To clarify this point…
Within a ‘group’ of layers, the OpenGL Add / Over modes are mutually exclusive with the more advanced composition modes (CoreImage, GLSL, Quartz Composer). VDMX will automatically switch the comp modes for layers within a group to handle this.
A few notes:
- You will get the best performance when using OpenGL Add & Over modes. Use these whenever possible, especially for very high resolution situations!
- If using the more advanced options for composition, we recommend using the GLSL modes whenever possible (here is a tutorial on making your own GLSL comp modes, https://vdmx.vidvox.net/tutorials/making-glsl-composition-modes-for-vdmx)
- The VVSourceAtop.fs is the closest match to OpenGL Over mode.
- This is a subtle detail in advanced cases – when you are doing compositing with multiple sub-groups of layers and you are using both alpha channels and opacity for blending, and you need the alpha channels to be preserved when that sub-group gets composited with other layers or groups, within your sub-groups you may need to use the GLSL modes instead of the OpenGL Add / Over modes. I can post an example of this to demonstrate if it’d be useful.