一、目的
1、给旋转的立方体加纹理。
二、程序运行结果
三、Z缓冲区
OpenGL存储它的所有深度信息于Z缓冲区(Z-buffer)中，也被称为深度缓冲区(Depth Buffer)。GLFW会自动为你生成这样一个缓冲区 (就如它有一个颜色缓冲区来存储输出图像的颜色)。深度存储在每个片段里面(作为片段的z值)当片段像输出它的颜色时，OpenGL会将它的深度值和z缓冲进行比较然后如果当前的片段在其它片段之后它将会被丢弃，然后重写。这个过程称为深度测试(Depth Testing)并且它是由OpenGL自动完成的。
opengl把每个像素点的z轴存放在深度缓冲中，当我们画一个像素点的时候，如果这个点的在之前相同位置点的z之后，那么则丢弃这个点，这个过程就是所谓的深度测试。
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
使用glEnable(GL_DEPTH_TEST)启用深度测试。
四、源代码
"""
glfw_cube02.py
Author: dalong10
Description: Draw a Cube, learning OPENGL
"""
import glutils #Common OpenGL utilities,see glutils.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 = glutils.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):
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, 0, 36)
# 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 = glutils.loadTexture("wall.png")
# 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
glBindTexture(GL_TEXTURE_2D, texid)
firstCube0.render(texid)
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()
五、参考文献
1、learnopengl教程https://learnopengl-cn.readthedocs.io/zh/latest/01%20Getting%20started/08%20Coordinate%20Systems/
2、大龙10https://www.jianshu.com/p/8e8730071ddf