我正在尝试以某个角度投影照片。
如果照片是在相机直视前方时拍摄的，则相机角度 ( yaw, pitch, roll) 都为零。
现在让我们说相机有点向上看，假设用pitch=1 radians，那么照片实际上是在捕捉梯形而不是矩形：
现在让我们来看看代码——这是一个简单的程序，它使用moderngl-window 投射没有角度的照片：
import moderngl
import moderngl_window
import numpy as np
from PIL import Image
class Pygame(moderngl_window.WindowConfig):
window_size = 1280, 720
def __init__(self, **kwargs):
super().__init__(**kwargs)
self.program = self.ctx.program(
vertex_shader="""
#version 330
in vec2 vertex_xy;
in vec2 vertex_uv;
uniform mat4 model;
out vec2 fragment_uv;
void main() {
vec4 p = vec4(vertex_xy, 0.0, 1.0);
gl_Position = model * p;
fragment_uv = vertex_uv;
}
""",
fragment_shader="""
#version 330
in vec2 fragment_uv;
uniform sampler2D texture0;
out vec4 fragment_color;
void main() {
fragment_color = texture(texture0, fragment_uv);
}
"""
)
self.program['model'].write(bytes(np.eye(4, dtype=np.float32)))
self.program['texture0'].value = 0
self.vertex_array = self.init_vertex_array(self.ctx, self.program)
image = Image.open('test.jpg').transpose(Image.FLIP_TOP_BOTTOM)
self.texture = self.ctx.texture(image.size, 3, image.tobytes())
self.texture.use()
def render(self, time, frametime):
self.ctx.clear()
self.vertex_array.render()
def init_vertex_array(self, context: moderngl.Context, program: moderngl.Program) -> moderngl.VertexArray:
vertices_xy = self.get_vertices_for_quad_2d(size=(2.0, 2.0), bottom_left_corner=(-1.0, -1.0))
vertex_buffer_xy = context.buffer(vertices_xy.tobytes())
vertices_uv = self.get_vertices_for_quad_2d(size=(1.0, 1.0), bottom_left_corner=(0.0, 0.0))
vertex_buffer_uv = context.buffer(vertices_uv.tobytes())
vertex_array = context.vertex_array(program, [(vertex_buffer_xy, "2f", "vertex_xy"),
(vertex_buffer_uv, "2f", "vertex_uv")])
return vertex_array
def get_vertices_for_quad_2d(self, size=(2.0, 2.0), bottom_left_corner=(-1.0, -1.0)) -> np.array:
# A quad is composed of 2 triangles: https://en.wikipedia.org/wiki/Polygon_mesh
w, h = size
x_bl, y_bl = bottom_left_corner
vertices = np.array([x_bl, y_bl + h,
x_bl, y_bl,
x_bl + w, y_bl,
x_bl, y_bl + h,
x_bl + w, y_bl,
x_bl + w, y_bl + h], dtype=np.float32)
return vertices
if __name__ == '__main__':
moderngl_window.run_window_config(Pygame, args=('--window', 'glfw'))
当你运行这个程序时，你会看到这个窗口：
现在，如果我们编辑render函数以添加角度：
def render(self, time, frametime):
pitch_rad = 1
rotate_around_y_pitch = np.array([[np.cos(pitch_rad), 0, np.sin(pitch_rad), 0],
[0, 1, 0, 0],
[-np.sin(pitch_rad), 0, np.cos(pitch_rad), 0],
[0, 0, 0, 1]], dtype=np.float32)
self.program['model'].write(bytes(rotate_around_y_pitch))
self.ctx.clear()
self.vertex_array.render()
那么投影的照片仍然是矩形的（只是纵横比发生了变化）而不是梯形。
我错过了什么？
