This patch started out as a prototype for a retopology overlay. Before we started there were
several ideas how to tackle this issue (Frontface Backface and average back+front face shifting)
In the end we go the best results by mixing back and front depth buffers including a slider. With
this situation users can control what suits best for their needs.
And this patch needs a lot of testing it changes the Depth buffer and by doing that it can
intervene with the workings of other tools that needs the original depth buffer.
- When using modifiers make sure you project the edge cage on the modifiers. Otherwise the geometry generated by the modifiers will not be visible as it is not part of the edit data. In edit mode a shaded version of the mesh is drawn by the active render engine, but for retopology we can't. There not a good way how to solve this.
- When slider is set to 0.0 we should not do any depth testing. As backfaces could become visible we should separate the color drawing and the alpha blending.
- Improve snapping tools with a collection to snap against. As how we could see it this collection might be select-able per mesh. The snapping tools will have an option to use this collection. (Use Retopology Collection) This needs further design.
- After the snapping tools we could improve the drawing of the retopology overlay by only looking at the depth of objects that are in the depth buffer.
- Add option to draw the retopology faces using other colors like material viewport colors or vertex colors.
- Enable this addon when in sculpt mode. The new overlay engine should support this, but sculpt drawing is always a hassle so will not include that in the first release.