pythonpython-3.xopenglglslglut
Trying to make alienrain in python using the opengl function glMapBufferRange
Just 4 little lines causing a problem with the alien rain program that I ported from the OpenGL Superbible. It seems I am having issues trying to write to memory after using the function glMapBufferRange
Update: Excellent code by Rabbid76 has solved the problem and provided valuable insight of explanation. Thank You.
Required files: ktxloader.py , aliens.ktx
Source code of alienrain.py
#!/usr/bin/python3
import sys
import time
sys.path.append("./shared")
#from sbmloader import SBMObject # location of sbm file format loader
from ktxloader import KTXObject # location of ktx file format loader
#from sbmath import m3dDegToRad, m3dRadToDeg, m3dTranslateMatrix44, m3dRotationMatrix44, m3dMultiply, m3dOrtho, m3dPerspective, rotation_matrix, translate, m3dScaleMatrix44
fullscreen = True
import numpy.matlib
import numpy as np
import math
try:
from OpenGL.GLUT import *
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.raw.GL.ARB.vertex_array_object import glGenVertexArrays, glBindVertexArray
except:
print ('''
ERROR: PyOpenGL not installed properly.
''')
sys.exit()
identityMatrix = [1,0,0,0, 0,1,0,0, 0,0,1,0, 0,0,0,1]
render_prog = GLuint(0)
render_vao = GLuint(0)
tex_alien_array = GLuint(0)
rain_buffer = GLuint(0)
droplet_x_offset = []
droplet_rot_speed = []
droplet_fall_speed = []
seed = 0x13371337
import random
import ctypes
random.seed (0x13371337)
def random_float():
# global seed
# res=0.0
# tmp=0
# seed *= 16807;
# tmp = seed ^ (seed >> 4) ^ (seed << 15);
# res = (tmp >> 9) | 0x3F800000;
# return (res - 1.0);
return (random.random() - 1.0)
class Scene:
def __init__(self, width, height):
global render_prog
global render_vao
global tex_alien_array
global rain_buffer
global droplet_x_offset, droplet_rot_speed, droplet_fall_speed
self.width = width
self.height = height
vs = GLuint(0)
fs = GLuint(0)
vs_source = '''
#version 410 core
layout (location = 0) in int alien_index;
out VS_OUT
{
flat int alien;
vec2 tc;
} vs_out;
struct droplet_t
{
float x_offset;
float y_offset;
float orientation;
float unused;
};
layout (std140) uniform droplets
{
droplet_t droplet[256];
};
void main(void)
{
const vec2[4] position = vec2[4](vec2(-0.5, -0.5),
vec2( 0.5, -0.5),
vec2(-0.5, 0.5),
vec2( 0.5, 0.5));
vs_out.tc = position[gl_VertexID].xy + vec2(0.5);
float co = cos(droplet[alien_index].orientation);
float so = sin(droplet[alien_index].orientation);
mat2 rot = mat2(vec2(co, so),
vec2(-so, co));
vec2 pos = 0.25 * rot * position[gl_VertexID];
gl_Position = vec4(pos.x + droplet[alien_index].x_offset,
pos.y + droplet[alien_index].y_offset,
0.5, 1.0);
vs_out.alien = alien_index % 64;
}
'''
fs_source = '''
#version 410 core
layout (location = 0) out vec4 color;
in VS_OUT
{
flat int alien;
vec2 tc;
} fs_in;
uniform sampler2DArray tex_aliens;
void main(void)
{
color = texture(tex_aliens, vec3(fs_in.tc, float(fs_in.alien)));
}
'''
vs = glCreateShader(GL_VERTEX_SHADER)
glShaderSource(vs, vs_source)
glCompileShader(vs)
glGetShaderInfoLog(vs)
fs = glCreateShader(GL_FRAGMENT_SHADER)
glShaderSource(fs, fs_source)
glCompileShader(fs)
glGetShaderInfoLog(vs)
render_prog = glCreateProgram()
glAttachShader(render_prog, vs)
glAttachShader(render_prog, fs)
glLinkProgram(render_prog)
glDeleteShader(vs)
glDeleteShader(fs)
glGetProgramInfoLog(render_prog)
glGenVertexArrays(1, render_vao)
glBindVertexArray(render_vao)
ktxobj = KTXObject()
tex_alien_array = ktxobj.ktx_load("aliens.ktx")
glBindTexture(GL_TEXTURE_2D_ARRAY, tex_alien_array)
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR)
glGenBuffers(1, rain_buffer)
glBindBuffer(GL_UNIFORM_BUFFER, rain_buffer)
glBufferData(GL_UNIFORM_BUFFER, 256*4*4, None, GL_DYNAMIC_DRAW)
for i in range(0, 256):
droplet_x_offset.append(random_float() * 2.0 - 1.0)
droplet_rot_speed.append( (random_float() + 0.5) * (-3.0 if (i & 1) else 3.0) )
droplet_fall_speed.append ( random_float() + 0.2 )
glBindVertexArray(render_vao);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
def display(self):
global rain_buffer
green = [ 0.0, 0.1, 0.0, 0.0 ]
currentTime = time.time()
t = currentTime
glViewport(0, 0, self.width, self.height)
glClearBufferfv(GL_COLOR, 0, green)
glUseProgram(render_prog);
glBindBufferBase(GL_UNIFORM_BUFFER, 0, rain_buffer);
droplet = glMapBufferRange(GL_UNIFORM_BUFFER, 0, 256*4*4, GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT)
float_array = ((ctypes.c_float * 4) * 256).from_address(droplet)
for i in range(0, 256):
float_array[i][0] = droplet_x_offset[i] + 2
float_array[i][1] = 2.0-math.fmod((t + float(i)) * droplet_fall_speed[i], 4.31 ) * random_float()
float_array[i][2] = droplet_rot_speed[i] * t * random_float() * math.pi
float_array[i][3] = 0.0
glUnmapBuffer(GL_UNIFORM_BUFFER);
for alien_index in range(0, 256):
glVertexAttribI1i(0, alien_index);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glutSwapBuffers()
def reshape(self, width, height):
self.width = width
self.height = height
def keyboard(self, key, x, y ):
global fullscreen
global many_cubes
print ('key:' , key)
if key == b'\x1b': # ESC
sys.exit()
elif key == b'f' or key == b'F': #fullscreen toggle
if (fullscreen == True):
glutReshapeWindow(512, 512)
glutPositionWindow(int((1360/2)-(512/2)), int((768/2)-(512/2)))
fullscreen = False
else:
glutFullScreen()
fullscreen = True
print('done')
def init(self):
pass
def timer(self, blah):
glutPostRedisplay()
glutTimerFunc( int(1/60), self.timer, 0)
time.sleep(1/60.0)
if __name__ == '__main__':
start = time.time()
glutInit()
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH)
glutInitWindowSize(512, 512)
w1 = glutCreateWindow('OpenGL SuperBible - Alien Rain')
glutInitWindowPosition(int((1360/2)-(512/2)), int((768/2)-(512/2)))
fullscreen = False
many_cubes = False
#glutFullScreen()
scene = Scene(512,512)
glutReshapeFunc(scene.reshape)
glutDisplayFunc(scene.display)
glutKeyboardFunc(scene.keyboard)
glutIdleFunc(scene.display)
#glutTimerFunc( int(1/60), scene.timer, 0)
scene.init()
glutMainLoop()
Current output is: Update: very similar to expected output. Except it very fast and the rotations of each alien are not as smooth as the expected output. If anyone wants to tinker with the values to get it, please do. Otherwise this question is answered.
The output should be:
Here's the alienrain.cpp that was used to create alienrain.py
Solution
First of all, the 2nd parameter of glBufferData is the buffer data in bytes.
Since the glsl data structure is
struct droplet_t
{
float x_offset;
float y_offset;
float orientation;
float unused;
};
layout (std140) uniform droplets
{
droplet_t droplet[256];
};
the buffer size is 4*4*256, because the size of a float is 4, t he structure has 4 elements of type flaot and the array has 256 elements
glBufferData(GL_UNIFORM_BUFFER, 256*4*4, None, GL_DYNAMIC_DRAW)
The instruction
droplet = glMapBufferRange(GL_UNIFORM_BUFFER, 0, 256*4*4, GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT)
returns a pointer to a allocated memory region with the proper size. You've to fill this memory with data.
The easiest solution is to use the (in python built-in) library ctypes, which has the handy function .from_address():
This method returns a ctypes type instance using the memory specified by address.
so the instruction
float_array = ((ctypes.c_float * 4) * 256).from_address(droplet)
"wraps" a 2 dimensional array to the memory addressed by droplet, with 256 elements and each element has 4 elements of type float.
The values can be set to the array, by a simple assignment statement. e.g.:
import random
import math
import ctypes
glBindBufferBase(GL_UNIFORM_BUFFER, 0, rain_buffer);
droplet = glMapBufferRange(GL_UNIFORM_BUFFER, 0, 256*4*4, GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT)
float_array = ((ctypes.c_float * 4) * 256).from_address(droplet)
for i in range(0, 256):
float_array[i][0] = random.random() * 2 -1
float_array[i][1] = random.random() * 2 -1
float_array[i][2] = random.random() * math.pi * 2
float_array[i][3] = 0.0