Trying to merge blueprint actors, I found that this does not work as I expect when using dynamic material instances. I have a material and want to use different UV offsets, so that I can achieve seamless texturing when placing wall segments of different sizes with. In the below image, left and right meshes use some offset, while the middle one has U offset 0, so that all 3 segments are seamless.
I am using blueprint based actors, create a dynamic material instance and set the offset for each of the 3 meshes in the construction script. This allows for simple control of shift using a slider.
In order to reduce draw calls, I go for actor merging. But unfortunately, after actor merge (not doing a material merge), the result is as follows:
First problem: no materials are assigned to the slots at all, so need to do that manually. Even worse, after doing this, the following happens:
There’s no way to set any material to the mesh part corresponding to the original left mesh. For some reason, only one instance can be assigned. Also tried to set the optional name parameters, no effect.
But the following works: doing the exact same merge with several readily prepared material instance assets, each one with a fixed offset, selected by a switch in this version of blueprint:
After merge, the result is immediately correct, with both slots having their textures correctly assigned and all parts of the merged mesh textured correctly.
The big disadvantage with this: I need to create a whole bunch of predefined material instances for the different offsets and the different base materials, which is something I wanted to avoid by using dynamic material instances.
Also interesting: If I go for merging materials, both versions work. Merging the materials could even more reduce draw calls, but I found, that the final texturing gets more blurry, even if setting the texture size to double the value of the original ones. Need to experiment more.