We can use UV mapping to unroll a 3D surface to a 2D plane. Apart for applying textures to your model we can use the UV´s to cut fabric for our composites.
We will apply a checker pattern to our model as a visual reference. This helps us to verify that the proportions and resolution is the same on all UV’s.
First change render mode from Blender Render to Cycles Render
Add material to your mesh. Under surface make sure it is a Diffuse BSDF
We want to creat a temporary unwrap so we can see the generated texture we are about to apply.
Select your mesh,
Drag out a new work window by click and drag on the diagonal stripes in the Bottom left corner and change it to UV/Image Editor
To close a workspace click and drag on the same diagonal stripes, Depending on what direction you drag the window you see an arrow indicating what workspace will collapse.
In UV editor create a new image. Image/new image (ALT N), name it and choose Generate Type UV Grid.
Change To Node Editor
Check Use Nodes to display selected mesh nodes. You might have to enlarge the UV window to see it. (Make sure your mesh is selected)
Next we want to add the texture we just created. Add/Texture/ImageTexture and select your newly created UV image
Connect Image texture color to Diffuse BSDF Color
Change display objects to material
You are now ready to start unwrapping using the checker pattern as reference
Before working with the UV´s it is a good habit to reset/freeze your transformations. Go Object /Apply/Rotate & Scale.
TAB to enter edit mode
CTRL TAB and select edges
Now you can start to select you seams. Think of it as cutting fabric for a shirt. You can select your seams by clicking or use option keys to speed up the process:
CTRL CLICK goes point to point
SHIFT CLICK select or deselect individual edge
ALT CLICK select an edge loop
CTRL E to mark you selected edges as seam (or select it in Shading UV Tab click mark Seam)
When done or want to se your result so far:
Options tab or in UV menu select live unwrap
This keeps UV and editmode mesh in sync while working.
If you got several pieces you can manipulate them with your standard Blender short cuts.
But the most useful option in our case is Pack Islands:
UVs/Pack Islands places all the UV within the workspace while keeping the proportion and proportional scale relative to each other.
When you are happy with your seams and UV layout:
Now the UV are proportional right but not in the right scale. When doing a Pack Islands Blender will scale the UV to get maximum resolution. To make sure you get the right scale for your cut file I add a 1cm x 1cm plan in my model as a reference.
For the image trace it works best if the image is a solid color and ndt just lines. Easiest way to do this is in your image editing software select the transparency, invert selection and do a fill. Now tracing the image is a breaze.
MORE INTERFACE SHORTCUTS
n toggel properties panel
t toggle tools pannel