I looked in the documentation, but I don't know how to get the texture ID.

void* texPtr = SixDegreesSDK_GetBackgroundTexture();
            if (texPtr != nil) {
                id<MTLTexture> mtlTexture = (__bridge id<MTLTexture>)texPtr;

                id<MTLDevice> device = [mtlTexture device];
                // !!! Not fond of creating a new command queue for every texture
                id<MTLCommandQueue> commandQueue = [device newCommandQueue];
                id<MTLCommandBuffer> commandBuffer = [commandQueue commandBuffer];
                id<MTLBlitCommandEncoder> blitEncoder = [commandBuffer blitCommandEncoder];

                NSUInteger textureWidth = mtlTexture.width;
                NSUInteger textureHeight = mtlTexture.height;
                NSUInteger rowbytes = mtlTexture.bufferBytesPerRow;
                MTLPixelFormat  pixFormat = mtlTexture.pixelFormat;
                CVPixelBufferRef _CVPixelBuffer = NULL;
                NSDictionary* cvBufferProperties = @{
                                                     (__bridge NSString*)kCVPixelBufferOpenGLCompatibilityKey : @YES,
                                                     (__bridge NSString*)kCVPixelBufferMetalCompatibilityKey : @YES,
                CVReturn cvret = CVPixelBufferCreate(kCFAllocatorDefault,
                                                     textureWidth, textureHeight,
                                                     (__bridge CFDictionaryRef)cvBufferProperties,
                const IOSurfaceRef surface  = CVPixelBufferGetIOSurface(_CVPixelBuffer);             // available in ios11 sdk, ios4 runtime

                MTLTextureDescriptor* textureDescriptor = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:pixFormat
                id<MTLTexture> metalTexture = [device newTextureWithDescriptor:textureDescriptor

                MTLRegion region = MTLRegionMake2D(0, 0, textureWidth, textureHeight);

                [blitEncoder copyFromTexture:mtlTexture

                [blitEncoder endEncoding];
                [commandBuffer commit];
                [self.mEAGLContext texImageIOSurface:surface target:GL_TEXTURE_2D internalFormat:GL_RGBA width:textureWidth height:textureHeight format:GL_RGBA type:GL_UNSIGNED_BYTE plane:0];
  • \$\begingroup\$ Why do you think there's a texture ID? If you had one, what would you do with it? \$\endgroup\$ Dec 8 '18 at 15:59
  • \$\begingroup\$ I'm sharing it with Ogre texture, that I need the texture ID and let ogre renders it.. \$\endgroup\$ Dec 8 '18 at 16:00
  • \$\begingroup\$ You should have specified that in your question. You should also not crosspost the same question to different Stack Exchange sites. \$\endgroup\$ Dec 8 '18 at 16:13
  • \$\begingroup\$ I edited to include the additional detail. What's that code sample doing? Isn't it exactly what you're looking for? (The value seems to be of type id<MTLTexture>.) \$\endgroup\$
    – Anko
    Dec 8 '18 at 19:46
  • \$\begingroup\$ @Anko I don't know how to call the blit command, and don't understand why I need to create an IOSurface for that purpose.. I already have the texture MTL from the SDK.. so why I need to create an IOSurface for it \$\endgroup\$ Dec 8 '18 at 21:43

Ogre does not support Metal at this time. MTLTexture does not have any concept of a texture ID. If one library is returning a MTLTexture and the other expects an OpenGL texture ID, you'll need to copy the MTLTexture into an OpenGL texture created using IOSurfaces.

The documentation on IOSurfaces is a bit slim, unfortunately. Once you have an IOSurface, you can blit the MTLTexture into it using a MTLBlitCommandEncoder. You can then retrieve an OpenGL texture from the IOSurface via CGLTexImageIOSurface2D().

It might look something like this (not actually compiled, probably needs cleaning up):

NSDictionary* properties = @{ 
    IOSurfacePropertyKeyWidth : [NSNumber numberWithInt:textureWidth],
    IOSurfacePropertyKeyHeight : [NSNumber numberWithInt:textureHeight],
    IOSurfacePropertyKeyRowBytes : [NSNumber numberWithInt:rowbytes],
    IOSurfacePropertyKeyPixelFormat : [NSNumber numberWithInt:pixFormat],
    // ... etc. with any other relevant properties
IOSurface* ioSurface = [[IOSurface alloc] initWithProperties:properties];

Next you can get a MTLTexture from the IOSurface by doing this:

MTLTextureDescriptor* textureDescriptor = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:pixFormat
id<MTLTexture> metalTexture = [metalDevice newTextureWithDescriptor:textureDescriptor

Now, I've never personally used a MTLBlitEncoder, so I don't know the gory details, but it looks like once you've created one, you can call -[MTLBlitCommandEncoder copyFromTexture:sourceSlice:sourceLevel:sourceOrigin:sourceSize:toTexture:destinationSlice:destinationLevel:destinationOrigin:]. I believe once that blit command has been completed, the IOSurface will contain the texture data. Apple has some sample code showing how to use them.

From there you can do:

GLint glTextureID = CGTexImageIOSurface2D(glContext, GL_TEXTURE_RECTANGLE_ARB, GL_RGBA, textureWidth, textureHeight, GL_BRGA, GL_UNSIGNED_INT_8_8_8_8_REV, ioSurface, 0);

(That assumes you want an 8-bit per channel RGBA texture and that the MTLTexture was in that format.)

Here's some additional sample code for sharing between Metal and OpenGL.


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