OpenGL PyQt对象无法缩放

问题描述

我刚刚使用VBO和VAO将旧的glBegin和glEnd代码转换为一个。作为框架，我正在使用Pyqt。我确实设法加载了3D对象并将其显示在屏幕上，但是我无法缩放它。我在paintGL方法中尝试了glLoadIdentity，但没有任何改变。我该如何缩放？ 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(0.0,1.0,0.3);
    }
    '''

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(0.2,0.2,0.7)
        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,-10.0)
        glScalef(0.2,0.2)
        glBindVertexArray(self.vertexArrayObject)
        glDrawArrays(GL_TRIANGLES,len(self.triangLevertices))
        glBindVertexArray(0)
        glFlush()

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

解决方法

如果仍然需要我们使用Legacy OpenGL固定函数矩阵堆栈，则必须通过顶点着色器中的gl_ModelViewProjectionMatrix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; 
}

---

请注意，只要立即模式（glBegin / glEnd序列）就不推荐使用矩阵堆栈。如今，顶点转换是通过用户定义的矩阵Uniform变量来完成的。另请参见GLSL Programming/Vector and Matrix Operations和Replacement for gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;