OpenGL PyQt 对象不缩放

Posted 2023-02-16

【中文标题】OpenGL PyQt 对象不缩放

【英文标题】：OpenGL PyQt object not scaling

【发布时间】：2020-08-31 11:15:02

【问题描述】：

我刚刚使用 VBO 和 VAO 将旧的 glBegin 和 glEnd 代码翻译成一个。作为框架，我使用的是 Pyqt。我确实设法加载了一个 3D 对象并将其显示在屏幕上，但我无法缩放它。我在paintGL方法中尝试了glLoadIdentity，但没有任何改变。我怎么能缩放它？ 这是我的代码：

vertex_code = '''
    attribute vec2 position;
    void main()
    
        gl_Position = vec4(position, 0.0, 1.0);
        gl_Position.y -= 0.5;
    
    '''
fragment_code = '''
    void main()
    
        gl_FragColor = vec4(0.0, 1.0, 1.0, 0.3);
    
    '''

class ObjRender(QOpenGLWidget):
  
    def __init__(self, parent):
        QGLWidget.__init__(self, parent)
        self.object = ObjectLoader("myobj.obj")
        self.triangleVertices = []
        self.angle = 0
   
  
    def initializeGL(self):
        glEnable(GL_DEPTH_TEST)
        glShadeModel(GL_FLAT)
        glDisable(GL_CULL_FACE)

        program = glCreateProgram()
        vertex = glCreateShader(GL_VERTEX_SHADER)
        fragment = glCreateShader(GL_FRAGMENT_SHADER)

        glShaderSource(vertex, vertex_code)
        glShaderSource(fragment, fragment_code)
        
        glCompileShader(vertex)
        ## handle errors
        glCompileShader(fragment)
        ## handle errors 

        glAttachShader(program, vertex)
        glAttachShader(program, fragment)

        glLinkProgram(program)
        ## handle errors

        glDetachShader(program, vertex)
        glDetachShader(program, fragment)
        
        glUseProgram(program)

        ## build data
        glClearColor(0.2, 0.2, 0.2, 0.7)
        glClearDepth(1.0)
        glEnable(GL_DEPTH_TEST)

        self.initializeVertices()
        self.triangleVertices = array(self.triangleVertices, 'f')

        self.vertexBufferObject = VBO(self.triangleVertices)
        self.vertexBufferObject.bind()

        self.vertexArrayObject = glGenVertexArrays(1)

        glBindVertexArray(self.vertexArrayObject)
        glEnableClientState(GL_VERTEX_ARRAY)
        glVertexPointer(3, GL_FLOAT, 3*self.triangleVertices.itemsize, None)
        glBindVertexArray(0)

        glMatrixMode(GL_PROJECTION)
        glLoadIdentity()
    def paintGL(self):
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
        glLoadIdentity()
        glTranslatef(0.0, 0.0, -10.0)
        glScalef(0.2, 0.2, 0.2)
        glBindVertexArray(self.vertexArrayObject)
        glDrawArrays(GL_TRIANGLES, 0, len(self.triangleVertices))
        glBindVertexArray(0)
        glFlush()

    
    def resizeGL(self, width, height):    
        glViewport(0, 0, width, height)
        gluPerspective(45, 2.0, 7.0, 1000.0)

【参考方案1】：

如果你还想要我们Legacy OpenGL固定函数矩阵栈，那么你必须在顶点着色器中通过gl_ModelViewProjectionMatrix来变换顶点位置：

attribute vec2 position;

void main()

    vec4 pos = vec4(position.x, position.y-0.5, 0.0, 1.0);
    gl_Position = gl_ModelViewProjectionMatrix * pos; 

---

注意，只要立即模式（glBegin/glEnd 序列），矩阵堆栈就会被弃用。如今，顶点变换由用户定义的矩阵Uniform 变量完成。另见GLSL Programming/Vector and Matrix Operations 和Replacement for gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;