Question

当您通过移动鼠标滚轮放大/缩小时，我试图模仿3dsmax行为。在3ds max中，此缩放将朝着鼠标位置移动。到目前为止，我已经提出了这个小mcve：

import math
from ctypes import c_void_p

import numpy as np
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *
from glm import *


class Camera():

    def __init__(
        self,
        eye=None, target=None, up=None,
        fov=None, near=0.1, far=100000,
        **kwargs
    ):
        self.eye = vec3(eye) or vec3(0, 0, 1)
        self.target = vec3(target) or vec3(0, 0, 0)
        self.up = vec3(up) or vec3(0, 1, 0)
        self.original_up = vec3(self.up)
        self.fov = fov or radians(45)
        self.near = near
        self.far = far

    def update(self, aspect):
        self.view = lookAt(self.eye, self.target, self.up)
        self.projection = perspective(self.fov, aspect, self.near, self.far)

    def zoom(self, *args):
        delta = -args[1] * 0.1
        distance = length(self.target - self.eye)
        self.eye = self.target + (self.eye - self.target) * (delta + 1)

    def zoom_towards_cursor(self, *args):
        x = args[2]
        y = args[3]
        v = glGetIntegerv(GL_VIEWPORT)
        viewport = vec4(float(v[0]), float(v[1]), float(v[2]), float(v[3]))
        height = viewport.z

        p0 = vec3(x, height - y, 0.0)
        p1 = vec3(x, height - y, 1.0)
        v1 = unProject(p0, self.view, self.projection, viewport)
        v2 = unProject(p1, self.view, self.projection, viewport)

        world_from = vec3(
            (-v1.z * (v2.x - v1.x)) / (v2.z - v1.z) + v1.x,
            (-v1.z * (v2.y - v1.y)) / (v2.z - v1.z) + v1.y,
            0.0
        )

        self.eye.z = self.eye.z * (1.0 + 0.1 * args[1])

        view = lookAt(self.eye, self.target, self.up)
        v1 = unProject(p0, view, self.projection, viewport)
        v2 = unProject(p1, view, self.projection, viewport)

        world_to = vec3(
            (v1.z * (v2.x - v1.x)) / (v2.z - v1.z) + v1.x,
            (-v1.z * (v2.y - v1.y)) / (v2.z - v1.z) + v1.y,
            0.0
        )

        offset = world_to - world_from
        print(self.eye.z, world_from, world_to, offset)

        self.eye += offset
        self.target += offset


class GlutController():

    def __init__(self, camera):
        self.camera = camera
        self.zoom = self.camera.zoom

    def glut_mouse_wheel(self, *args):
        self.zoom(*args)


class MyWindow:

    def __init__(self, w, h):
        self.width = w
        self.height = h

        glutInit()
        glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH)
        glutInitWindowSize(w, h)
        glutCreateWindow('OpenGL Window')

        self.startup()

        glutReshapeFunc(self.reshape)
        glutDisplayFunc(self.display)
        glutMouseWheelFunc(self.controller.glut_mouse_wheel)
        glutKeyboardFunc(self.keyboard_func)
        glutIdleFunc(self.idle_func)

    def keyboard_func(self, *args):
        try:
            key = args[0].decode("utf8")

            if key == "\x1b":
                glutLeaveMainLoop()

            if key in ['1']:
                self.controller.zoom = self.camera.zoom
                print("Using normal zoom")
            elif key in ['2']:
                self.controller.zoom = self.camera.zoom_towards_cursor
                print("Using zoom towards mouse")

        except Exception as e:
            import traceback
            traceback.print_exc()

    def startup(self):
        glEnable(GL_DEPTH_TEST)

        aspect = self.width / self.height
        params = {
            "eye": vec3(10, 10, 10),
            "target": vec3(0, 0, 0),
            "up": vec3(0, 1, 0)
        }
        self.cameras = [
            Camera(**params)
        ]
        self.camera = self.cameras[0]
        self.model = mat4(1)
        self.controller = GlutController(self.camera)

    def run(self):
        glutMainLoop()

    def idle_func(self):
        glutPostRedisplay()

    def reshape(self, w, h):
        glViewport(0, 0, w, h)
        self.width = w
        self.height = h

    def display(self):
        self.camera.update(self.width / self.height)

        glClearColor(0.2, 0.3, 0.3, 1.0)
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)

        glMatrixMode(GL_PROJECTION)
        glLoadIdentity()
        gluPerspective(degrees(self.camera.fov), self.width / self.height, self.camera.near, self.camera.far)
        glMatrixMode(GL_MODELVIEW)
        glLoadIdentity()
        e = self.camera.eye
        t = self.camera.target
        u = self.camera.up
        gluLookAt(e.x, e.y, e.z, t.x, t.y, t.z, u.x, u.y, u.z)
        glColor3f(1, 1, 1)
        glBegin(GL_LINES)
        for i in range(-5, 6):
            if i == 0:
                continue
            glVertex3f(-5, 0, i)
            glVertex3f(5, 0, i)
            glVertex3f(i, 0, -5)
            glVertex3f(i, 0, 5)
        glEnd()

        glBegin(GL_LINES)
        glColor3f(1, 1, 1)
        glVertex3f(-5, 0, 0)
        glVertex3f(0, 0, 0)
        glVertex3f(0, 0, -5)
        glVertex3f(0, 0, 0)

        glColor3f(1, 0, 0)
        glVertex3f(0, 0, 0)
        glVertex3f(5, 0, 0)
        glColor3f(0, 1, 0)
        glVertex3f(0, 0, 0)
        glVertex3f(0, 5, 0)
        glColor3f(0, 0, 1)
        glVertex3f(0, 0, 0)
        glVertex3f(0, 0, 5)
        glEnd()

        glutSwapBuffers()


if __name__ == '__main__':
    window = MyWindow(800, 600)
    window.run()

在此代码段中，您可以通过按“ 1”或“ 2”键在2种缩放模式之间切换。

按“ 1”时，我正在执行标准缩放，到目前为止效果很好。

问题是当按下'2'时，在这种情况下，我试图将代码从thread改编为python / pyopengl / pygml，但是因为我不太清楚该答案的基本数学原理，不太了解如何解决不良行为。

您将如何修复发布的代码，使其像3dsmax一样正确地放大/缩小鼠标？

Answer 1

一种可能的解决方案是使照相机沿光线从照相机位置移动到光标（鼠标）位置，并平行移动目标位置。

self.eye    = self.eye    + ray_cursor * delta
self.target = self.target + ray_cursor * delta

为此，光标的窗口位置必须为“未投影”（unProject）。

计算光标在世界空间中的位置（例如，在远端平面上）：

pt_wnd   = vec3(x, height - y, 1.0)
pt_world = unProject(pt_wnd, self.view, self.projection, viewport)

从眼睛位置到光标的光线由从眼睛位置到世界空间光标位置的归一化矢量给出：

ray_cursor = normalize(pt_world - self.eye)

从视口矩形获取窗口高度时，代码中存在问题，因为高度是.w组件而不是.z组件：

v = glGetIntegerv(GL_VIEWPORT)
viewport = vec4(float(v[0]), float(v[1]), float(v[2]), float(v[3]))
width  = viewport.z
height = viewport.w

函数zoom_towards_cursor的完整代码清单：

def zoom_towards_cursor(self, *args):
    x = args[2]
    y = args[3]
    v = glGetIntegerv(GL_VIEWPORT)
    viewport = vec4(float(v[0]), float(v[1]), float(v[2]), float(v[3]))
    width  = viewport.z
    height = viewport.w

    pt_wnd     = vec3(x, height - y, 1.0)
    pt_world   = unProject(pt_wnd, self.view, self.projection, viewport)
    ray_cursor = normalize(pt_world - self.eye)

    delta = -args[1]
    self.eye    = self.eye    + ray_cursor * delta
    self.target = self.target + ray_cursor * delta

预览：

如何在3dsMax中实现对鼠标的缩放？

1 个答案: