Since you are projecting on a wall (a flat one, I am assuming), have you considered using what we call a 2D projection mapping approach? It basically means you map the content to your projector directly from a canvas.
Then you can use warping and blending tools in Canvas setup window.
You can use Projection mapping sample project to find out more.
Also, this approach is explained in this video tutorial:
The 3D approach where you have a UV mapped OBJ object in the Visualizer and aim a virtual projector at it, is primarily aimed at projecting onto a non-flat 3D models. It requires a few more clicks to get it right. There’s also a big upgrade in this area planned for v3.2.3 .
Let me know if this helps,