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Introduction to Computer Graphics – CGS-1586C

Spring Quarter 2011Instructor: Amanda DickinsonTues/Thurs from 6:00PM to 7:50 PM

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Overview for Today

Wikispaces Project 1 Critiques Pathfinder Live Tracing Masking Pen Tool Class Exercise Project 2 Homework

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Wikispaces

I finally got around to creating one It will have files and other important

stuff there

http://cgs1586c.wikispaces.com/

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Project 1 Critiques

We will be going over Project 1 and having a class critique of each other’s work.

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Pathfinder

We’ve used this tool a few times already.

Here is a closer look at what the buttons actually do.

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Pathfinder

The pathfinder doesn’t actually find paths, it creates new ones from existing shapes.

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Pathfinder

Add/Unite - Combines all the selected objects and merges them into a singe shape. If the objects are different colors, the merged shape takes on the attributes of the top-most object.

Subtract/Minus Front - Uses the top object(s) as a sort of “cookie cutter” to subtract their shapes from the bottom object.

Intersect - Deletes everything that does not overlap, and combines the rest into a single shape.

Exclude - The opposite of Intersect. Instead of getting rid of everything that isn’t overlapping, it gets rid of everything that does overlap. The resulting shapes become a compound path.

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Pathfinder With more than 2 objects:

Add - The resulting shape will take on the color attributes of the top-most object.

Subtract - The front-most objects will be cut out from the back-most object.

Intersect - Only the areas in which all the objects overlap will remain.

Exclude - When an even number of objects overlap, the overlap is cut out. When an odd number of objects overlap, the overlap becomes filled. And again, the resulting shape will take on the color attributes of the top-most object.

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Pathfinder Divide: Probably the most often used, Divide cuts

the artwork into separate pieces wherever shapes overlap. Color attributes of the original shapes are not changed. After Dividing, you can use the Direct Selection or Group Selection tool to move the resulting pieces independently. You can also ungroup the shapes and move them with the Selection tool.

Trim: Removes the part(s) of the objects that are overlapping or hidden. If the objects are stroked, Trim removes the strokes. It does not merge objects with the same color attributes.

Merge: Depending on the shapes you start with, you might think that Merge does exactly what Trim does. Merge has one exception, however. It does merge overlapping objects filled with the same color (regardless of the stacking order).

Crop: Uses the topmost object to crop away everything else. Think of it as an inverse cookie cutter. It also removes strokes.

Outline: This is another Pathfinder that, at first glance, may seem to do nothing. But look closer and you’ll see that it is sort of like Divide, only instead of individual shapes, the result is individual line segments

Minus Back: Does the Opposite of Minus Front/Subtract. Anything overlapping and in back of the frontmost object goes away.

Original Outline

ResultingPaths

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Live Tracing

Remember when I mentioned that Illustrator can change bitmaps/raster to vector?

Bitmap/Raster Vector

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Live Tracing

To change raster pictures to vector: Place a bitmap/raster image on the

artboard using File > Place You can place bmp, jpg, gif, png, tif, or

psd files Choose Object > Live Race > Tracing

Options This gives you options for how many

paths, colors, anchor points, etc Click the Trace button when finished

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Live Tracing

The image will still look like it’s in one piece, to make it editable: Object > Live Trace > Expand Click Trace This converts the image to vector paths

And that’s it! Use Trace Options to experiment with your new vector image.

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Masking

Opacity Masks and Clipping Masks are very powerful and commonly used tools in Illustrator

You can easily reveal or hide artwork without deleting paths

This is good for faster and easier revisions and edits of your project

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Masking

Clipping Paths are Binary (on or off) operations applied against all paths/objects within a layer. This can even include sub-layers with separately defined Clipping Paths.

Opacity Masks are gray-scale Maps applied against individual paths/objects only. The only exception is that an Opacity Mask may be applied against a set of objects if they are Grouped.

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Masking

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Masking

Let’s talk about Clipping Paths These are good for Cropping pieces of

artwork to make new shapes or keep it inside certain dimensions

So how do we make one?

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Masking Create the object you want to use as the mask. This

object is called the clipping path. Only vector objects can be clipping paths.

Move the clipping path and the objects you want to mask into a layer or group.

Either: In the Layers panel, make sure that the masking object

is at the top of the group or layer, and then click the name of the layer or group.

Click the Make/Release Clipping Masks button at the bottom of the Layers panel or select Make Clipping Mask from the Layers panel menu.

OR Select your path object first, then the object you want to mask

Choose Object > Clipping Mask > Make

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Masking

Clipping Path

BackgroundObject

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Masking

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Masking

Ta-da!

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Masking

Ok, what about opacity masks?

Start with an object in the front of a background (to see the mask work)

(Make sure to lock your background in the layer panel)

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Masking

Copy and paste a new object on top of the first object (or use offset path)

Fill this new object with a gradient

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Masking

Select BOTH shapes Go to transparency pallete and click

the upper right settings icon Select “Make Opacity Mask”

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Masking

There you have it. Change the gradient, change the mask. You must use black and white gradients

for this to work To get rid of the mask, select “release

opacity mask” in the transparency pallete options

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Pen Tool

Ever wish you had more control over your lines and curves?

Use the pen tool!

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Pen Tool

Click and hold down the pen tool icon to reveal many more functions for the pen tool

Main tool: Pen Tool - Click on artboard to create paths with straight segments, click and drag to create curved paths

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Pen Tool

Add anchor point tool : Click on a path segment to add anchor points.

Delete anchor point tool : Click on anchor point to remove from path.

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Pen Tool

Convert anchor point : Click on an anchor point and drag to create bezier handles where there were none, click on an anchor point with handles to a remove them.

Scissors : Not part of the Pen tool group, but definitely associated with it. Click on a path segment to divide into two paths.

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Pen Tool

Keyboard Shortcuts Select Pen tool (P) Select Add anchor point tool (+) Select Delete anchor point tool (-) Select Convert anchor point tool (Shift

+ C) Select Scissors tool (C)

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Pen Tool

Ah my cursor changed, what does it mean??

(TIP - Use capslock to toggle between pointer and crosshair)

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Pen Tool Hints and Tips

Drag handles from the first anchor point when beginning a curved path.

Drag your handles around just one third of the curve you’re creating for a smooth path

Position anchor points on a curve where the paths begin to change direction, not in the middle of it’s curve.

Be sparing with your use of anchor points, fewer points = neater path.

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Class Exercise

It’s one thing talking about the pen tool, let’s try a practice run.

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Project 2

You will be creating a T-Shirt design in Illustrator Follow the limitations and directions of the

project Save the files in your course files folder for

grading I will be handing out detailed instructions in

class

Due May 3rd at the beginning of class.

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Homework

Read Chapter 7 in Digital Foundations before next Tuesday. We will be starting Photoshop.

Finish and turn in Project 2 at the beginning of next Tuesday’s class.