一、目的

1、畫平面直角坐標系；

二、程序運行結果

平面直角坐標系

三、numpy.hstack()函數

1、函數

函數原型：numpy.hstack(tup)，其中tup是arrays序列，陣列必須具有相同的形狀，除了對應于軸的維度(默認情況下，第一個)。

等價于np.concatenate(tup,axis=1)

2、例1

>>> import numpy as np

>>> a=np.array((1,2,3))

>>> b=np.array((4,5,6))

>>> np.hstack((a,b))

array([1, 2, 3, 4, 5, 6])

3、例2

>>> a=np.array(([1],[2],[3]))

>>> b=np.array(([4],[5],[6]))

>>> np.hstack((a,b))

array([[1, 4],

[2, 5],

[3, 6]])

四、glDrawArrays 函數

1、函數原型：

GL_APICALL void GL_APIENTRY glDrawArrays (GLenum mode, GLint first, GLsizei count);

提供繪制功能。當采用頂點數組方式繪制圖形時，使用該函數。該函數根據頂點數組中的坐標數據和指定的模式，進行繪制。

相似功能的函數是 glDrawElements。

2、參數說明：

mode，繪制方式，OpenGL2.0以后提供以下參數：GL_POINTS、GL_LINES、GL_LINE_LOOP、GL_LINE_STRIP、GL_TRIANGLES、GL_TRIANGLE_STRIP、GL_TRIANGLE_FAN。

first，從數組緩存中的哪一位開始繪制，一般為0。

count，數組中頂點的數量。

五、源代碼

"""

dalong2020_1.py

Author: dalong10

Description: Draw a Rectangular Coordinates, learning OPENGL

"""

import glutils #Common OpenGL utilities,see glutils.py,見 之二

import sys, random, math

import OpenGL

from OpenGL.GL import *

from OpenGL.GL.shaders import *

import numpy

import numpy as np

import glfw

strVS = """

#version 330 core

layout(location = 0) in vec3 position;

void main(){

gl_Position = vec4(position.x, position.y, position.z, 1.0);

}

"""

strFS = """

#version 330 core

out vec4 color;

void main(){

color = vec4(0.0, 1.0, 0.0, 1.0);

}

"""

class FirstCircle:

def __init__(self, myvertices):

self.vertices = myvertices

# load shaders

self.program = glutils.loadShaders(strVS, strFS)

glUseProgram(self.program)

vertices = myvertices

# set up vertex array object (VAO)

self.vao = glGenVertexArrays(1)

glBindVertexArray(self.vao)

# set up VBOs

vertexData = numpy.array(vertices, numpy.float32)

self.vertexBuffer = glGenBuffers(1)

glBindBuffer(GL_ARRAY_BUFFER, self.vertexBuffer)

glBufferData(GL_ARRAY_BUFFER, 4*len(vertexData), vertexData,

GL_STATIC_DRAW)

#enable arrays

self.vertIndex = 0

glEnableVertexAttribArray(self.vertIndex)

# set buffers

glBindBuffer(GL_ARRAY_BUFFER, self.vertexBuffer)

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, None)

# unbind VAO

glBindVertexArray(0)

def render(self, myFS):

# use shader

glUseProgram(self.program)

# bind VAO

glBindVertexArray(self.vao)

# draw

glDrawArrays(GL_LINES, 0, self.vertices.size )

# unbind VAO

glBindVertexArray(0)

if __name__ == '__main__':

import sys

import glfw

import OpenGL.GL as gl

def on_key(window, key, scancode, action, mods):

if key == glfw.KEY_ESCAPE and action == glfw.PRESS:

glfw.set_window_should_close(window,1)

# Initialize the library

if not glfw.init():

sys.exit()

# Create a windowed mode window and its OpenGL context

window = glfw.create_window(400, 400, "Rectangular Coordinates", None, None)

if not window:

glfw.terminate()

sys.exit()

# Make the window's context current

glfw.make_context_current(window)

# Install a key handler

glfw.set_key_callback(window, on_key)

t=0.9

c=numpy.array([-t,0,0, t,0,0 , 0,t,0 , 0, -t, 0] , numpy.float32) #X,Y軸

for i in range(19): #X軸畫線

x=float(t*(-9.0+i)/10)

c_i=numpy.array([x,0,0,x,0.02,0], numpy.float32)

c=np.hstack((c,c_i ))

c_i=numpy.array([t,0,0,t-0.02,0.02,0 , t,0,0,t-0.02,-0.02,0 ], numpy.float32)

c=np.hstack((c,c_i ))

for i in range(19): #Y軸畫線

y=float(t*(-9.0+i)/10)

c_i=numpy.array([0,y,0,0.02,y,0], numpy.float32)

c=np.hstack((c,c_i ))

c_i=numpy.array([0,t,0,0.02,t-0.02,0 ,0, t,0,-0.02,t-0.02,0 ], numpy.float32)

c=np.hstack((c,c_i ))

# Loop until the user closes the window

while not glfw.window_should_close(window):

# Render here

width, height = glfw.get_framebuffer_size(window)

ratio = width / float(height)

gl.glViewport(0, 0, width, height)

gl.glClear(gl.GL_COLOR_BUFFER_BIT)

gl.glClearColor(0.0,0.0,4.0,0.0)

firstCircle0 = FirstCircle(c)

# render

firstCircle0.render(0)

# Swap front and back buffers

glfw.swap_buffers(window)

# Poll for and process events

glfw.poll_events()

glfw.terminate()

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