如何让 OpenGL 在 pygame 中绘制非显示表面？

Question

我正在尝试制作一款看起来像复古 space 射击游戏的游戏，其中的线条是 3d 线框。为了在 Python 中实现 3D，我使用 pygame 作为 window 和 PyOpenGL 来渲染对象。

我想让 OpenGL 渲染到表面（不是显示表面），然后通过 pygame 放大表面并将其渲染到显示表面。这有望在适合在现代屏幕上工作的同时提供低分辨率的效果 window。

阻止我这样做的是 OpenGL 渲染到显示表面，我找不到任何允许我更改它绘制到的表面的选项。

所以过程应该是：OpenGL 渲染到小表面，pygame 缩放表面并将其绘制到显示屏，重复。

这是我当前的代码：

def main():
    pygame.init()
    display = (500,500)
    pygame.display.set_mode(display, DOUBLEBUF|OPENGL) # Create display window

    gluPerspective(70, (display[0]/display[1]), 0.1, 50.0) # Setup view

    glTranslatef(0.0,0.0, -5) # Set view position

    while True:
        for event in pygame.event.get():
            if event.type == pygame.QUIT: # If X is clicked
                pygame.quit() # Close
                quit()
        glRotatef(1, 3, 1, 1) # Rotates view
        glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT) # Clears the screen
        Cube() # Renders the cube onto the screen
        pygame.display.flip() # Updates the display
        pygame.time.wait(10)

main()

我已经尝试创建一个与显示器具有完全相同设置的表面，但 OpenGL 仍然不会将其渲染到该表面。

Answer 1

您必须创建一个 Framebuffer Object (before the main loop) with a resoultion smaller than the window resolution. See also Framebuffer Object Extension Examples:

fb_size = [50, 50]

depth_buffer_obj = glGenRenderbuffers(1)
glBindRenderbuffer(GL_RENDERBUFFER, depth_buffer_obj)
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, fb_size[0], fb_size[1])

color_buffer_obj = glGenRenderbuffers(1)
glBindRenderbuffer(GL_RENDERBUFFER, color_buffer_obj)
glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA, fb_size[0], fb_size[1])

fb_obj = glGenFramebuffers(1)
glBindFramebuffer(GL_FRAMEBUFFER, fb_obj)
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth_buffer_obj)
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, color_buffer_obj)

status = glCheckFramebufferStatus(GL_FRAMEBUFFER)
if status != GL_FRAMEBUFFER_COMPLETE:
    print("incomplete framebuffer object")
glBindFramebuffer(GL_FRAMEBUFFER, 0)

将视口的大小设置为帧缓冲区的大小，清除帧缓冲区并将立方体渲染到 Framebuffer:

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit() 
            quit()

    glBindFramebuffer(GL_FRAMEBUFFER, fb_obj)
    glViewport (0, 0, fb_size[0], fb_size[1])
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)

    glRotatef(1, 3, 1, 1)
    Cube()

将视口大小设置为 window 的大小，并使用 glBlitFramebuffer 和过滤器参数 GL_NEAREST 从中复制像素命名的帧缓冲区对象到默认的帧缓冲区。请注意，没有必要清除默认帧缓冲区，因为它已被完全覆盖：

while True:

    # .....

    glBindFramebuffer(GL_READ_FRAMEBUFFER, fb_obj)
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0)
    glViewport(0, 0, 500, 500)

    glBlitFramebuffer(
        0, 0, fb_size[0], fb_size[1],
        0, 0, 500, 500,
        GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT,
        GL_NEAREST)

    pygame.display.flip()
    pygame.time.wait(10)

请注意，glBindFramebuffer(GL_READ_FRAMEBUFFER, fb_obj) 行不是必需的，因为此时 fb_obj 绑定用于读取和绘制。

如果您的系统不支持 glBlitFramebuffer，您可以创建一个带有附加到其颜色平面的纹理的帧缓冲区：

fb_size = [50, 50]

depth_buffer_obj = glGenRenderbuffers(1)
glBindRenderbuffer(GL_RENDERBUFFER, depth_buffer_obj)
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, fb_size[0], fb_size[1])

#color_buffer_obj = glGenRenderbuffers(1)
#glBindRenderbuffer(GL_RENDERBUFFER, color_buffer_obj)
#glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA, fb_size[0], fb_size[1])

color_tex_obj = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, color_tex_obj)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, fb_size[0], fb_size[1], 0, GL_RGBA, GL_UNSIGNED_BYTE, None)

fb_obj = glGenFramebuffers(1)
glBindFramebuffer(GL_FRAMEBUFFER, fb_obj)
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth_buffer_obj)
#glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, color_buffer_obj)
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, color_tex_obj, 0)

status = glCheckFramebufferStatus(GL_FRAMEBUFFER)
if status != GL_FRAMEBUFFER_COMPLETE:
    print("incomplete framebuffer object")
glBindFramebuffer(GL_FRAMEBUFFER, 0)
glBindTexture(GL_TEXTURE_2D, 0)

渲染到帧缓冲区并在整个 window 上绘制一个带有纹理的四边形到默认帧缓冲区：

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit() 
            quit()

    glBindFramebuffer(GL_FRAMEBUFFER, fb_obj)
    glViewport (0, 0, fb_size[0], fb_size[1])
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)

    glRotatef(1, 3, 1, 1)
    gluSphere(gluNewQuadric( ), 2.0, 32, 32)

    glBindFramebuffer(GL_FRAMEBUFFER, 0)
    glViewport(0, 0, 500, 500)
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)

    glMatrixMode(GL_PROJECTION)
    glPushMatrix()
    glLoadIdentity()
    glMatrixMode(GL_MODELVIEW)
    glPushMatrix()
    glLoadIdentity()

    #glBlitFramebuffer(
    #    0, 0, fb_size[0], fb_size[1],
    #    0, 0, 500, 500,
    #    GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT,
    #    GL_NEAREST)

    glEnable(GL_TEXTURE_2D)
    glBindTexture(GL_TEXTURE_2D, color_tex_obj)
    glBegin(GL_TRIANGLE_FAN)
    glTexCoord2f(0,0)
    glVertex2f(-1,-1)
    glTexCoord2f(1,0)
    glVertex2f(1,-1)
    glTexCoord2f(1,1)
    glVertex2f(1,1)
    glTexCoord2f(0,1)
    glVertex2f(-1,1)
    glEnd()
    glDisable(GL_TEXTURE_2D)

    glMatrixMode(GL_PROJECTION)
    glPopMatrix()
    glMatrixMode(GL_MODELVIEW)
    glPopMatrix()

    pygame.display.flip()
    pygame.time.wait(10)

如何让 OpenGL 在 pygame 中绘制非显示表面？

How do I make OpenGL draw do a non-display surface in pygame?

python

opengl

pygame

pyopengl