用PyOpenGL渲染带纹理的矩形

Question

我正在做一个使用PyOpenGL的项目，现在想要让OpenGL显示一个启动画面。我决定的解决办法是画一个带纹理的2D矩形。不过，不管我怎么做，屏幕上总是黑乎乎的（我想应该是有东西被画出来了，要不然窗口应该是透明的，但这显然不是我想要的效果）。以下是我这个类的相关代码：

class ClassThing:
    def __init__(self):
        self.Splash = True
        glutInit(sys.argv)

    def TexFromPNG(self, filename):
        img = Image.open(filename)
        img_data = numpy.array(list(img.getdata()), numpy.uint8)

        texture = glGenTextures(1)
        glPixelStorei(GL_UNPACK_ALIGNMENT,1)
        glBindTexture(GL_TEXTURE_2D, texture)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, img.size[0], img.size[1], 0, GL_RGB, GL_UNSIGNED_BYTE, img_data)
        return texture

    def run(self):
        glutInitDisplayMode(GLUT_RGBA)

        glutInitWindowSize(256,224)
        self.window = glutCreateWindow("GL")
        glutDisplayFunc(self.draw)

        glClearColor(0,0,0,0)
        glEnable(GL_TEXTURE_2D)
        glEnable(GL_VERTEX_ARRAY)

        self.MainTex = glGenTextures(1)
        self.SplashTex = self.TexFromPNG("Resources/Splash.png")

        glutMainLoop()

    def draw(self):
        glClear(GL_COLOR_BUFFER_BIT)
        glLoadIdentity()
        if self.Splash:
            glBindTexture(GL_TEXTURE_2D, self.SplashTex)
        else:
            glBindTexture(GL_TEXTURE_2D, self.MainTex)

        glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
        glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER)
        Varray = numpy.array([[0,0],[0,256],[224,256],[224,0]],numpy.uint16)
        glVertexPointer(2,GL_SHORT,0,Varray)
        indices = [0,1,2,3]
        glDrawElements(GL_QUADS,1,GL_UNSIGNED_SHORT,indices)

        glFlush()
thing = ClassThing()
thing.run()

正如我所说，这段代码让我看到的只是一个完全黑的屏幕。我感觉可能是我漏掉了某些初始化或开启的步骤，但我不知道还需要开启什么。

另外，听说glVertexPointer这个函数已经过时了，那我该怎么在不使用它的情况下运行glDrawElements呢？有没有类似于纹理生成的顶点生成方法？

Answer 1

你还需要提供纹理坐标，不然OpenGL就不知道怎么把纹理贴到你的四边形上。虽然你可以使用自动生成纹理坐标的方法，但在你的情况下，直接指定坐标会更简单。此外，你还需要设置视口和投影。

class ClassThing:
    def __init__(self):
        self.Splash = True

    def TexFromPNG(self, filename):
        img = Image.open(filename)
        img_data = numpy.array(list(img.getdata()), numpy.uint8)

        texture = glGenTextures(1)
        glPixelStorei(GL_UNPACK_ALIGNMENT,1)
        glBindTexture(GL_TEXTURE_2D, texture)

        # Texture parameters are part of the texture object, so you need to 
        # specify them only once for a given texture object.
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, img.size[0], img.size[1], 0, GL_RGB, GL_UNSIGNED_BYTE, img_data)
        return texture

    def run(self):
        glutInitDisplayMode(GLUT_RGBA)

        glutInitWindowSize(256,224)
        self.window = glutCreateWindow("GL")
        glutReshapeFunc(self.reshape)
        glutDisplayFunc(self.draw)

        self.MainTex = glGenTextures(1)
        self.SplashTex = self.TexFromPNG("Resources/Splash.png")

        glutMainLoop()

    def reshape(self, width, height):
        self.width = width
        self.height = height
        glutPostRedisplay();

    def draw(self):
        glViewport(0, 0, self.width, self.height)

        glClearDepth(1) # just for completeness
        glClearColor(0,0,0,0)
        glClear(GL_COLOR_BUFFER_BIT)

        glMatrixMode(GL_PROJECTION)
        glLoadIdentity()
        glOrtho(0, 1, 0, 1, -1, 1)

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity()

        if self.Splash:
            glBindTexture(GL_TEXTURE_2D, self.SplashTex)
        else:
            glBindTexture(GL_TEXTURE_2D, self.MainTex)

        # it's a good idea to enable state right before you need it
        # there's no such thing like global state intialization in
        # OpenGL
        glEnable(GL_TEXTURE_2D)
        # vertex arrays must be enabled using glEnableClientState
        glEnableClientState(GL_VERTEX_ARRAY)
        glEnableClientState(GL_TEXTURE_COORD_ARRAY)

        Varray = numpy.array([[0,0],[0,1],[1,1],[1,0]],numpy.float)
        glVertexPointer(2,GL_FLOAT,0,Varray)
        glTexCoordPointer(2,GL_FLOAT,0,Varray)
        indices = [0,1,2,3]
        glDrawElements(GL_QUADS,1,GL_UNSIGNED_SHORT,indices)

        # This implies a glFinish, which includes a glFlush
        glutSwapBuffers() 

# GLUT initialization in program global, so initialize it on
# the process level. It might be 
glutInit(sys.argv)

thing = ClassThing()
thing.run()

Answer 2

这可能是因为你调用了 glGenTextures(1) 两次吧？你在 TexFromPNG 里把它赋值给了 texture，然后又在 run 里把它赋值给了 self.MainTex。