHigh:height
                                                                    bitsPerSample:8
                                                                  samplesPerPixel:4
                                                                         hasAlpha:YES
                                                                         isPlanar:NO
                                                                   colorSpaceName:NSCalibratedRGBColorSpace
                                                                      bytesPerRow:width*4
                                                                     bitsPerPixel:4*8];
    [[sceneKitView openGLContext] makeCurrentContext];
    glReadPixels(0, 0, (int)width, (int)height, GL_RGBA, GL_UNSIGNED_BYTE, [imageRep bitmapData]);
    [NSOpenGLContext clearCurrentContext];
    NSImage* outputImage = [[NSImage alloc] initWithSize:NSMakeSize(width, height)];
    [outputImage addRepresentation:imageRep];
    NSImage* flippedImage = [NSImage imageWithSize:NSMakeSize(width, height) flipped:YES drawingHandler:^BOOL(NSRect dstRect) {
        [imageRep drawInRect:dstRect];
        return YES;
    }];
    return flippedImage;
}

Don't forget to link OpenGL.framework and #import "OpenGL/gl.h"

Update
SceneKit seems to use a flipped context. I added some code to fix the upside-down image.

Update 2
Updated code to take the backing scale factor into account (for retina displays)