[[http://quickdocs.org/sketch/][file:http://quickdocs.org/badge/sketch.svg]]
Sketch is a Common Lisp environment for the creation of electronic art, visual design, game prototyping, game making, computer graphics, exploration of human-computer interaction and more. It is inspired by [[https://processing.org][Processing Language]] and shares some of the API.
[[http://i.imgur.com/MNZUwz8.png]]
** Installation
Sketch is available through [[https://www.quicklisp.org/beta/][Quicklisp]], Common Lisp's de facto package manager. From your REPL, run:
(ql:quickload :sketch)
To make Sketch run correctly, however, a few requirements must be met.
* Requirements ** Common Lisp Implementation Sketch should be compatible with all major Common Lisp implementations and all major operating systems - more specifically, all CL implementations and operating systems that [[https://github.com/lispgames/cl-sdl2][cl-sdl2]] runs on. Incompatibility with any of these is considered a bug.
Sketch is known to work with:
Workarounds, or extra steps, may be required on some systems:
Sketch is known to not work with:
If you test Sketch on other systems, please send a pull request to include your results.
** Foreign dependencies *** SDL2 SDL2 is currently Sketch's only backend. It is a C library which you will need to download manually from [[https://www.libsdl.org][libsdl webpage]]. Select the release compatible with your operating system, or compile from the source code.
***** SDL2 Image & SDL2 TTF For loading image and font files, Sketch relies on SDL2 Image and SDL2 TTF, respectively, both part of the SDL project.
***** libffi Some users have reported that [[https://sourceware.org/libffi/][libffi]] needed to be installed to make Sketch work.
***** OpenGL Sketch requires graphics hardware and drivers with support for GL version 3.3.
**** Installing and running Sketch on Windows Sketch works on both CCL and SBCL, but installing all prerequisites might not be as straightforward as it is on the other platforms.
***** Libraries Download SDL2, SDL2_IMAGE and SDL2_TTF dlls from [[https://www.libsdl.org][libsdl webpage]] and copy them somewhere Windows can find them - =\Windows\System32= will work. When copying SDL2_TTF, make sure to copy all of the dlls provided in the archive, and not just the TTF one.
Now you will need to get a libffi dll. One of the ways of doing this is compiling from the source, but for a quick and easy solution, you can just find a trusted source and use their version. For example, if you are using Emacs on Windows, you can find =libffi-6.dll= in =emacs\bin=. Copy it to the same directory you copied sdl2 dlls to earlier.
***** GCC To bootstrap cffi-libffi, you are going to need a C compiler, more specifically the one from the GNU Compiler Collection. Also, libffi headers and pkg-config are needed. Luckily, you can get all these things (and more) with MSYS2. Go to [[https://msys2.github.io]] and follow the instructions for installing the 64bit version.
From its console, install gcc, libffi headers and pkg-config by running =pacman -S gcc libffi libffi-devel pkg-config=.
***** Environment variables From the Control Panel, open System properties, go to the Advanced tab, and click "Environment Variables..." - or click the Start button, start typing "environment" and select "Edit the system environment variables".
Double click "Path" from the list of System variables and make sure that both your lisp implementation's path (something like =C:\Program Files\Steel Bank Common Lisp\1.3.6\=) and MSYS path (probably =C:\msys64\usr\bin=) are listed. If not, click "New" and add them now.
If you needed to change anything here, restart the computer now.
***** SLIME If you are using SLIME, you won't be able to load or run Sketch if you start SWANK from emacs (by running =M-x slime=). Instead, you should open the Command Prompt (the regular one, not MSYS), start your lisp and eval =(ql:quickload :swank)= =(swank:create-server)=. From Emacs, type =M-x slime-connect=, and finally, press enter twice (for localhost and port 4005).
If you did everything correctly, you should be able to =(ql:quickload :sketch)= and move on to the tutorial.
*** Running provided examples To get a feel for what Sketch can do, and also to make sure that everything has been installed correctly, run the examples as follows.
CL-USER> (ql:quickload :sketch-examples) CL-USER> (make-instance 'sketch-examples:hello-world) CL-USER> (make-instance 'sketch-examples:sinewave) CL-USER> (make-instance 'sketch-examples:brownian) CL-USER> (make-instance 'sketch-examples:life) ; Click to toggle cells, ; any key to toggle iteration CL-USER> (make-instance 'sketch-examples:input) CL-USER> (make-instance 'sketch-examples:stars)
*** Running example code from this page In all the following examples, we're going to assume that Sketch is loaded with =(ql:quickload :sketch)=, and that we're in package =:TUTORIAL=, which is set to use =:SKETCH=.
CL-USER> (ql:quickload :sketch) CL-USER> (defpackage :tutorial (:use :cl :sketch)) CL-USER> (in-package :tutorial) TUTORIAL> ;; ready
** Tutorial Defining sketches is done with the =defsketch= macro, which is essentially a wrapper for =defclass=.
(defsketch tutorial ()) (make-instance 'tutorial)
If all goes well, this should give you an unremarkable gray window. From now on, assuming you're using Emacs + SLIME, or a similarly capable environment, you can just re-evaluate =(defsketch tutorial ()
*** Shapes Let's draw something! Drawing code goes inside the body of =defsketch=.
=(rect x y w h)= draws a rectangle where =x= and =y= specify the top-left corner of the rectangle, and =w= and =h= are the width and height. By default, the origin (0, 0) is at the top-left corner of the drawing area, and the positive y direction is facing down.
(defsketch tutorial () (rect 100 100 200 200))
(defsketch tutorial () (dotimes (i 10) (rect 0 ( i 40) ( (+ i 1) 40) 40)))
Something to note: drawing code doesn't need to go into a special function or method, or be explicitly binded to a sketch. =defsketch= is defined as =(defsketch sketch-name bindings &body body)=: that body, and any functions it calls to, is your drawing code. We will get to =bindings= later.
Circles and ellipses are drawn with =(circle x y r)= and =(ellipse cx cy rx ry)=:
(defsketch tutorial () (circle 300 100 50) (ellipse 200 200 100 50))
Lines with =(line x1 y1 x2 y2)=:
(defsketch tutorial () (line 0 0 400 400) (line 400 0 0 400))
Lines with an arbitrary number of segments with =polyline=:
(defsketch tutorial () (polyline 100 100 200 150 300 100 200 200 100 100))
Arbitrary polygons can be drawn using =(polygon x1 y1 x2 y2 ...)=, the winding rule (how the "inside parts" and "outside parts" are determined) is specified as a pen property (pens will be described in more detail later) and can be one of =(:odd :nonzero :positive :negative :abs-geq-two)=. By default, it's =:nonzero=.
(defsketch tutorial () (with-pen (make-pen :fill +blue+ :winding-rule :odd) (polygon 100 100 200 150 300 100 200 200)))
To draw a regular polygon with =n= sides, call =(ngon n cx cy rx ry &optional (angle 0))=; =cx= and =cy= are the coordinates of the center of the shape, while =rx= and =ry= are height of an ellipse that the shape is inscribed inside.
(defsketch tutorial () (dotimes (i 4) (ngon (+ i 3) (+ 50 ( i 100)) 200 20 20 ( i 20))))
Bezier curves with 4 control points are drawn with =(bezier x1 y1 bx1 by1 bx2 by2 x2 y2)=; =x1=, =y1=, =x2= and =y2= determine the start and end points.
(defsketch tutorial () (bezier 0 400 100 100 300 100 400 400))
The resolution of a curve can be controlled with the pen property =:curve-steps=, for example:
(defsketch tutorial () (with-pen (make-pen :curve-steps 4 :stroke +white+) (bezier 0 400 100 100 300 100 400 400)))
*** Configuring your sketch The first form in =defsketch= after the name of your sketch, and before the body, is a list of bindings that will be available in the sketch body. This is also where a number of configuration options can be set:
(defsketch tutorial ((radius 10) (resizable t) (width 200)) (circle (/ width 2) (/ radius 2) radius))
*** Colors In the previous examples, you may have noticed how to draw a shape with a fill color. Let's now explore the color capabilities of Sketch in more detail. To draw a yellow background:
(defsketch tutorial () (background +yellow+))
**** Predefined colors There are constants for commonly used colors: =+RED+=, =+GREEN+=, =+BLUE+=, =+YELLOW+=, =+MAGENTA+=, =+CYAN+=, =+ORANGE+= =+WHITE+=, and =+BLACK+=.
**** RGB, HSB, GRAY You can create other colors using =(rgb red green blue &optional (alpha 1.0))=, =(hsb hue saturation brightness &optional (alpha 1.0))= or =(gray amount &optional (alpha 1.0))=. The arguments to these functions are values from 0 to 1. =(gray amount &optional (alpha 1.0))= is really just a convenient alias for =(rgb amount amount amount &optional (alpha 1.0))=.
More information:
/This might be a good place to note that function names in Sketch use the American English spellings, like "gray" and "color". It's just a choice that needed to be made, in pursuit of uniformity and good style./
For a lighter yellow:
(defsketch tutorial () (background (rgb 1 1 0.5)))
All color functions have an additional =ALPHA= parameter that determines the transparency.
**** RGB-255, HSB-360, GRAY-255 Sometimes it's easier to think about color values in non-normalized ranges. That's why Sketch offers =RGB-255=, =HSB-360=, and =GRAY-255=.
This is how these functions map to their normalized variants.
| (rgb-255 r g b a) | (rgb (/ r 255) (/ g 255) (/ b 255) (/ a 255)) | | (hsb-360 h s b a) | (hsb (/ h 360) (/ s 100) (/ b 100) (/ a 255)) | | (gray-255 g a) | (gray (/ g 255) (/ a 255)) |
=HSB-360= uses different ranges, because hue is represented in degrees (0-360), and saturation and brightness are represented as percentages (0-100).
**** HEX-TO-COLOR If you are used to working with colors in hex, like in CSS, you can use =(hex-to-color string)=, where =STRING= is the color in one of the following formats: "4bc", "#4bc", "4bcdef", or "#4bcdef".
**** Generating colors If you don't care about fiddling with the exact values, but still need different colors, you can use one of the following functions.
***** =(lerp-color (start-color end-color amount &key (mode :hsb)))= Lerp is a shorthand for [[https://en.wikipedia.org/wiki/Linear_interpolation][linear interpolation]]. This function takes the starting color and the ending color, and returns the color between them, which is an =AMOUNT= away from the starting color. When =AMOUNT= equals zero, the returned color equals the starting color, and when =AMOUNT= equals one, the ending color is returned. Amounts between zero and one give colors that are "in-between". These colors are calculated according to the specified =MODE=, which is =:HSB= by default, meaning that the resulting color's hue is between the starting and ending hue, as is the case with its saturation and brightness.
(defsketch lerp-test ((title "lerp-color") (width 400) (height 100)) (dotimes (i 4) (with-pen (make-pen :fill (lerp-color +red+ +yellow+ (/ i 4))) (rect (* i 100) 0 100 100))))
***** =(random-color (&optional (alpha 1.0)))= Returns a random color. You probably don't want to use this, because many of the returned colors will be either too dark, or too light. You do get to choose the =ALPHA= value, though.
(defparameter colors (loop for i below 16 collect (random-color)))
(defsketch random-color-test ((title "random-color") (width 400) (height 100)) (dotimes (x 8) (dotimes (y 2) (with-pen (make-pen :fill (elt colors (+ x ( y 8)))) (rect ( x 50) (* y 50) 50 50)))))
***** =(hash-color (n &optional (alpha 1.0)))= This is probably the function you're looking for, if you just want to create a non-repeating set of colors quickly. It maps all numbers to "interesting" (not too dark, not too light) colors. You can use this for coloring procedurally generated objects, when prototyping and just trying to make things look different quickly, when making palettes, looking for "the right" color, and many other things.
(defsketch hash-color-test ((title "hash-color") (width 400) (height 100)) (dotimes (i 128) (with-pen (make-pen :fill (hash-color i)) (rect (* i (/ 400 128)) 0 (/ 400 128) 100))))
**** Color filters Sometimes you have a color, and would like to transform it in some way. That's what color filters are for.
***** Grayscale To convert colors to grayscale, you can use =color-filter-grayscale=. Two modes of grayscale conversion are implemented:
(defsketch grayscale-test ((title "grayscale") (width 400) (height 300)) (dotimes (i 10) (let ((color (hash-color i))) (with-pen (make-pen :fill (color-filter-grayscale color)) (rect ( i 40) 0 40 100)) (with-pen (make-pen :fill color) (rect ( i 40) 100 40 100)) (with-pen (make-pen :fill (color-filter-grayscale color :average)) (rect (* i 40) 200 40 100)))))
***** Invert To invert a color, use =color-filter-invert=:
(defsketch invert-test ((title "invert") (width 300) (height 300) (i 0)) (background +white+) (incf i 0.01) (let ((color (rgb (abs (sin i)) (abs (cos i)) 0))) (with-pen (make-pen :fill color) (circle 100 150 50)) (with-pen (make-pen :fill (color-filter-invert color)) (circle 200 150 50))))
***** Rotate Rotating a color in Sketch using =color-filter-rotate= sets the value of its red channel to the previous value of the green channel; green to blue, and blue to red. The operation is intended to be used in palette generation, because the rotated colors usually work pretty well together.
(defsketch rotate-test ((title "rotate") (width 300) (height 300) (i 0) (color (rgb 0.2 0.8 1.0))) (background +white+) (incf i 1) (when (zerop (mod i 60)) (setf color (color-filter-rotate color))) (with-pen (make-pen :fill color) (rect 100 100 100 100)))
***** HSB [[https://en.wikipedia.org/wiki/HSL_and_HSV][HSB]] stands for Hue/Saturation/Brightness. You can use =color-filter-hsb= to adjust hue, saturation and brightness of an existing color.
(defsketch hsb-test ((title "hsb") (width 400) (height 300) (color (rgb 0.2 0.5 0.6))) (dotimes (i 4) (with-pen (make-pen :fill (color-filter-hsb color :hue ( 0.1 (+ i 1)))) (rect ( i 100) 0 100 100)) (with-pen (make-pen :fill (color-filter-hsb color :saturation ( 0.1 (+ i 1)))) (rect ( i 100) 100 100 100)) (with-pen (make-pen :fill (color-filter-hsb color :brightness ( 0.1 (+ i 1)))) (rect ( i 100) 200 100 100))))
*** Pens Pens are used to draw shapes. If no pen is specified, the default pen sets =:fill= to white, =:stroke= to black, and =weight= to 1.
***** Creating and Using Pens Say you want to draw a red square and a blue circle. You would need to use two different pens.
(defsketch pen-test ((title "pens")) (with-pen (make-pen :fill +red+) (rect 100 100 100 100)) ; this rect will be red (with-pen (make-pen :fill +blue+) (circle 315 315 50))) ; this rect will be blue
***** Fill/Stroke The squares in the previous example were filled because we specified the =:fill= property in =make-pen=. If we wanted to just draw the outline of the square, we would use =:stroke= like this:
(defsketch outline-square ((title "Outline Square")) (with-pen (make-pen :stroke +red+) (rect 100 100 100 100)))
(defsketch fill-stroke ((title "Fill and Stroke")) (background +white+) (with-pen (make-pen :stroke (rgb .5 0 .6) :fill (rgb 0 .8 .8)) (rect 50 50 100 75) (circle 300 220 100)))
***** Weight We can also change the thickness of the lines and shapes that we draw by changing the pen =:weight=.
(defsketch weight-test ((title "Weight Test")) (dotimes (i 10) (with-pen (make-pen :stroke +white+ :weight (+ i 1)) ; pen weight can't be zero (line 50 ( i 20) 350 ( i 20)))))
**** Curve-steps =:curve-steps= is used to change the smoothness (resolution) of curves like =#'bezier=.
(defsketch curve-test ((title "Curve-steps")) (dotimes (i 99) (with-pen (make-pen :stroke +red+ :curve-steps (+ i 1)) ; as curve-step increases, curve becomes "smoother" (bezier 0 400 100 100 300 100 400 400))))
*** Transforms The transforms =(translate dx dy)=, =(rotate angle &optional (cx 0) (cy 0))= and =(scale sx &optional sy (cx 0) (cy 0))= are available to change the view matrix that is applied to coordinates.
Macros =(with-translate (dx dy) &body body)=, =(with-rotate (angle &optional (cx 0) (cy 0)) &body body)= and =(with-scale (sx &optional sy (cx 0) (cy 0)) &body body)= can be used to restore the view matrix after executing the body.
The current view can also be saved on a stack and restored with =(push-matrix)= and =(pop-matrix)=, which are analogous to =push()= and =pop()= in p5.js. The macro =(with-identity-matrix &body body)= pushes the current view matrix onto the stack, sets the view matrix to the identity matrix, executes =body=, and then pops the view matrix. =(with-current-matrix &body body)= is the same, except it doesn't change the view matrix after pushing it.
In this example, translation and rotation are used to draw a triangle in the centre of the screen, without explicitly defining the coordinates of the vertices.
(defsketch transform-test ((title "Transform test") (width 500) (height 500) (side 100) (y-offset (/ side ( 2 (tan (radians 60)))))) (with-translate (250 250) (loop repeat 3 do (line (- ( 1/2 side)) y-offset (* 1/2 side) y-offset) do (rotate 120))))
This example draws a sequence of increasingly shrinking squares using scaling.
(defsketch transform-test ((width 400) (height 400) (title "Scale test")) (translate 100 100) (dotimes (x 5) (rect 0 0 100 100) (translate 150 0) (scale 1/2)))
*** Text Use =(text text-string x y &optional width height)= to draw text, where =x= and =y= specify the top-left corner of the rectangle containing the text. =width= and =height= control the shape of the text box. There is support for changing the [[https://github.com/vydd/sketch/blob/master/src/font.lisp#L29][font]].
(defsketch text-test ((title "Hello, world!")) (text title 0 0 100))
The font can be specified using =(make-font &key face color size line-height align)= and the =with-font= macro.
(defsketch text-test ((title (format nil "Hello, world!~%Next line")) (with-font (make-font :color +white+ :face (load-resource "/path/to/font.ttf") :size 12 :line-height 1 :align :left) (text title 0 0 100)))
=align= can be =:left=, =:centre= or =:right=, and determines whether the x & y coordinates correspond to the left end, centre, or right end of the text box. =line-height= determines the vertical space given to a line of text, scaled according to the font size, i.e. =:line-height 1= leaves just enough space so that the text on two lines won't overlap.
*** Images First =(load-resource filename ...)= to load the image from a given file, then =(draw image &key x y width height)= to draw the image with its top-left corner at =(x, y)= and with the given =width= and =height=. If not provided, default =(x,y)= is =(0,0)= and =width= & =height= are taken from the image.
(defsketch image-test ((title "Hello, image!") (pic (load-resource "/path/to/img.png"))) (draw pic :x 10 :y 10 :width 200 :height 200))
Note that =load-resource= automatically caches the resource when it is called inside a valid sketch environment (i.e. inside the defsketch's body), so it is not inefficient to call it in every loop. It is important to release resources using =sketch::free-resource=; this is done automatically for resources in the sketch environment when the sketch window is closed. Finally, to avoid caching and to reload the resource every time, the parameter =:force-reload-p= can be passed to =load-resource=.
Images can be cropped using =(crop image x y w h)=, where =x= and =y= indicate the top-left corner of the cropping rectangle (relative to the top-left corner of the image) and =w= and =h= indicate the width & height. Image flipping can be accomplished by using negative =w= and =h= values.
*** Input Input is handled by defining implementations of the methods listed below. Currently, it is not possible to call drawing functions from these methods, though this can be worked around by saving the input somewhere and then doing the drawing from the sketch body, as demonstrated in the examples to follow.
In this example, we draw a new rectangle every time there is a click.
(defsketch input-test ((title "Hello, input") (rectangles nil)) (loop for (x y) in rectangles do (rect x y 50 50))) (defmethod on-click ((window input-test) x y) (with-slots (rectangles) window (push (list x y) rectangles)))
In this example, all keyboard text input is echoed to the screen.
(defsketch text-test ((title "Hello, input") (text-to-write nil)) (loop for s in text-to-write do (text s 0 0 20 20) do (translate 20 0))) (defmethod on-text ((window text-test) text) (with-slots (text-to-write) window (setf text-to-write (nconc text-to-write (list text)))))
Finally, here is an example where a pair of eyes follow the mouse (the pupils are restricted to a rectangle, it would look better if they were restricted to a circle).
(defsketch hover-test ((looking-at (list 0 0)) (cx (/ width 2)) (cy (/ height 2))) (let ((cx-1 (- cx 50)) (cx-2 (+ cx 50)) (mx (car looking-at)) (my (cadr looking-at))) (with-pen (make-pen :fill +white+) (ellipse cx-1 cy 40 80) (ellipse cx-2 cy 40 80)) (with-pen (make-pen :fill +black+) (flet ((move-towards (x1 x2) (let ((diff (- x2 x1))) (+ x1 (if (< (abs diff) 10) diff (* (signum diff) 10)))))) (circle (move-towards cx-1 mx) (move-towards cy my) 10) (circle (move-towards cx-2 mx) (move-towards cy my) 10))))) (defmethod on-hover ((window hover-test) x y) (with-slots (looking-at) window (setf (car looking-at) x (cadr looking-at) y)))
See also: [[https://github.com/vydd/sketch/blob/master/examples/life.lisp][life.lisp]].
*** Setup The generic function =(setup instance &key &allow-other-keys)= is a hook that gets called once on every "restart" of the sketch. That is:
Note that any drawing that takes place within =setup= will be immediately covered by a gray background, unless =(copy-pixels t)= is added to =defsketch=.
Here is an example usage of =setup= from [[https://github.com/vydd/sketch/blob/master/examples/brownian.lisp][brownian.lisp]].
(defmethod setup ((instance brownian) &key &allow-other-keys) (background (gray 1)))
*** Saving a picture =(save-png pathname)= can be called within the body of =defsketch= to save a PNG of the currently running sketch. A keyboard shortcut could be set up to take screenshots, as follows.
(defsketch save-test ((should-save nil) (copy-pixels t)) (rect (random width) (random height) 10 10) (when should-save (setf should-save nil) (save-png "/tmp/my-sketch.png"))) (defmethod on-text ((window save-test) text) (when (string= text "s") (setf (slot-value window 'should-save) t)))
*** Drawing with a canvas =(make-canvas width height)= can be used to create a rectangular grid of pixels. The shape of the grid is defined by =width= and =height=.
=(canvas-paint canvas color x y)= sets the color of a pixel within the grid.
=(canvas-lock canvas)= freezes the appearance of the canvas. Any calls to =(canvas-image canvas)= will show an image of the canvas when =canvas-lock= was last called.
=(canvas-unlock canvas)= allows the image of the canvas to be modified again.
=(draw canvas &key (x 0) (y 0) (width nil) (height nil)= draws the canvas; by default, the original width and height of the canvas are used, but these can be overridden.
Example: [[https://github.com/vydd/sketch/blob/master/examples/stars.lisp][stars.lisp]].
*** Control flow =(stop-loop)= from within a sketch body or within an event handler to disable the drawing loop.
=(start-loop)= to start the drawing loop again.
This can be used, for example, to draw a static sketch and then disable the drawing loop so as to not burn up your CPU. It can also be used to regenerate the sketch with each mouseclick.
Example: [[https://github.com/vydd/sketch/blob/master/examples/control-flow.lisp][control-flow.lisp]].
** Made with Sketch
** Outro For everything else, read the code or ask vydd at #lispgames. Go make something pretty!