PyOpenGL将变量传递到顶点着色器

Question

经过几次建议，我决定用艰苦的方式学习一点OpenGL。我试图将(float-名为myAttrib(变量传递给顶点着色器，它似乎可以工作(第33行(，但显然不行。稍后，我将把代码分成更多的部分。

代码：

from OpenGL.GL import *
from OpenGL.GL.shaders import *
import pygame
from pygame.locals import *
import numpy, time
def getFileContent(file):
content = open(file, 'r').read()
return content
def initDraw():
pygame.init()
pygame.display.set_mode((640, 480), HWSURFACE | OPENGL | DOUBLEBUF)
vertices = [0.0, 0.5,
0.5, -0.5,
-0.5, -0.5,]
vertices = numpy.array(vertices, dtype = numpy.float32)
myAttrib = 0.3
vertexShader = compileShader(getFileContent("helloTriangle.vert"), GL_VERTEX_SHADER)
fragmentShader = compileShader(getFileContent("helloTriangle.frag"), GL_FRAGMENT_SHADER)
shaderProgram = glCreateProgram()
glAttachShader(shaderProgram, vertexShader)
glAttachShader(shaderProgram, fragmentShader)
glBindAttribLocation(shaderProgram, 1, "myAttrib")
glLinkProgram(shaderProgram)
print(glGetAttribLocation(shaderProgram, "myAttrib"))
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, vertices)
glEnableVertexAttribArray(0)
glClearColor(0, 0, 0, 1)
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
glUseProgram(shaderProgram)
glDrawArrays(GL_TRIANGLES, 0, 3)
pygame.display.flip()
time.sleep(2)
initDraw()

顶点着色器：

#version 130
attribute vec2 vPosition;
attribute float myAttrib;
void main()
{
gl_Position = vec4(vPosition.x, vPosition.y + myAttrib, 0.0, 1.0);
}

片段着色器：

#version 130
void main()
{
gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);            
}

Answer 1

如果使用属性，则必须定义一个通用顶点属性数组，每个顶点坐标有一个属性值(在您的情况下为3(。请参见顶点规范
如果您要使用uniform，那么您可以为存储在默认uniform块中的uniform变量中的程序设置一个值(您可以想象这在某种程度上类似于全局变量(。参见制服(GLSL(：

案例1-属性myAttrib:

顶点着色器

#version 130
attribute vec2 vPosition;
attribute float myAttrib;
void main()
{
gl_Position = vec4(vPosition.x, vPosition.y + myAttrib, 0.0, 1.0);
}

你必须定义一个通用顶点属性数组，就像你为顶点坐标所做的那样：

attrib = [-0.2, 0.2, 0.0]
myAttrib  = numpy.array(attrib, dtype = numpy.float32)
# .....
glLinkProgram(shaderProgram)
myAttrib_location = glGetAttribLocation(shaderProgram, "myAttrib")
# .....
glVertexAttribPointer(myAttrib_location, 1, GL_FLOAT, GL_FALSE, 0, myAttrib)
glEnableVertexAttribArray(myAttrib_location)

或

glBindAttribLocation(shaderProgram, 1, "myAttrib")
glLinkProgram(shaderProgram)
# .....
glVertexAttribPointer(1, 1, GL_FLOAT, GL_FALSE, 0, myAttrib)
glEnableVertexAttribArray(1)

情况2-均匀myUniform

顶点着色器

#version 130
attribute vec2 vPosition;
uniform float myUniform;
void main()
{
gl_Position = vec4(vPosition.x, vPosition.y + myUniform, 0.0, 1.0);
}

通过glGetUniformLocation获取制服的位置("myUniform"(，并通过glUniform:将值设置为制服

myUniform = 0.3
# .....
glLinkProgram(shaderProgram)
myUniform_location = glGetUniformLocation(shaderProgram, "myUniform")
# .....
glUseProgram(shaderProgram)
glUniform1f(myUniform_location, myUniform)
glDrawArrays(GL_TRIANGLES, 0, 3)