SceneKit

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Create 3D games and add 3D content to apps using high-level scene descriptions using SceneKit.

SceneKit Documentation

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SCNGeometry and .copy()
Up to now I have created multiple new SCNNodes using an instance of SCNGeometry and it was OK that they all had the same appearance. Now I want variety and when I make a copy of that instance using: let newGeo = myGeoInstance.copy() as! SCNGeometry (must be force cast because copy() -> any?) all elements are verified present. :-) Likewise: node.geometry?.replaceMaterial(at: index, with: myNewMaterial) is verified to correctly change the material(s) at the correct index(s). The only problem is the modified "teapot" is not visible, and yes I have set node.isHidden = false. Has anyone experienced this? In the old days reversing the verts was a solution. In desperation I tried that. |-(
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795
Dec ’24
SCNCamera SSAO on visionOS
Hi Looking at the documentation for screenSpaceAmbientOcclusionIntensity, I noticed that it says this is supported on visionOS 1.0+: https://developer.apple.com/documentation/scenekit/scncamera/screenspaceambientocclusionintensity Could someone enlighten me as to how that would work? As far as I know, we don't use an SCNCamera on visionOS. So, what's the idea here? Can we activate SSAO on visionOS?
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392
Feb ’25
Swift game sometimes runs on efficiency cores then snaps back to performance cores
I've been working on Swift game which is not yet launched or available for preview. The game works in such a way that it has idle CPU while the user is thinking and sustained max CPU and GPU on as many cores as possible when he makes a move. Rarely, due to OS activity or something else outside of my control (for example when dropping the OS curtain even if for just a bit then remove it), the game or some of its threads are moved to efficiency cores which results in major stuttering which persists precisely until the game is idle again at which point the game is moved back on performance cores - but if the player keeps making moves the stuttering simply won't go away and so I guess compuptation is locked onto efficiency cores. The issue does not reproduce on MacCatalyst on Intel. How do I tell Swift to avoid efficiency cores? BTW Swift and SceneKIT have AMAZING performance especially when compared to others.
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91
Mar ’25
SCNTechnique clearColor Always Shows sceneBackground When Passes Share Depth Buffer
Problem Description I'm encountering an issue with SCNTechnique where the clearColor setting is being ignored when multiple passes share the same depth buffer. The clear color always appears as the scene background, regardless of what value I set. The minimal project for reproducing the issue: https://www.dropbox.com/scl/fi/30mx06xunh75wgl3t4sbd/SCNTechniqueCustomSymbols.zip?rlkey=yuehjtk7xh2pmdbetv2r8t2lx&st=b9uobpkp&dl=0 Problem Details In my SCNTechnique configuration, I have two passes that need to share the same depth buffer for proper occlusion handling: "passes": [ "box1_pass": [ "draw": "DRAW_SCENE", "includeCategoryMask": 1, "colorStates": [ "clear": true, "clearColor": "0 0 0 0" // Expecting transparent black ], "depthStates": [ "clear": true, "enableWrite": true ], "outputs": [ "depth": "box1_depth", "color": "box1_color" ], ], "box2_pass": [ "draw": "DRAW_SCENE", "includeCategoryMask": 2, "colorStates": [ "clear": true, "clearColor": "0 0 0 0" // Also expecting transparent black ], "depthStates": [ "clear": false, "enableWrite": false ], "outputs": [ "depth": "box1_depth", // Sharing the same depth buffer "color": "box2_color", ], ], "final_quad": [ "draw": "DRAW_QUAD", "metalVertexShader": "myVertexShader", "metalFragmentShader": "myFragmentShader", "inputs": [ "box1_color": "box1_color", "box2_color": "box2_color", ], "outputs": [ "color": "COLOR" ] ] ] And the metal shader used to display box1_color and box2_color with splitting: fragment half4 myFragmentShader(VertexOut in [[stage_in]], texture2d<half, access::sample> box1_color [[texture(0)]], texture2d<half, access::sample> box2_color [[texture(1)]]) { half4 color1 = box1_color.sample(s, in.texcoord); half4 color2 = box2_color.sample(s, in.texcoord); if (in.texcoord.x < 0.5) { return color1; } return color2; }; Expected Behavior Both passes should clear their color targets to transparent black (0, 0, 0, 0) The depth buffer should be shared between passes for proper occlusion Actual Behavior Both box1_color and box2_color targets contain the scene background instead of being cleared to transparent (see attached image) This happens even when I explicitly set clearColor: "0 0 0 0" for both passes Setting scene.background.contents = UIColor.clear makes the clearColor work as expected, but I need to keep the scene background for other purposes What I've Tried Setting different clearColor values - all are ignored when sharing depth buffer Using DRAW_NODE instead of DRAW_SCENE - didn't solve the issue Creating a separate pass to capture the background - the background still appears in the other passes Various combinations of clear flags and render orders Environment iOS/macOS, running with "My Mac (Designed for iPad)" Xcode 16.2 Question Is this a known limitation of SceneKit when passes share a depth buffer? Is there a workaround to achieve truly transparent clear colors while maintaining a shared depth buffer for occlusion testing? The core issue seems to be that SceneKit automatically renders the scene background in every DRAW_SCENE pass when a shared depth buffer is detected, overriding any clearColor settings. Any insights or workarounds would be greatly appreciated. Thank you!
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119
Jun ’25