pyopengl, texturecoordinates for vertex lists [duplicate] - opengl

Question

I am working on a project and I need to use texture arrays to apply textures. I have asked many questions about this, none of which I got an answer I was completely satisfied with (Get access to later versions of GLSL , OpenGL: Access Array Texture in GLSL , and OpenGL: How would I implement texture arrays?) so I'm asking a more broad question to hopefully get a response. Anyways, How would I texture an object in OpenGL (PyOpenGL more specifically, but it's fine if you put your answer in C++). I already have a way to load the texture arrays, just not a way to apply it. This is the desired result:
Image from opengl-tutorial
and this is what I currently have for loading array textures:
def load_texture_array(path,width,height):
teximg = pygame.image.load(path)
texels = teximg.get_buffer().raw
texture = GLuint(0)
layerCount = 6
mipLevelCount = 1
glGenTextures(1, texture)
glBindTexture(GL_TEXTURE_2D_ARRAY, texture)
glTexStorage3D(GL_TEXTURE_2D_ARRAY, mipLevelCount, GL_RGBA8, width, height, layerCount)
glTexSubImage3D(GL_TEXTURE_2D_ARRAY, 0, 0, 0, 0, width, height, layerCount, GL_RGBA, GL_UNSIGNED_BYTE, texels)
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE)
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE)
TLDR: How would I apply textures to objects in OpenGL using texture arrays?
I will happily provide any other information if necessary.

Answer 1

If you want to use a 2D Array Texture for a cube, each of the 6 textures for the 6 side must be the same size.
You can lookup the texture by 3 dimensional texture coordinates. The 3rd component of the texture coordinate is the index of the 2d texture in the 2d texture array.
Hence the texture coordinates for the 6 sides are
0: [(0, 0, 0), (1, 0, 0), (1, 1, 0), (0, 1, 0)]
1: [(0, 0, 1), (1, 0, 1), (1, 1, 1), (0, 1, 1)]
2: [(0, 0, 2), (1, 0, 2), (1, 1, 2), (0, 1, 2)]
3: [(0, 0, 3), (1, 0, 3), (1, 1, 3), (0, 1, 3)]
4: [(0, 0, 4), (1, 0, 4), (1, 1, 4), (0, 1, 4)]
5: [(0, 0, 5), (1, 0, 5), (1, 1, 5), (0, 1, 5)]
Get the 3 dimensional texture coordinate attribute in the vertex shader and pass it to the fragment shader:
in a_uv;
out v_uv;
// [...]
void main()
{
v_uv = a_uv;
// [...]
}
Use the 3 dimensional texture coordinate to look up the sampler2DArray in the fragment shader:
out v_uv;
uniform sampler2DArray u_texture;
// [...]
void main()
{
vec4 texture(u_texture, v_uv.xyz);
// [...]
}
Create a GL_TEXTURE_2D_ARRAY and use glTexSubImage3D to load 6 2-dimensional images to the 6 planes of the 2D Array Texture. In the following image_planes is a list with the 6 2-dimensional image planes:
tex_obj = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D_ARRAY, self.tex_obj)
glTexImage3D(GL_TEXTURE_2D_ARRAY, 0, GL_RGBA, sizeX, sizeY, 6, 0, GL_RGBA, GL_UNSIGNED_BYTE, None)
for i in range(6):
glTexSubImage3D(GL_TEXTURE_2D_ARRAY, 0, 0, 0, i, sizeX, sizeY, 1, GL_RGBA, GL_UNSIGNED_BYTE, image_planes[i])
glTexParameterf(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
glTexParameterf(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
See also PyGame and OpenGL 4.
Minimal example:
import os, math, ctypes
import glm
from OpenGL.GL import *
from OpenGL.GL.shaders import *
from OpenGL.arrays import *
import pygame
pygame.init()
image_path = r"images"
image_names = ["banana64.png", "apple64.png", "fish64.png", "rocket64.png", "ice64.png", "boomerang64.png"]
image_planes = [
(GLubyte * 4)(255, 0, 0, 255), (GLubyte * 4)(0, 255, 0, 255), (GLubyte * 4)(0, 0, 255, 255),
(GLubyte * 4)(255, 255, 0, 255), (GLubyte * 4)(0, 255, 255, 255), (GLubyte * 4)(255, 0, 255, 255)]
image_size = (1, 1)
for i, filename in enumerate(image_names):
try:
image = pygame.image.load(os.path.join(image_path, filename))
image_size = image.get_size()
image_planes[i] = pygame.image.tostring(image, 'RGBA')
except:
pass
class MyWindow:
__glsl_vert = """
#version 130
in vec3 a_pos;
in vec3 a_nv;
in vec3 a_uv;
out vec3 v_pos;
out vec3 v_nv;
out vec3 v_uv;
uniform mat4 u_proj;
uniform mat4 u_view;
uniform mat4 u_model;
void main()
{
mat4 model_view = u_view * u_model;
mat3 normal = mat3(model_view);
vec4 view_pos = model_view * vec4(a_pos.xyz, 1.0);
v_pos = view_pos.xyz;
v_nv = normal * a_nv;
v_uv = a_uv;
gl_Position = u_proj * view_pos;
}
"""
__glsl_frag = """
#version 130
out vec4 frag_color;
in vec3 v_pos;
in vec3 v_nv;
in vec3 v_uv;
uniform sampler2DArray u_texture;
void main()
{
vec3 N = normalize(v_nv);
vec3 V = -normalize(v_pos);
float ka = 0.1;
float kd = max(0.0, dot(N, V)) * 0.9;
vec4 color = texture(u_texture, v_uv.xyz);
frag_color = vec4(color.rgb * (ka + kd), color.a);
}
"""
def __init__(self, w, h):
self.__caption = 'OpenGL Window'
self.__vp_size = [w, h]
pygame.display.gl_set_attribute(pygame.GL_DEPTH_SIZE, 24)
self.__screen = pygame.display.set_mode(self.__vp_size, pygame.DOUBLEBUF| pygame.OPENGL)
self.__program = compileProgram(
compileShader( self.__glsl_vert, GL_VERTEX_SHADER ),
compileShader( self.__glsl_frag, GL_FRAGMENT_SHADER ),
)
self.___attrib = { a : glGetAttribLocation (self.__program, a) for a in ['a_pos', 'a_nv', 'a_uv'] }
print(self.___attrib)
self.___uniform = { u : glGetUniformLocation (self.__program, u) for u in ['u_model', 'u_view', 'u_proj'] }
print(self.___uniform)
v = [[-1,-1,1], [1,-1,1], [1,1,1], [-1,1,1], [-1,-1,-1], [1,-1,-1], [1,1,-1], [-1,1,-1]]
n = [[0,0,1], [1,0,0], [0,0,-1], [-1,0,0], [0,1,0], [0,-1,0]]
e = [[0,1,2,3], [1,5,6,2], [5,4,7,6], [4,0,3,7], [3,2,6,7], [1,0,4,5]]
t = [[0, 0], [1, 0], [1, 1], [0, 1]]
index_array = [si*4+[0, 1, 2, 0, 2, 3][vi] for si in range(6) for vi in range(6)]
attr_array = []
for si in range(len(e)):
for i, vi in enumerate(e[si]):
attr_array += [*v[vi], *n[si], *t[i], si]
self.__no_vert = len(attr_array) // 10
self.__no_indices = len(index_array)
vertex_attributes = (ctypes.c_float * len(attr_array))(*attr_array)
indices = (ctypes.c_uint32 * self.__no_indices)(*index_array)
self.__vao = glGenVertexArrays(1)
self.__vbo, self.__ibo = glGenBuffers(2)
glBindVertexArray(self.__vao)
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, self.__ibo)
glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices, GL_STATIC_DRAW)
glBindBuffer(GL_ARRAY_BUFFER, self.__vbo)
glBufferData(GL_ARRAY_BUFFER, vertex_attributes, GL_STATIC_DRAW)
float_size = ctypes.sizeof(ctypes.c_float)
glVertexAttribPointer(self.___attrib['a_pos'], 3, GL_FLOAT, False, 9*float_size, None)
glVertexAttribPointer(self.___attrib['a_nv'], 3, GL_FLOAT, False, 9*float_size, ctypes.c_void_p(3*float_size))
glVertexAttribPointer(self.___attrib['a_uv'], 3, GL_FLOAT, False, 9*float_size, ctypes.c_void_p(6*float_size))
glEnableVertexAttribArray(self.___attrib['a_pos'])
glEnableVertexAttribArray(self.___attrib['a_nv'])
glEnableVertexAttribArray(self.___attrib['a_uv'])
glEnable(GL_DEPTH_TEST)
glUseProgram(self.__program)
glActiveTexture(GL_TEXTURE0)
sizeX, sizeY = image_size
self.tex_obj = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D_ARRAY, self.tex_obj)
glTexImage3D(GL_TEXTURE_2D_ARRAY, 0, GL_RGBA, sizeX, sizeY, 6, 0, GL_RGBA, GL_UNSIGNED_BYTE, None)
for i in range(6):
glTexSubImage3D(GL_TEXTURE_2D_ARRAY, 0, 0, 0, i, sizeX, sizeY, 1, GL_RGBA, GL_UNSIGNED_BYTE, image_planes[i])
glTexParameterf(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
glTexParameterf(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
def run(self):
self.__starttime = 0
self.__starttime = self.elapsed_ms()
run = True
while run:
for event in pygame.event.get():
if event.type == pygame.QUIT:
run = False
self.__mainloop()
pygame.display.flip()
pygame.quit()
def elapsed_ms(self):
return pygame.time.get_ticks() - self.__starttime
def __mainloop(self):
proj, view, model = glm.mat4(1), glm.mat4(1), glm.mat4(1)
aspect = self.__vp_size[0]/self.__vp_size[1]
proj = glm.perspective(glm.radians(90.0), aspect, 0.1, 10.0)
view = glm.lookAt(glm.vec3(0,-3,0), glm.vec3(0, 0, 0), glm.vec3(0,0,1))
angle1 = self.elapsed_ms() * math.pi * 2 / 5000.0
angle2 = self.elapsed_ms() * math.pi * 2 / 7333.0
model = glm.rotate(model, angle1, glm.vec3(1, 0, 0))
model = glm.rotate(model, angle2, glm.vec3(0, 1, 0))
glUniformMatrix4fv(self.___uniform['u_proj'], 1, GL_FALSE, glm.value_ptr(proj) )
glUniformMatrix4fv(self.___uniform['u_view'], 1, GL_FALSE, glm.value_ptr(view) )
glUniformMatrix4fv(self.___uniform['u_model'], 1, GL_FALSE, glm.value_ptr(model) )
glClearColor(0.2, 0.3, 0.3, 1.0)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
glDrawElements(GL_TRIANGLES, self.__no_indices, GL_UNSIGNED_INT, None)
window = MyWindow(800, 600)
window.run()