一、目的
1、画一个旋转的立方体，对正方体的六个面进行多纹理贴图；
二、程序运行结果
cube2.gif
三、片元着色器
顶点着色器是做出3D图像的轮廓框架（毛坯，进行空间与空间变化等与空间相关操作）
片元 着色器让它变得好看一些，即上色（装修，进行颜色与纹理等操作）
四、正方体多纹理贴图
把图片映射到正方体的6个面上，有两种方法：
1. 加载一个纹理图片，这个纹理图片包含6个面的信息，如图片2*3分割，每个块对应一个面。
2. 加载六个纹理图片，图片独立，每张图片对应一个面。
下面的例子采用第二种方法，使用多个纹理图片（不是多重纹理，多重纹理指纹理叠加，同一个面叠加多个纹理），绘制的时候，通过切换纹理图片的绑定来绘制不同的面，顶点坐标容易设计，正立方体的各个面都是规则的形状，纹理图片的4个顶点分别对应4个立方体表面顶点坐标即可。
注意：这种情况下，同一个顶点坐标，绘制不同的面时，对应的顶点坐标是不一样的，如绘制顶面和前侧面，有两个顶点坐标是一致的，但绘制这两个面对应的纹理坐标却不一致，大家可以看例子中的点{-0.5f, -0.5f, 0.5f }，绘制两个相邻的侧面，一个纹理坐标是{1.0f, 0.0f}, 一个是{0.0f, 0.0f},这种情况下使用glDrawElements的方式就要注意了，需处理好同一个顶点对应不同纹理坐标的情况。
本例子需要6张png图片，名称分别为wall0.png~wall5.png。
五、源代码
"""
程序名称：GL_DrawCube2.py
编程: dalong10
功能: 画一个立方体,给6个面加图像纹理,绕轴(0,0.7071,0.7071)旋转
"""
import myGL_Funcs #通用 OpenGL 程序,见 myGL_Funcs.py
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;
layout (location = 1) in vec2 inTexcoord;
out vec2 outTexcoord;
uniform float theta;
void main(){
mat4 rot=mat4( vec4(0.5+0.5*cos(theta), 0.5-0.5*cos(theta), -0.707106781*sin(theta), 0),
vec4(0.5-0.5*cos(theta),0.5+0.5*cos(theta), 0.707106781*sin(theta),0),
vec4(0.707106781*sin(theta), -0.707106781*sin(theta),cos(theta), 0.0),
vec4(0.0, 0.0,0.0, 1.0));
gl_Position=rot *vec4(position.x, position.y, position.z, 1.0);
outTexcoord = inTexcoord;
}
"""
strFS = """
#version 330 core
out vec4 FragColor;
in vec2 outTexcoord;
uniform sampler2D texture1;
void main(){
FragColor = texture(texture1, outTexcoord);
}
"""
class FirstCube:
def __init__(self, side):
self.side = side
# load shaders
self.program = myGL_Funcs.loadShaders(strVS, strFS)
glUseProgram(self.program)
# attributes
self.vertIndex = glGetAttribLocation(self.program, b"position")
self.texIndex = glGetAttribLocation(self.program, b"inTexcoord")
s = side/2.0
cube_vertices = [
-s, -s, -s,
s, -s, -s,
s, s, -s,
s, s, -s,
-s, s, -s,
-s, -s, -s,
-s, -s, s,
s, -s, s,
s, s, s,
s, s, s,
-s, s, s,
-s, -s, s,
-s, s, s,
-s, s, -s,
-s, -s, -s,
-s, -s, -s,
-s, -s, s,
-s, s, s,
s, s, s,
s, s, -s,
s, -s, -s,
s, -s, -s,
s, -s, s,
s, s, s,
-s, -s, -s,
s, -s, -s,
s, -s, s,
s, -s, s,
-s, -s, s,
-s, -s, -s,
-s, s, -s,
s, s,-s,
s, s, s,
s, s, s,
-s, s, s,
-s, s,-s
]
# texture coords
t=1.0
quadT = [
0,0, t,0, t,t, t,t, 0,t, 0,0,
0,0, t,0, t,t, t,t, 0,t, 0,0,
t,0, t,t, 0,t, 0,t, 0,0, t,0,
t,0, t,t, 0,t, 0,t, 0,0, t,0,
0,t, t,t, t,0, t,0, 0,0, 0,t,
0,t, t,t, t,0, t,0, 0,0, 0,t
]
# set up vertex array object (VAO)
self.vao = glGenVertexArrays(1)
glBindVertexArray(self.vao)
# set up VBOs
vertexData = numpy.array(cube_vertices, numpy.float32)
self.vertexBuffer = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, self.vertexBuffer)
glBufferData(GL_ARRAY_BUFFER, 4*len(vertexData), vertexData, GL_STATIC_DRAW)
tcData = numpy.array(quadT, numpy.float32)
self.tcBuffer = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, self.tcBuffer)
glBufferData(GL_ARRAY_BUFFER, 4*len(tcData), tcData,GL_STATIC_DRAW)
# enable arrays
glEnableVertexAttribArray(self.vertIndex)
glEnableVertexAttribArray(self.texIndex)
# Position attribute
glBindBuffer(GL_ARRAY_BUFFER, self.vertexBuffer)
glVertexAttribPointer(self.vertIndex, 3, GL_FLOAT, GL_FALSE, 0,None)
# TexCoord attribute
glBindBuffer(GL_ARRAY_BUFFER, self.tcBuffer)
glVertexAttribPointer(self.texIndex, 2, GL_FLOAT, GL_FALSE, 0,None)
# unbind VAO
glBindVertexArray(0)
glBindBuffer(GL_ARRAY_BUFFER, 0)
def render(self,texid,k):
self.texid = texid
# enable texture
glActiveTexture(GL_TEXTURE0)
glBindTexture(GL_TEXTURE_2D, self.texid)
# use shader
glUseProgram(self.program)
theta = i*PI/180.0
glUniform1f(glGetUniformLocation(self.program, "theta"), theta)
# bind VAO
glBindVertexArray(self.vao)
glEnable(GL_DEPTH_TEST)
# draw
glDrawArrays(GL_TRIANGLES, k*6, 6)
# 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(300, 300, "draw Cube ", 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)
PI = 3.14159265358979323846264
texid=[]
for k in range(6):
texture0= myGL_Funcs.loadTexture("wall"+str(k)+".png")
texid.append(texture0)
# Loop until the user closes the window
a=0
firstCube0 = FirstCube(1.0)
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.GL_DEPTH_BUFFER_BIT)
gl.glClearColor(0.0,0.0,4.0,0.0)
i=a
for k in range(6):
glBindTexture(GL_TEXTURE_2D, texid[k])
firstCube0.render(texid[k],k)
a=a+1
if a>360:
a=0
# Swap front and back buffers
glfw.swap_buffers(window)
# Poll for and process events
glfw.poll_events()
glfw.terminate()
六、参考资料
1、大龙10的简书：https://www.jianshu.com/p/49dec482a291
2、他山随悟的博客：https://blog.csdn.net/t3swing/article/details/78734159
