PyOpenGL 将变量传递给顶点着色器

Question

经过一些建议后，我决定通过困难的方式学习一点 OpenGL。我试图将一个 (float - 命名为 myAttrib) 变量传递给顶点着色器，它似乎可以工作（第 33 行），但显然没有。稍后我想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

如果您使用属性，则必须定义一组通用顶点属性，每个顶点坐标有一个属性值（在您的例子中为 3 个）。参见 Vertex Specification。
如果您要使用制服，则可以为存储在默认制服块中的制服变量中的程序设置一个值（您可以将其想象成全局变量）。见 Uniform (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);
}

您必须像为顶点坐标那样定义一个通用顶点属性数组：

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)

案例 2 - 制服 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 and set the value to the uniform by glUniform:

获取制服("myUniform")的位置

myUniform = 0.3

# .....

glLinkProgram(shaderProgram)
myUniform_location = glGetUniformLocation(shaderProgram, "myUniform")

# .....

glUseProgram(shaderProgram)
glUniform1f(myUniform_location, myUniform)

glDrawArrays(GL_TRIANGLES, 0, 3)

PyOpenGL 将变量传递给顶点着色器

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