Python，OpenGL：如何在 GPU 上存储顶点数据

Question

我需要在 2D 中显示大量四边形，使用 Python 和 OpenGL 制作它的最佳方法是什么？目标是不在调用paintGL时将所有数据发送到GPU，因为这需要很多时间......我想必须有可能在GPU上存储顶点数据，如何在 Python 中实现它？这是我的问题的工作示例：

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from OpenGL.GL import *
from PyQt4 import QtGui, QtCore, QtOpenGL

def get_squares(squareCount, edgeSize):

    """
    Returns vertex list for a matrix of squares

    squareCount - number of squares on one edge
    edgeSize - size of the matrix edge
    """

    edgeLength = edgeSize/squareCount/2
    vertexList = []
    x = edgeLength/2
    y = edgeLength/2
    z = 0
    for i in range(squareCount):
        for j in range(squareCount):
            vertexList.append([x,y,z])
            y += edgeLength
            vertexList.append([x,y,z])
            x += edgeLength
            vertexList.append([x,y,z])
            y -= edgeLength
            vertexList.append([x,y,z])
            x += edgeLength
        x = edgeLength/2
        y += 2*edgeLength
    return vertexList


class OpenGLWidget(QtOpenGL.QGLWidget):
    def __init__(self, squareCount = 20, parent = None):
        QtOpenGL.QGLWidget.__init__(self, parent)
        self.squares = get_squares(squareCount, 50)

    def paintGL(self):
        glBegin(GL_QUADS)
        for point in self.squares:
            glVertex3f(*point)
        glEnd()

    def resizeGL(self, w, h):
        glMatrixMode(GL_PROJECTION)
        glLoadIdentity()
        glOrtho(0, 50, 0, 50, 0, 1)
        glViewport(0, 0, w, h)

    def initializeGL(self):
        glClearColor(0.0, 0.0, 0.0, 1.0)
        glClear(GL_COLOR_BUFFER_BIT)

if __name__ == '__main__':
    import sys
    app = QtGui.QApplication([])
    w = OpenGLWidget(squareCount = 20) # try increasing that number and resizing the window...
                                       # for me at squareCount = 200 (40000 squares) it's really slow
    w.show()
    sys.exit(app.exec_())

Answer 1

我使用 Python-OpenGL 和 numpy 来执行此操作。示例代码：

import numpy

Verts = numpy.array([
    ( -0.5,  0.5, -0.5 ),   # left top rear
    (  0.5,  0.5, -0.5 ),   # right top rear
    (  0.5, -0.5, -0.5 ),   # right bottom rear
    ( -0.5, -0.5, -0.5 ),   # left bottom rear
    ( -0.5,  0.5,  0.5 ),   # left top front
    (  0.5,  0.5,  0.5 ),   # right top front
    (  0.5, -0.5,  0.5 ),   # right bottom front
    ( -0.5, -0.5,  0.5 ),   # left bottom front
], dtype=numpy.float32)

Faces = numpy.array([
    7, 6, 5, 4,     # front
    6, 2, 1, 5,     # right
    3, 7, 4, 0,     # left
    5, 1, 0, 4,     # top
    3, 2, 6, 7,     # bottom
    2, 3, 0, 1,     # rear
], dtype=numpy.int16)

class Cube (object):
    "Wireframe cube implemented with VBOs"

    def __init__ (self, color = (0.0, 1.0, 0.0, 1.0)):
        self.vert = glGenBuffers(1)
        self.rgba = glGenBuffers(1)
        self.idx  = glGenBuffers(1)

        glBindBuffer(GL_ARRAY_BUFFER, self.vert)
        glBufferData(GL_ARRAY_BUFFER, Verts, GL_STATIC_DRAW)
        colorTable = numpy.array([color for n in range(0, len(Verts))], dtype=numpy.float32)
        glBindBuffer(GL_ARRAY_BUFFER, self.rgba)
        glBufferData(GL_ARRAY_BUFFER, colorTable, GL_STATIC_DRAW)
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, self.idx)
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, Faces, GL_STATIC_DRAW)

    def draw (self):
        glBindBuffer(GL_ARRAY_BUFFER, self.vert)
        glVertexPointer(3, GL_FLOAT, 0, None)
        glBindBuffer(GL_ARRAY_BUFFER, self.rgba)
        glColorPointer(4, GL_FLOAT, 0, None)
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, self.idx)
        glDrawElements(GL_QUADS, len(Faces), GL_UNSIGNED_SHORT, None)