[英]Mapping a texture onto a quad with OpenGL 4, Python, and vertex shaders
我正在嘗試使用現代OpenGL代碼創建一個程序,該程序顯示帶有映射到其上的紋理的QUAD。
應該拉伸紋理以匹配四邊形大小。 現在,紋理重復出現。
如果每個頂點和映射是在代碼中單獨完成的,我已經看到了將紋理映射到四邊形的代碼。 但是,我認為現在應該使用頂點着色器? 使用OpenGL 4.5或其他方法,應該怎么做?
"""
Open a window that displays a quad with an image on it.
"""
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *
from PIL import Image
from math import *
from time import *
class MyApplication:
""" Main application class. """
def __init__(self):
self.vao = 0
def load_texture(self, file_name):
image = Image.open(file_name)
width = image.size[0]
height = image.size[1]
image_bytes = image.convert("RGBA").tobytes ( "raw", "RGBA", 0, -1)
texture = glGenTextures(1)
glBindTexture ( GL_TEXTURE_2D, texture )
glTexParameterf ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT )
glTexParameterf ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT )
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,GL_LINEAR )
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_LINEAR )
gluBuild2DMipmaps ( GL_TEXTURE_2D, GL_RGBA, width, height, GL_RGBA, GL_UNSIGNED_BYTE, image_bytes )
return texture
def compile_shaders(self):
""" Get the shaders ready. """
# Create a triangle with three (x, y, z, ?) points.
vertex_shader_source = """
#version 450 core
void main( void)
{
// Declare a hard-coded array of positions
const vec4 vertices[4] = vec4[4](vec4(-0.5, 0.5, 0.5, 1.0),
vec4( 0.5, 0.5, 0.5, 1.0),
vec4( 0.5, -0.5, 0.5, 1.0),
vec4(-0.5, -0.5, 0.5, 1.0));
// Index into our array using gl_VertexID
gl_Position = vertices[gl_VertexID];
}
"""
vertex_shader = glCreateShader(GL_VERTEX_SHADER)
glShaderSource(vertex_shader, vertex_shader_source)
glCompileShader(vertex_shader)
# Specify the color of our fragment (RGBA)
texture = self.load_texture("test_ship.png")
fragment_shader_source = """
#version 450 core
uniform sampler2D s;
out vec4 color;
void main(void)
{
color = texture(s, gl_FragCoord.xy / textureSize(s, 0));
}
"""
fragment_shader = glCreateShader(GL_FRAGMENT_SHADER)
glShaderSource(fragment_shader, fragment_shader_source)
glCompileShader(fragment_shader)
# --- Create a program
program = glCreateProgram()
glAttachShader(program, vertex_shader)
glAttachShader(program, fragment_shader)
glLinkProgram(program)
glGenVertexArrays(1, self.vao)
glBindVertexArray(self.vao)
# --- Clean up now that we don't need these shaders anymore.
glDeleteShader(vertex_shader)
glDeleteShader(fragment_shader)
return program
def startup(self):
self.rendering_program = self.compile_shaders()
self.vertex_array_object = GLuint()
glCreateVertexArrays(1, self.vertex_array_object)
def render(self):
# Support transparency
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
# Get a color based on the time
color = (sin(time()), cos(time()), 0)
# Clear the screen
glClearBufferfv(GL_COLOR, 0, color)
# Tell the computer what to render
glUseProgram(self.rendering_program)
glDrawArrays(GL_QUADS, 0, 4)
# Display
glutSwapBuffers()
def animate(self):
glutPostRedisplay()
def run(self):
glutInit(sys.argv)
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH)
glutInitWindowSize(500, 500)
glutInitWindowPosition(0, 0)
glutCreateWindow(b"Simple PyOpenGL example")
self.startup()
glutIdleFunc(self.animate)
glutDisplayFunc(self.render)
glutMainLoop()
my_application = MyApplication()
my_application.run()
我相信這里有兩個問題:
1)如果看到重復的圖案,則根據當前的WRAP_S和WRAP_T設置,可以認為您的UV坐標錯誤。
在片段着色器中,可以使用以下計算獲得UV坐標:
color = texture(s, gl_FragCoord.xy / textureSize(s, 0));
但是,從四邊形坐標來看,這不會映射到紋理坐標所需的[0,1]間隔。 (如果它低於或超過此間隔,則將得到該值的模)。
2)如果您不想重復,請使用以下命令:
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE)
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