Drawing 3D view to RenderTarget not working on iOS

PaulH

One of my games uses 3D models to create 2D sprites by drawing the 3D view to RenderTargets. Using any of the more recent Gideros versions (at least since 2023-07) it works fine except when running on iOS. It works on Android, the Gideros player on Windows and MacOS, but on iOS nothing appears on the RenderTarget, so all the dynamically generated 2D sprites are empty. I believe it worked on all platforms when I was using Gideros 2022-12.

The issue can be reproduced by adding the code below to an existing app and running on iOS. After a few seconds it will create a 3D cube (using the code from the 3D Cube example) and add it to the stage, then draw it to a render target, make a bitmap and add that to the stage. When working correctly you should see the rotating 3D cube appear, and a stationary copy of the cube (the 2D sprite from the RenderTarget) off to the right. On iOS the rotating 3D cube is there, but the stationary one from the RenderTarget is missing:

Timer.delayedCall(5000, function() local function face(color,rx,ry) -- Create a colored face c=Sprite.new() s=Shape.new() s:setFillStyle(Shape.SOLID, color,0.8) s:beginPath() s:moveTo(-1,-1) s:lineTo(-1,1) s:lineTo(1,1) s:lineTo(1,-1) s:lineTo(-1,-1) s:endPath()   s:setZ(-1) c:addChild(s) c:setRotationX(rx) c:setRotationY(ry) return c; end   --Create a cube cube=Mesh.new(true) cube:addChild(face(0xFF0000,0,0)) cube:addChild(face(0xFFFF00,90,0)) cube:addChild(face(0xFF00FF,-90,0)) cube:addChild(face(0x00FF00,180,0)) cube:addChild(face(0x00FFFF,0,90)) cube:addChild(face(0x0000FF,0,-90))   --Set up the 3D view and projection local sw,sh=800,600 local projection=Matrix.new() projection:perspectiveProjection(45,sw/sh,0.1,1000) local view=Viewport.new() view:setProjection(projection) view:setPosition(sw/2,sh/2) view:setScale(-sw/2,-sh/2,1) stage:addChild(view)   --Add our cube to the scene view:setContent(cube) --Look at it from -8 units in Z direction view:lookAt(0,0,-8,0,0,0,0,1,0)   cube:setRotationX(20) cube:setRotationY(49) cube:setRotation(30) cube:addEventListener(Event.ENTER_FRAME,function () cube:setRotationX(cube:getRotationX()+1) cube:setRotationY(cube:getRotationY()+1.2) cube:setRotation(cube:getRotation()+1.3) end)     -- Draw the cube the the render target and add a Bitmap using it to the stage, offset from the 3D version: local rt = RenderTarget.new(800, 600) rt:draw(view) b = Bitmap.new(rt) b:setPosition(300, 0) stage:addChild(b) end )

Any ideas?

hgy29

I confirm it wasn't working, not sure since when exactly but probably since I fixed something about depth buffer which was previously ignored. It turns out Metal engine was reversing depth coordinates for RT (as OpenGL does), which is wrong for Metal.
I fixed it now: https://github.com/gideros/gideros/commit/4a3d0bb8ec3541171ec1b1c3cea385c37ce425c2

PaulH

Thanks so much for the quick fix! Any idea when a new build will be available?

PaulH

I'm still working on confirming it, but it seems that this same thing happens on UWP. 3D meshes load and render to the screen just fine, but they don't show up when drawn to RenderTargets.

hgy29

Honestly I am struggling with this one, I fixed it several times but it seems to reappear once in a while, I will try to reproduce and debug once more. It is usually caused by wrong projection or wrong depth buffer, which are reversed on Metal and DirectX as compared to OpenGL.
If 2D still works, then it would probably be depth buffer thing.

hgy29

So indeed, exactly the same as thing as for Metal. So same fix: https://github.com/gideros/gideros/commit/80ae6edc0a51fa5aa2bad38bb7c3cb3bd9d271a1