Re: [pygame] Masking Test: Simulated Lighting (Follow-Up)

[Kamilche <kamilche@xxxxxxxxxxxx>]

Kris Schnee wrote:
> But a problem appeared in trying to make the process more efficient, by 
> drawing a lightmask on its own, once, then each blitting it onto the 
> black mask, then blitting the black mask onto the screen. Doing it that 
> way would be better for complex, gradient lights such as the big one 
> seen in my previous code. That is, you'd make a (radius*2,radius*2) 
> surface that's black with a gradually-shaded circle of translucency, 
> once, then blit it onto solid black each frame. But when I tried that,
> Pygame took me too literally. 

Try the following code. It uses a gradient light.

import pygame

SCREENSIZE = [800, 600]
LIGHTSIZE = 400
NIGHTCOLOR = [0, 0, 0, 200]

def CreateLight():
    gradient = pygame.Surface([LIGHTSIZE, LIGHTSIZE], 0, 8)
    gradient.set_palette([[x, x, x] for x in range(256)])
    a = NIGHTCOLOR[3]
    gradient.fill((a, a, a))
    r = LIGHTSIZE/2
    for i in range(r):
        c = (a * (r-i))/r
        pygame.draw.circle(gradient, [c, c, c], [r, r], r-i)
        c -= 1
    return gradient

def CreateBackground():
    bg = pygame.Surface(SCREENSIZE, pygame.SRCALPHA, 32).convert_alpha()
    bg.fill((0, 0, 128, 255))
    bg.fill((255, 0, 0, 255), (50, 50, 100, 100))
    return bg

def CreateNight():
    pic = pygame.Surface(SCREENSIZE, pygame.SRCALPHA, 32).convert_alpha()
    pic.fill(NIGHTCOLOR)
    return pic

def CreateAlpha():
    pic = pygame.Surface(SCREENSIZE, 0, 8)
    pic.set_palette([[x, x, x] for x in range(256)])
    a = NIGHTCOLOR[3]
    pic.fill([a, a, a])
    return pic

def RefreshNight(night, alpha, light, x, y):
    a = NIGHTCOLOR[3]
    alpha.fill([a, a, a])
    r = LIGHTSIZE/2
    alpha.blit(light, [x-r, y-r])
    pygame.surfarray.pixels_alpha(night)[:, :] = 
pygame.surfarray.pixels2d(alpha)

def main():
    pygame.init()
    screen = pygame.display.set_mode(SCREENSIZE, 0, 32)
    bg = CreateBackground()
    circle = CreateLight()
    night = CreateNight()
    alpha = CreateAlpha()
    done = 0
    x, y = 400, 300
    while not done:
        RefreshNight(night, alpha, circle, x, y)
        screen.blit(bg, (0, 0))
        screen.blit(night, (0, 0))
        pygame.display.flip()
        pygame.event.pump()
        for event in pygame.event.get():
            if (event.type == pygame.QUIT) or \
               (event.type == pygame.KEYDOWN and event.key == 
pygame.K_ESCAPE):
                done = True
                break
            elif event.type == pygame.MOUSEMOTION:
                x, y = event.pos
    pygame.quit()

main()