glMultiDrawArraysIndirect函数怎么会出错

Question

我正在使用Python和Modern OpenGL进行编程，我试图在代码中实现glMultiDrawArraysIndirect函数来绘制一个简单的形状，我想稍后将其应用于更复杂的事情，但这只是一个简单测试，我不知道错误的确切位置。

import glfw, time, ctypes, math, pyrr
import numpy as np
from OpenGL.GL import *
from OpenGL.GL.shaders import *
glfw.init()
glfw.window_hint(glfw.SAMPLES, 4)
w = glfw.create_window(640, 480, "Galeria das Sombras", None, None)
glfw.make_context_current(w)
v = """
#version 430
in layout(location=0) vec3 posicao;
in layout(location=1) vec2 textura;
uniform mat4 view;
uniform vec3 def;
uniform vec3 pos;
uniform vec3 scale;
uniform float giro;
uniform float giro2;
out vec2 texcords;
void main(){
texcords = textura;
vec3 p = vec3(posicao.x*scale.x,posicao.y*scale.y,posicao.z*scale.z);
p = p+def;
p = vec3(-sin(giro)*p.z+cos(giro)*p.x,p.y,sin(giro)*p.x+cos(giro)*p.z);
p = vec3(p.x,-sin(giro2)*p.z+cos(giro2)*p.y,sin(giro2)*p.y+cos(giro2)*p.z);
p = p+pos+vec3(gl_InstanceID,0,0);
gl_Position = view*vec4(p,1);
}
"""
f = """
#version 430
in vec2 texcords;
uniform vec3 cor;
uniform sampler2D texinfo;
void main(){
gl_FragColor = vec4(cor,1)*texture(texinfo,texcords);
}
"""
shader = compileProgram(compileShader(v,GL_VERTEX_SHADER),compileShader(f,GL_FRAGMENT_SHADER))
tudo = [-1,-1,0,0,1,
1,-1,0,1,1,
1,1,0,1,0,
-1,1,0,0,0]
tudo = np.array(tudo, np.float32)
VBO = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glBufferData(GL_ARRAY_BUFFER, len(tudo)*4, tudo, GL_STATIC_DRAW)
'''
tudo = [[1,1,0,3],[2,2,1,3]]
tudo = np.array(tudo, np.uint8)
VBI = glGenBuffers(1)
glBindBuffer(GL_DRAW_INDIRECT_BUFFER, VBI)
glBufferData(GL_DRAW_INDIRECT_BUFFER, len(tudo)*4, tudo, GL_STATIC_DRAW)
'''
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 20, ctypes.c_void_p(0))
glEnableVertexAttribArray(0)
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 20, ctypes.c_void_p(12))
glEnableVertexAttribArray(1)
glUseProgram(shader)
view = pyrr.matrix44.create_perspective_projection_matrix(60, 640/480, .1, 1000)
p = glGetUniformLocation(shader, "view")
glUniformMatrix4fv(p, 1, GL_FALSE, view)
glEnable(GL_DEPTH_TEST)
glEnable(GL_MULTISAMPLE)
glEnable(GL_TEXTURE_2D)
from PIL import Image
t = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, t)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
buffer = Image.open("p.jpg")
data = buffer.tobytes()
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, buffer.size[0], buffer.size[1], 0, GL_RGB, GL_UNSIGNED_BYTE, data)
girar = 0
tempo = glfw.get_time()
tfps = glfw.get_time()
fps = 0
action = 0
while not glfw.window_should_close(w):
glfw.swap_buffers(w)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
view = pyrr.matrix44.create_perspective_projection_matrix(60, glfw.get_window_size(w)[0]/glfw.get_window_size(w)[1], .1, 1000)
p = glGetUniformLocation(shader, "view")
glUniformMatrix4fv(p, 1, GL_FALSE, view)
glViewport(0,0,glfw.get_window_size(w)[0],glfw.get_window_size(w)[1])
p = glGetUniformLocation(shader, "cor")
glUniform3f(p, 1, 0, 0)
p = glGetUniformLocation(shader, "def")
glUniform3f(p, 0, 0, 0)
p = glGetUniformLocation(shader, "scale")
glUniform3f(p, 1, 1, 1)
p = glGetUniformLocation(shader, "giro")
glUniform1f(p, girar*math.pi/180)
if glfw.get_time() - tempo > 1/60:
girar+=1
tempo = glfw.get_time()
if action > 0:
action-=.05
if action < 0:
action = 0
p = glGetUniformLocation(shader, "giro2")
if glfw.get_key(w, glfw.KEY_W) and action == 0:
action = 2
if action > 1:
glUniform1f(p, (1-(action-1))*-90*(math.pi/180))
else:
glUniform1f(p, action*-90*(math.pi/180))
p = glGetUniformLocation(shader, "pos")
glUniform3f(p, 0, 0, -10)
glMultiDrawArraysIndirect(GL_TRIANGLES, np.array([[0,3,1,0],[1,3,1,1]]), 2, 1)
fps+=1
if glfw.get_time() - tfps > 1:
print("FPS:",fps)
fps = 0
tfps = glfw.get_time()
glfw.poll_events()
if fps > 400:
time.sleep(.01)
glfw.destroy_window(w)
glfw.terminate()

在VBO中有一个正方形，但我只打算用前三个点画两个三角形，然后用最后三个点挨着画，我在互联网上找不到很多这种代码的例子，只有glMultiDrawArraysIndirect文档，但我无法在代码中运行它，至少在没有很好锁定的情况下，当我将drawcount更改为1个轮子，但屏幕上什么都没有出现时。

有和我从网站上获取的drawcount：http://docs.gl/gl4/glMultiDrawArraysIndirect

我试图更改不同类型numpy数组的indirect值，使用不同的uintdtypes，但大多数数组要么出错，要么运行时屏幕上没有任何显示，有人知道出了什么问题吗？

Answer 1

指定NumPy数组时，需要指定类型uint32。最后一个参数(步幅(指定绘制参数数组元素之间的距离(以基本机器为单位((16字节(：
(请参阅glMultiDrawArraysIndirect(

indirect = np.array([[3, 10, 0, 0], [3, 5, 1, 0]], dtype=np.uint32)
glMultiDrawArraysIndirect(GL_TRIANGLES, indirect, 2, 16)

或

glMultiDrawArraysIndirect(GL_TRIANGLES, indirect, 
indirect.shape[0], indirect.dtype.itemsize * indirect.shape[1])

上述代码的作用与：
(请参阅glDrawArraysIndirect(相同

indirect1 = np.array([3, 10, 0, 0], dtype=np.uint32)
glDrawArraysIndirect(GL_TRIANGLES, indirect1)
indirect2 = np.array([3, 5, 1, 0], dtype=np.uint32)
glDrawArraysIndirect(GL_TRIANGLES, indirect2)

分别与：
(见glDrawArraysInstancedBaseInstance(相同

glDrawArraysInstancedBaseInstance(GL_TRIANGLES, 0, 3, 10, 0)
glDrawArraysInstancedBaseInstance(GL_TRIANGLES, 1, 3, 5, 0)

---

使用glDrawArraysIndirect或glMultiDrawArraysIndirect时，需要创建以下数据结构：(参见GLAPI/glMultiDrawArraysIndirect(

typedef  struct {
uint  count;
uint  instanceCount;
uint  first;
uint  baseInstance;
} DrawArraysIndirectCommand;

这可以使用数据类型为uint32:的NumPy数组来实现

np.array([count, instanceCount, first, baseInstance], dtype=np.uint32)