CODEWITHSUNDEEP
racketkeyevent
user22638798
user22638798

Reputation: 9

Rotating an Animated Image on Key

I am having a problem with rotating an animated image on key. I do not quite understand big-bang functions and have lost hope.

This is my code:

(require 2htdp/image)
(require 2htdp/universe)

;; Found the png of the rocketship online. Couldn't find anything smaller so, we adjust the background to not make it look gigantic.
(define SHIP "rocketship png")

;; Restricts the landing to the bottom of the scene's boundary
(define (create-rocket-scene height)
    (place-image SHIP 150 (min height 550) (rectangle 300 600 'solid  'black)))

(define (key-press w ke)
    (cond
    \[(key=? ke "u") (make-posn 0)\]
    \[(key=? ke "d") (make-posn (rotate 180))\]
    \[else w\]))

(big-bang 0
    \[to-draw render\]
    \[on-key key-press\])

This results in numerous errors. I need to have the rocketship descend down the scene and land (this is all correct). However, once I add in the on-key and big-bang functions to allow me to rotate the image 180 degrees, it does not work. I am very frustrated. Please advise.

Upvotes: 0

Views: 81

Answers (1)

soegaard
soegaard

Reputation: 31145

In order to draw a rocket both in the correct position and the correct orientation (rotation), you need to two pieces of information: 1) the position of the rocket and 2) the orientation of the rocket.

Currently your world consists of the position only, so you are you using a posn structure that holds an x and an y value. What's missing is a somewhere to store the orientation.

One option is:

(define-struct world [x y r])

Here x and y works as before. The r is the angle of the rocket measured in radians.

Another option is:

(define-struct world [p r])

Here p will hold a position in form of a posn structure and r will be the angle of the rocket in radians.

Upvotes: 0

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