Drawing a Tracer-aided matte entails four basic steps.

To draw a Tracer-aided matte:

1. Analyse the image to determine which areas are appropriate for pickers and which areas are better served by advanced gradients.
2. Draw the garbage mask.
3. Assign pickers to vertices where they are needed.
4. Adjust the softness borders, offsets, tangents, vertices, and pickers (where used).

To analyse the image:

1. Examine the edges of your talent to decide which portions would benefit from advanced gradient treatment and which would respond better to localized key treatment. If your clip has colours that change greatly throughout the clip, using pickers may be difficult.

   For more information, see Applying Softness Using Pickers.

To draw the garbage mask:

1. In the Modular Keyer or Batch, add a context point further down the processing pipeline or processing tree. You can then use the Context view to see the effect of the matte on the result image.
   NoteWhen using the Tracer to pull a key from the Modular Keyer, remove the nodes before the GMask node in the default pipeline.
2. Display the Garbage Mask menu.
3. From the View box, select Reference.

   This view is a reference image of the clip (it is not affected by your changes in the module).

4. Draw a garbage mask around the subject and close it by clicking the first vertex drawn. Use as many vertices as required to adequately enclose the subject, but try to avoid excessive vertices. This will minimize unnecessary tweaking and manipulation later.
   TipPlace more vertices in areas with variation in the background.

To assign pickers to selected vertices:

1. From the Edge Softness box, select Tracer.

   The Tracer menu appears, and two softness borders (the green lines) are added to the mask.

   
   

   (a) Edge Softness box  

2. Select the vertices to which you want to apply pickers. See Selecting Vertices and Tangents.
3. Enable Pickers.
   NoteWhen one or more pickers are enabled, mask characteristics are automatically set to Outside disabled and a Colour value of 0 so that the mask will be white inside and black outside. Do not set the Outside button unless you want to reverse the effect.

   A pair of pickers is provided for each selected vertex.

   
   

   (a) Softness borders  (b) Picker  

   • On vertices without pickers, the softness borders delineate the area where a softness gradient is applied.
   • On vertices with pickers, the softness borders delineate the area to which softness is applied according to the picker values.

To fine-tune the matte:

1. Adjust the softness borders and mask border by moving the vertices and tangents:
   • The mask border should follow the general contour of the subject as closely as possible.
   • The outer softness border should completely surround all details that you want to include in the matte—all wispy details and edges must be within this line.
   • The inner softness border should be well within the area where softness control is needed.

   When moving tangents, you can opt to have the pickers follow the tangent movement (the default behaviour), or be independent of tangent movement. To make pickers independent of tangents, switch to Break mode and click either picker. You can animate this behaviour. See Animating a Tracer Mask.

   NoteIf the tangents are broken, the pickers are automatically unlinked from the tangents.
2. For each pair of pickers, one requires a sample of the area outside the mask, while the other requires a sample of the mask interior.

   Place one picker outside the subject to sample values you do not want to include in the matte (for example, a blue screen). Place the other picker within the subject for a colour value sample of an area you do want included in the matte. Try to select areas where the colour values do not change too much throughout the clip.

3. Click Matte or Result (Matte will provide a clearer view) to see your progress.
4. Scale the pickers by doing one of the following:
   • Select Scale edit mode, click within the picker, and drag to the left to reduce the size or to the right to increase the size.
   • Select the picker and then drag the cursor over the Sample Size field.
5. Move the pickers around and enlarge or reduce them to interactively see how you can obtain the best results. This will require toggling between the Front and Matte views.

   The following figure illustrates the Matte view result of the pickers placed in the previous figures.