helix-toolkit | Helix Toolkit is a collection of 3D components for .NET

C#, WPF, Helix Toolkit. I am trying to save an image from a HelixViewport3D viewport (as described here) and am still having problems.

Intended method: Render image to viewport and simply save that using Viewport3DHelper.SaveBitmap() or similar method.

Follow-on question to this one.

I am trying to generate and save a series of images. Rendering is done by Helix Toolkit, which I am told utilises the WPF composite render thread. This is causing problems because it executes asynchronously.

My original problem was that I couldn't save a given image because it hadn't yet been rendered at that time I was trying to save it. The above answer provides a workaround to this by putting the 'save' operation inside an Action which is called with low priority, thus ensuring that the rendering completes first.

This is fine for one image, but in my application I require multiple images. As it stands I cannot keep control of the sequence of events because they occur asynchronously. I am using a For loop which just continues regardless of the progress of rendering and saving the images. I need the images to be generated one by one, with enough time for rendering and saving before starting the next one.

I have tried putting delays in the loop but that causes its own problems. For instance an async await as commented in the code causes cross-threading issues because the data was created on a different thread from where the rendering is being done. I tried putting in a simple delay but then that just locks everything up - I think in part because the save operation I am waiting on has very low priority.

I cannot simply treat it as a batch of separate unrelated asynchronous tasks because I am using a single HelixViewport3D control in the GUI. The images have to be generated sequentially.

I did try a recursive method where SaveHelixPlotAsBitmap() calls DrawStuff() but that wasn't working out very well, and it doesn't seem a good approach.

I tried setting a flag ('busy') on each loop and waiting for it to be reset before continuing but that wasn't working - again, because of the asynchronous execution. Similarly I tried using a counter to keep the loop in step with the number of images that had been generated but ran into similar problems.

I seem to be going down a rabbit hole of threading and asynchronous operations that I don't want to be in.

How can I resolve this?

C#, WPF, Helix Toolkit. I am trying to generate a bitmap from a HelixViewport3D and have encountered a few problems.

The first problem is that I cannot find a way to render off-screen. There are a few references to this online (e.g. here) and as far as I can see it does not have a built-in solution.

As a somewhat sub-optimal workaround I have proceeded to render to the screen where the user can see it, with the intention of creating a bitmap from that rendered image. I now have the problem that an image exported from the content on screen (e.g. using Viewport3DHelper.SaveBitmap) is blank if I call it immediately. I understand that this is because Helix Toolkit is rendering the image in the WPF composite render thread, so there is no image to grab at the time I try to grab it, because it has not yet been rendered.

I am not aware of a 'render complete' event that I can subscribe to. Is there one?

If not, would a workaround perhaps be to use thread priorities in order to make my code lower priority, so that it waits for the rendering to complete before continuing?