9 September 2009

Master the gradient mesh tool Illustrator

The Gradient Mesh tool is tricky to master, which leads many digital artists to play with it a few times and then leave it alone, or only use it for specific tasks. One challenge with the tool is that when the mesh is complicated, the gradation of colour between two points forms a hard line instead of a soft gradient.

There isn’t always an easy way to combat this: instead, the artist has to learn to fool the eye, and even compromise a little sometimes. In this tutorial, Stephen Freeman shows how to deal with this, guiding you step-by-step through how to create this illustration.

He’ll also illustrate the potential and limitations of the Gradient Mesh tool, and show you how to handle some of the tool’s other little niggles. Gradient meshes use a lot of power, particularly when they get complex, so be patient if your machine doesn’t boast a speedy processor.

01. Create a quick sketch. In this case, we’ve drawn a Tyrannosaurus Rex’s head. The purpose of this sketch is to lay down the shape of the head as it will appear in the final illustration. At this point it is wise to apply some colour and map out light and shadow areas. Save it as a CMYK image.

02. When you’re satisfied with the sketch, import it into Illustrator using File > Place and set the transparency to about 40 (highlight the sketch and then go Window > Transparency, or hit Shift + Cmd/Ctrl + F10). Now lock the layer (Object > Lock, or Cmd/Ctrl + 2).

03. Starting with the bottom jaw, make a basic outline of the head. It’s crucial that the shape isn’t too complicated, as this will make the mesh difficult to control. With the shape selected, fill the path with the mid-tone colour (C = 52, Y = 28, M = 67, K = 22). We will create the shadow and highlights using the mesh.

04. Select the Gradient Mesh tool and place a point near the bottom edge of the jaw line. We are trying to get the path to follow the curvature of the jaw. We will be developing the shadowed area along this line.

05. Once you’re satisfied that this line follows your contour closely enough, place another mesh line just above it. The purpose of this line is to isolate the first line you created. The reason for isolating the line is to prevent any colour you apply to it from bleeding into the area we need to reserve for midtones. With this done, apply the shadow colour (C = 61, Y = 39, M = 83, K = 76). Pull some of the mesh points beyond the viewable area of the path so that the gradient will blend smoothly.

06. Now our shadow is in place, we can define the upper shadow area. Select the same colour we used for the mid-tones and isolate the upper ridge line. This isolation preserves the colour under the protrusion. Be sure to mould this line to the shape of the protrusion with as few mesh lines as possible. We need to keep the mesh simple at this stage because we will build on it as we go along, and we don’t want it to be difficult to edit later.

07. With all your shadows in place, start adding in highlights. I find it useful to refer to my original sketch for the position of the highlights. With the Gradient Mesh tool, create a new mesh line contoured to the shape of the upper ridge, by adjusting the handles as you would with any regular path. Select a highlight colour (C = 5.5, M = 1.5, Y = 6.5, K = 0) and apply it to the line.

08. You should now have a basic bottom jaw without the skin texture. To add texture, play around with the mesh lines we already have, and add a few new ones for control. Add vertical mesh lines and bend them to match the bone structure, adding a highlight colour to the light side. This gives the impression of skin stretched over bone.

09. Add in mesh lines until it resembles a grid, then fill the grid with alternating light and dark colour to add fine texturing, like skin patterns.

10. The upper jaw, eyes and nostrils are all created from one mesh; this is the most complicated part of the illustration. Draw its silhouette and fill it with a mid-tone colour (C = 52, Y = 28, M = 67, K = 22). First isolate the eyes and the area where the nostrils will be. For the eyes, mould the mesh into the shape of the eye, and add a mesh to separate the whites from the pink parts of the eye. Fill the pupil with white and the corners with pink. Create the pupil and add brown. Add a mesh to indicate light and dark areas in the pupil.

11. For the nostril, add a mesh inside the area we isolated. Select each handle on the points and mould the path to the curvature of the nostril. Add more mesh points to indicate the shadow under the nostril and a highlight on the top.

12. When you’re creating the shadow areas on the face, be sure to use as many mesh points as necessary to accomplish the curvature of the face. Pay special attention to areas where the skin folds and creases. Don’t be afraid to pull the mesh completely outside the path. This is great for situations when you wish to create a smooth graduation of colour on the edge of a path.

13. For the horn shape over the eyes we need to create separate meshes and then blend them into the skin. First draw the shape of the horn, keeping it as simple as possible, then add a mesh. The mesh will follow the contour of the path and give form to the shape, so all you will need to do is add mesh for light and shadow.

14. We’ll need to create an individual mesh for each tooth. Once you’ve drawn each shape, add a base colour – use white for most teeth, adding a hint of yellow for some. Next, add light and shadow areas. For the darkest shadow, use 32% black and 26% yellow. For some teeth add a strong yellow up to 50%. For speed, create basic teeth, duplicate them, scale them, and reuse them to fill the mouth with teeth.

15. Handle the tongue, gums, and mouth lining in a similar manner to the skin, except use a base colour of C = 10, M = 36.5, Y = 22.3, K = 0, with a highlight of C = 10, M = 99, Y = 76.2, K = 88.7. For the crease that runs down the center of the tongue, first create a mesh, then add shadow and highlights, as before.

16. The final area is the part that connects the upper jaw to the lower jaw. We’re creating this separately to keep it simple, as complex shapes are difficult to mesh, and sometimes the Gradient Mesh tool just won’t work on a path that is too complex.

Author : Stephen Freeman

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