我有以下代码,它应该只是在屏幕上绘制一个绿色三角形。它使用顶点数组对象和索引缓冲区进行绘制,并拥有我能制作的最简单的着色器。
起初我没有使用索引缓冲区,只是简单地进行了绘制调用,glDrawArrays
但当我将其更改为使用时glDrawElements
,屏幕上没有任何内容(它完全是黑色的)。
from OpenGL.GL import shaders
from OpenGL.arrays import vbo
from OpenGL.GL import *
from OpenGL.raw.GL.ARB.vertex_array_object import glGenVertexArrays, \
glBindVertexArray
import pygame
import numpy as np
def run():
pygame.init()
screen = pygame.display.set_mode((800,600), pygame.OPENGL)
#Create the Vertex Array Object
vertexArrayObject = GLuint(0)
glGenVertexArrays(1, vertexArrayObject)
glBindVertexArray(vertexArrayObject)
#Create the VBO
vertices = np.array([[0,1,0],[-1,-1,0],[1,-1,0]], dtype='f')
vertexPositions = vbo.VBO(vertices)
#Create the index buffer object
indices = np.array([0,1,2], dtype='uint16')
indexPositions = vbo.VBO(indices, target=GL_ELEMENT_ARRAY_BUFFER)
indexPositions.bind()
vertexPositions.bind()
glEnableVertexAttribArray(0) # from 'location = 0' in shader
glVertexAttribPointer(0, 3, GL_FLOAT, False, 0, None)
glBindVertexArray(0)
vertexPositions.unbind()
indexPositions.unbind()
#Now create the shaders
VERTEX_SHADER = shaders.compileShader("""
#version 330
layout(location = 0) in vec4 position;
void main()
{
gl_Position = position;
}
""", GL_VERTEX_SHADER)
FRAGMENT_SHADER = shaders.compileShader("""
#version 330
out vec4 outputColor;
void main()
{
outputColor = vec4(0.0f, 1.0f, 0.0f, 1.0f);
}
""", GL_FRAGMENT_SHADER)
shader = shaders.compileProgram(VERTEX_SHADER, FRAGMENT_SHADER)
#The draw loop
while True:
glUseProgram(shader)
glBindVertexArray(vertexArrayObject)
#glDrawArrays(GL_TRIANGLES, 0, 3) #This line works
glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_INT, 0) #This line does not
glBindVertexArray(0)
glUseProgram(0)
# Show the screen
pygame.display.flip()
run()
如果我只是注释掉glDrawElements
并取消注释该glDrawArrays
行,那么它可以正常工作,因此至少顶点 VBO 被正确输入。
我在这里做错了什么?我能够找到的所有 OpenGL 文档都表明我这样做是正确的,所以我显然误解了关于 OpenGL 本身或 PyOpenGL 包装器的一些东西。
编辑
更改 VAO 设置以使用更直接的 OpenGL 函数而不是 VBO 包装器,例如:
vertices = np.array([[0,1,0],[-1,-1,0],[1,-1,0]], dtype='f')
vertexPositions = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, vertexPositions)
glBufferData(GL_ARRAY_BUFFER, vertices, GL_STATIC_DRAW)
#Create the index buffer object
indices = np.array([0,1,2], dtype='uint16')
indexPositions = glGenBuffers(1)
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexPositions)
glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices, GL_STATIC_DRAW)
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexPositions)
glBindBuffer(GL_ARRAY_BUFFER, vertexPositions)
glEnableVertexAttribArray(0) # from 'location = 0' in shader
glVertexAttribPointer(0, 3, GL_FLOAT, False, 0, None)
glBindVertexArray(0)
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0)
glBindBuffer(GL_ARRAY_BUFFER, 0)
没什么区别。glDrawArrays
仍然有效,glDrawElements
但仍然无效。