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Published byLance Stickels Modified about 1 year ago

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This terms course Last term we both worked on learning 2 things –Processing –The concepts of graphics etc. This term will focus more on the basic concepts –Graphics, 2D and 3D –Sound The course will go more into the maths and theory

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Aims Understand Vectors –Position/displacement, direction, length Use Vectors in Processing programs –in 2D and 3D Understand Transforms Use Translations and Scales Use pushMatrix and popMatrix

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Vectors x and y are the coordinates of points In maths we can group them together as a single object (x,y) This is called a vector

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Vectors A vector can represent 2 things

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Vectors A vector can represent 2 things A position on the screen (A position vector) (x,y)

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Vectors A vector can represent 2 things A displacement between two points (A displacement vector) (x,y)

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Vectors A position vector is really a displacement from the origin (0,0) (x,y)

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Vectors Position Vectors –drawing shapes –positions of object Displacement Vectors –Velocities, movements

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Maths on Vectors You can do maths on vectors Normally you do each operation on each element separately It normally help to think about vectors as displacement vectors

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Vector addition add vectors (x1, y1) + (x2, y2) = (x1+x2, y1+y2) do one displacement after another (x1,y1) (x2,y2) (x1+x2,y1+y2)

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Vector subtract subtract vector (x1, y1) - (x2, y2) = (x1-x2, y1-y2) The displacement of one position relative to another Very useful (x1,y1) (x2,y2) (x2+x1,y2+y1)

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Length of a vector you can calculate the length (magnitude) of a vector using Pythagoras' theorem l 2 = x 2 + y 2 l = sqrt(x 2 + y 2 ) x y l

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Length and direction You can think of a vector as having a length and a direction The direction is a vector that is in the same direction but of length 1 Calculate it by dividing each component of a vector by the length –(x/sqrt(x 2 + y 2 ), y/sqrt(x 2 + y 2 )) Called normalising

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Length and direction Very useful to be able to think about both Length –know the distance between two objects –know how fast an something is moving (e.g. for setting a max speed) Direction –Move at a constant speed in a direction given by two points –Turn an object to face the direction its moving in

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Vectors in 3D We can also do the same things in 3D An extra item, z, represents depth pass in an extra parameter OPENGL or P3D to size The maths works the same –length is sqrt(x 2 + y 2 + z 2 )

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Vectors in Processing dist() gives the distance between two points –length of the displacement between them

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Vectors in Processing dist() gives the distance between two points –length of the displacement between them PVector is a class for representing vectors Its new to the latest version of Processing

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Exercises Rewrite my last example to use PVector make it work in 3D

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Aims Understand Vectors –Position/displacement, direction, length Use Vectors in Processing programs –in 2D and 3D Understand Transforms Use Translations and Scales Use pushMatrix and popMatrix

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Transformations Translate Rotate Scale

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Transformations Transformations act on the whole processing screen

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Transformations Translate moves the whole coordinate system by a x and y direction

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Transformations Translate moves the whole coordinate system by a x and y direction

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Transformations Anything before the translate call is draw normally

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Transformations Anything before the translate call is draw normally Anything after the call is drawn relative to the new transformed coordinate system

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Transformations Scale will change the size of the coordinates relatives to the origin (0, 0)

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Transformations Scale will change the size of the coordinates relatives to the origin (0, 0)

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Transformations The order of transforms is very important Changing the order changes the result

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Transformations A transform applies to all the code that happens after it

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Transformations A transform applies to all the code that happens after it That means it also applies to other transforms

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Transformations A transform applies to all the code that happens after it Translate() Translates everything twice

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Transformations A transform applies to all the code that happens after it Translate() Translates everything twice

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Transformations A transform applies to all the code that happens after it A translate followed by a rotate means “apply the translate to the result of rotate”

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Transformations The order of transforms is very important Translate() Rotate() Means translate the result of rotating

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Transformations The order of transforms is very important Translate() Rotate() Means translate the result of rotating

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Transformations The order of transforms is very important Translate() Rotate() Means translate the result of rotating

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Transformations The order of transforms is very important Rotate() Translate() Means rotate the result of translating

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Transformations The order of transforms is very important Rotate() Translate() Means rotate the result of translating

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Transformations The order of transforms is very important Rotate() Translate() Means rotate the result of translating

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Transformations This is the opposite order you would expect Translate() Rotate() Is a bit like rotating then translating

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Order of transforms The normal best order is Translate Rotate Scale This means that an object is scaled the same why no matter how it is rotated It is translated the same way no matter how it is rotated

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Order of transforms Rotate Translate

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Order of transforms Rotate Translate

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Order of transforms Rotate Translate Doesn’t end up at the end point of translating

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Order of transforms Translate Rotate

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Order of transforms Translate Rotate

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Order of transforms Translate Rotate Rotates about its centre –if you use rectMode(CENTER) Translates to the correct position

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Order of transforms Similarly if you scale an object differently along x and y and as well as rotating the order matters If you do –Scale() –Rotate() The result is no longer a rectangle (skewed) (see program)

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Multiple transforms But what if we want to draw more than one thing?

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Multiple transforms But what if we want to draw more than one thing? If we transform the first one then the second, the first transform will apply to the second as well

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Transform Matrices A transform is represented internally as a matrix A 3D array of number The details of how doesn’t matter at the moment

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Transform Matrices Up to now we have only had 1 matrix All transforms are combined together into this matrix To draw more than one object we need more than one matrix

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Transform Matrices Up to now we have only had 1 matrix All transforms are combined together into this matrix To draw more than one object we need more than one matrix Multiple matrices are stored in a “Stack”

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Stacks A Stack is like a stack of paper

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Stacks A Stack is like a stack of paper You can put things on it –“Push” it on a stack

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Stacks A Stack is like a stack of paper You can put things on it And take things off –“Pop” it off the stack

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Stacks A Stack is like a stack of paper You can put things on it And take things off –“Pop” it off the stack 1 2 3

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Stacks The last thing to be put on is the first to be taken off Last in, first out 1 2 3

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Matrix Stacks Storing matrices as a stack means that the most recent transforms are the ones you remove first Generally what you want Global transforms that affect the whole picture are at the bottom Transforms that only affect a single object at the top

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Pushing and Popping Matrices PushMatrix() creates a new matrix and puts it on the top of the stack You can then do any transforms you like PopMatrix() will then remove the matrix from the stack i.e. it will remove all the transforms you have done

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Multiple Objects For multiple objects: –PushMatrix() before drawing each object –Do all the transforms for that object –PopMatrix() to get rid of the transforms before moving on to the next matrix

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Transforms in 3D Translation works exactly the same in 3D need an x,y and z for the translation vector rotation is more complex: next lecture

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Exercises Draw a rectangle, rotating, translating and scaling it Draw multiple rectangles in multiple positions using PushMatrix and PopMatrix Do the same with boxes in 3D

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