Once you rotate a surface it will not be the same size as the original object if the source is not a square, so collision detection would actually probably be harder than detecting if a line intersected a rectangle or a circle.
-----Original Message----- From: "tom arnall" <kloro2...@gmail.com> Sent: 8/25/2015 6:25 PM To: "pygame-users@seul.org" <pygame-users@seul.org> Subject: Re: [pygame] possible to get rid of ghost image after rotating aline? I spoke too soon. the use of draw.line() won't work for my application. I need to be able to easily detect when the line touches a moving target. Therefore AFIK I need the line to be either a surface or drawn on a surface, so I can use the surface Rect to check when the line collides with a target. I can't see a way to use a line created by draw.line() to do this. I also would like the line to behave like the example you referenced, i.e. to rotate around one of its endpoints, not its center, but this is a nice-to-have feature; it would also work if the line surface just rotated around its center. Tom Arnall ..... “I have no special talents, only a passionate and stubborn curiosity.” Albert Einstein On 8/25/15, Paul Vincent Craven <p...@cravenfamily.com> wrote: > I'm not sure why you are creating a new surface everytime. Or why you > create one at all? > > Is this similar to what you are looking for? > > http://programarcadegames.com/python_examples/f.php?file=radar_sweep.py > > Paul Vincent Craven > > On Tue, Aug 25, 2015 at 3:57 PM, tom arnall <kloro2...@gmail.com> wrote: > >> I want to rotate a line around a point. The code that follows does >> this, BUT when it draws a line, it leaves next to the line its ghost. >> Is this a problem with pygame, or is there a change I can make in the >> code which will make the problem go away? >> >> >> import pygame, sys >> from pygame.locals import * >> import time >> >> pygame.init() >> >> #create a surface that will be seen by the user >> screen = pygame.display.set_mode((400, 400)) >> >> #create a varible for degrees pf rotation >> degree = 0 >> while True: >> >> for event in pygame.event.get(): >> # quit the game if escape is pressed >> if event.type == QUIT: >> sys.exit() >> elif event.type == KEYDOWN and\ >> event.key == K_ESCAPE: >> sys.exit() >> >> #clear screen at the start of every frame >> screen.fill((40, 40, 40)) >> >> #create new surface with white BG >> surf = pygame.Surface((1000, 5)) >> surf.fill((255, 255, 255)) >> #set a color key for blitting >> surf.set_colorkey((255, 0, 0)) >> >> >> ##ORIGINAL UNCHANGED >> #where will the static image be placed: >> where = (0,200) >> >> #draw surf to screen and catch the rect that blit returns >> blittedRect = screen.blit(surf, where) >> >> ##ROTATED >> #get center of surf for later >> oldCenter = blittedRect.center >> >> #rotate surf by DEGREE amount degrees >> rotatedSurf = pygame.transform.rotate(surf, degree) >> >> #get the rect of the rotated surf and set it's center to the >> oldCenter >> rotRect = rotatedSurf.get_rect() >> rotRect.center = oldCenter >> >> #draw rotatedSurf with the corrected rect so it gets put in the >> proper >> spot >> screen.blit(rotatedSurf, rotRect) >> >> #change the degree of rotation >> degree += 5 >> if degree > 360: >> degree = 0 >> >> #show the screen surface >> pygame.display.flip() >> >> #wait 60 ms until loop restart >> pygame.time.wait(60) >> >
