Difficulty getting food stain removed

Mocha Pro
#1

I am evaluating Mocha Pro and have been working day and night all week trying to learn this program but am continuing to get substandard results. Here is the problem. I am attempting to do a blemish removal of a food stain on the lower lip area of a child. This is further complicated by the fact that he is chewing, he also at some point brings some food to his mouth and eats it, and he also turns his head fully to the side. The clip is over 400 frames. At the most I can get a clean plate that is acceptable for maybe 3-5 frames, but even then it is not optimal except maybe on the initial frame…maybe. I have either not properly figured out how to properly use more than one cleanplate or the fix is not happening within the xspline to be removed. Because of its close proximity to the lower lip, using interpolate brings in weird bright lip fragments, linear is slightly better but the closest I get to something usable would be using the blend but then it will look unnatural towards the ends with either too bright . too dark sections or outlines in weird places affecting it. I have redone it multiple times utilizing the training tips online and have made a little progress but nothing approaching usable or time saving. I would really like to get a handle on this program as if it works like it appears to it can be a time saver when I get into production mode but I am just about ready to end this experiment so I am reaching out to see if there is a better way.

Here is my current approach. I have 3 layers. The background layer is an oval that cuts across the front of the face from the lower nose to under the chin and half a cheek on each side. It appears to track fairly stable within around a 45 frame section that I am currently experimenting with. The stain layer is a fairly close cropped xspline around the stain. Setting up a grid for it has been problematic because of all of the stretching and changes from chewing. The stain comes up right to the lips edge and parts sometimes get caught in shadows during the downcycle of chewing and at other points the stain seems to be stretched all the way to the corner of the mouth. Tracking on this layer takes lots of keyframes, sometimes it seems like an adjustment is needed every frame to get it to track to the lip but not go over and then deal with the stretching. The stain layer is linked to the background track. The final layer is the hand layer and is the closest layer. It starts off with a small half eaten sweet pepper with stem and then he bites it, chews and releases the stem. During the process he is chewing and heavily distorting the mouth while the hand is moving over and around the stain. For the purposes of my last experiment, I did not get to the heavily complicated area and focused on mostly a direct full face and some lighter chewing. Despite my best attempts though, I have to adjust every frame during the hand section and it seems whenever I do that I get horrible end results. I have tried to be less aggressive on the full face section but the chewing and proximity of the lip makes it very difficult. All of the examples that I saw online were simple blemish removals and I could not find any examples of using multiple cleanplates, nor utilizing the frames before/frames after settings so I am not sure if I have been doing that right also. On some sections I will get a few good frames and then it starts to get ugly and in some cases it looks like a moon going through its stages from full to new.

So any help I can get to try and solve this would be greatly appreciated.

#2

Hi there,

I’d have to see this shot to truly evaluate it, but I imagine there’s lots of shadows and edges that mocha’s illumination modeling is picking up on. This might be best handled with an eye to rebuilding the blemish section, not trying to remove the blemish. That’s because illumination modeling works like the heal tool, it takes color information from the regions around the spline, so shadows will affect the whole shape. This may be best handled with the insert tool and a patch instead, and some delicate roto work.

 

If you send the shot to maryp@imagineersystems.com I will be happy to look at the shot for you.

Cheers,
Mary

#3

Yeah, there were some frames that looked a bit too Dali-ish. I emailed the clip… On another section I tried to roto I got a nice few frames from the cleanplate and then there was a mix of the shot moving into shadow so that the cleanplate adjustment was too light and also that the fixed section began to shift like a moon heading from full to quarter. I tried to change the roto position and the grid and re-render but did not notice much difference (regarding the moon effect.) I also tried a second cleanplate and adjusted for that frame then rerendered but also no difference. Is there a way of viewing where the fix is when it is out of range or get a clearer sense of where the fixed part will render?

#4

Hi there,

I took a look at your shot. The remove tool is not the best option for this shot in particular, because you’ll need to account for the hand moving over the area, and the shadow play. This shot is instead something you would want to track inside mocha and hook rotopaint in AE or Nuke up to in a comp. And you’ll need a rock solid track. I’d try tracking an area by his nose on the food stain side and then adding to x-pline on that layer to continue tracking his chin on the same side. I would then use that data to build a patch, and roto-paint any errors out.

When you have shadows moving over the top of a remove, the remove tool has limited functionality with illumination modeling, this is because of the way the tools work. In some cases, if you try interpolate, it will be enough. But linear will not be. Think of how the heal tool works in photoshop, we work in a similar way.

If the grid is not lining up with your tracking area, there’s a problem with your track. The roto never tells you how your track is going, only the surface and grid tools. Understanding what the planar tracker is looking for is a key component to getting good work out of mocha. Have you watched the mocha fundamentals? http://www.imagineersystems.com/video/?tagFilter=mocha%20Fundamentals&dd=dateOld&orderby=date&order=ASC

As for making a new cleanplate and seeing how they blend, you just have to look at the solve and see where is it off. You should be able to see right away where more cleanplates are needed because you’ll see the biggest divergence from the other cleanplates.

But like I said, the remove tool is not the best option for this shot. A more advanced rotopaint and tracking technique is needed.