Problem: I\'m trying to render a dynamic Julia fractal in real time. Because the fractal is constantly changing, I need to be able to render at least 20 fra
To cover the questions: Yes, OpenCL can paint, but Monogame apparently doesn't encapsulate over the top of CL, so No to Question 1. Question 2 is the right question: maybe, see suggestions below. Question 3: HLSL is essentially PS 1.1 so "why isn't it possible" is because PS evolved to 2.x to manage parallelization through wider data pipes...so you want Dx12 support or GLSL/OpenGL.
Since you are close to your performance expectations using CLoo, why not try OpenCL.Net and/or OpenTK to bind the Julia calculations more closely to the Monogame API? --If you have to go GPU-CPU-GPU at least make that as wide a pipeline as possible.
Alternately, a slightly sideways solution to your parallelization and framerate problem might be integrating GP-GPU wrappers such as Quanta's Alea with your Monogame solution. I'd suggest looking at Cudafy, but Alea is more robust and cross-vendor GPU supported.
The build process will decide which portion of the Julia code will calculate on GPU via Alea, and the Monogame portions will receive the pixel-field for rendering. The sticking points will be library "play-nice" compatibility, and ultimately, frame-rate if you get it working.
Bottom line: you're stuck, by choice, in HLSL (read: Microsoft Dx9) and Monogame doesn't support GLSL/Dx12....so you will have to maneuver creatively to get un-stuck.