Dmitriy Potrivaev

Hi guys,

I found this topic while fighting the same issue of OpenGL ROP not rendering when executing with the TOP network. Even though my post is 1-2 years later compared to the discussion I still want to add my 50 cents hoping it will help somebody in the future

So, first of all, the reason why OpenGL ROP not working in TOP is that by default the ROP OpenGL Render TOP node launches its tasks in Out-of-Process mode. This means starting a new Houdini session without GUI and doing the task's calculation in the background. But the problem is OpenGL, as it exists now, requires some GUI canvas for initialization and rendering. I'm not sure about another OS but for me, under Linux, this works like this. The same situation with error will be if you start OpenGL ROP rendering using the command prompt because at the end no GUI canvas exists.

The issue, as you may understand, is not related to Houdini itself, it's an OpenGL issue or better say the logic of how it was built and works.

One solution that works for TOP is just to change the ROP OpenGL Render TOP node from Out-of-Process to In-Process mode. That launch tasks execution for this TOP node in the same opened Houdini program and OpenGL will get all it needs for the proper initialization and rendering. But it won't solve the issue with command prompt launch of the scene execution.

The solution that SideFX support suggests works great even in the command prompt and scripts! So, thanks, guys, for sharing this! It helped me to solve the issue with OpenGL!

Hi guys,

Sorry for the late reply. In my case I use this solution: I separated each unique tag from the main flow in Houdini and sent that data to the unique Output SOP in my asset. For example, I have 3 unique tags: trees, flowers, and water. In the Houdini asset, I have 50 different curves that randomly assign these tags to them. So, I separated them by those 3 tags and sent each unique tag to its own output. For example, 25 curves with "trees" tag go to Output 0, 15 curves with "flowers" tag go to Output 1, and the other 10 curves with "water" tag go to Output 2. In the end, I have one asset that generates inside UE 50 curves but with different tags on them. Of course, you need to increase the amount of outputs in your asset type properties window.
I've attached a few screenshots below.

I don't know if is this the right approach and does it has some disadvantages but it works for me and I hope it may be useful to somebody else.

Hi pennyw,

I wonder did you find a solution yet?