With practice, use of these advanced design principles will improve the designer's skill and expertise in creating good tactile graphics. Designing is not an exact science and so it may not always be possible to use all of these principles in your designs every time. However, general application of them to your design will help you to produce images that are well thought out and a good experience for the user.
Points to consider:
-
As a tactile image is constructed from lines and textures it is good practice to use different line types for different components. When choosing the line and texture values for the various components of the image it is necessary to prioritise their relative importance. The more important components can have stronger textures and thicker lines with the less important components having background textures and thinner lines. For example on a line graph the data line would be the thickest line, the axis lines would be a medium weight and the grid could be really quite thin.
-
A solid texture should be used for more important items on the image as a solid texture will raise more and be more noticeable to the user than light textures.
-
Components which have a different meaning or identity should have a different texture fill to express this. Some textures which look different can be really indistinguishable by touch so it is important to have good texture differentiation in an image to avoid misinterpretation by the user.
-
Consistency of textures is particularly important across a series of related images as it enables the user to make a link of the same texture being used for the same component across the images. For example in a series of maps always use the same texture for the sea and oceans.
-
It is useful for a shape to be filled with a texture so that a blind reader will know whether they are inside or outside of the shape.
-
To avoid the appearance of various objects merging together it is good practice to ensure the various components of an image are clear so that they cannot be misunderstood. It is sometimes necessary to have a gap of few millimetres between components to enable this to happen. For example a book could visually appear to float above the table it is placed on, but the gap between will not be felt tactually.
-
Thin and medium lines which cross a texture often benefit from a thicker white line behind them so that they do not disappear into the texture.
-
Be aware that when large areas of solid fill are raised on swell paper they may over raise compared to the other less dense elements and crumble off.
-
Using textures and dots in the image which are the same size as braille can confuse the reader who may not be able to distinguish between the object and braille text.
-
Make sure there is sufficient space around braille labels. A capitalised word starts with only a dot 6. The area in the braille cell that dots 1, 2 and 3 would normally occupy must stay empty and not have any other objects there so that the reader can identify the character correctly. There should be additional space before the cell so that it is clear there is no more braille to the left.
-
If a diagram needs a key, use abbreviations as they are more recognisable to the reader than numbers. For example on a map 'NS' is a more instictive label for the North Sea than '7'.
-
When using labels it is helpful to avoid annotation lines which can add unnecessary complication to the image.
-
Braille labels should always be oriented in away that the reader can read then easily from left to right. So avoid rotated braille labels.