C++ 使用 opengl 进行真正的等距投影
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/1059200/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
true isometric projection with opengl
提问by someone
I am a newbie in OpenGL programming with C++ and not very good at mathematics. Is there a simple way to have isometric projection?
我是使用 C++ 进行 OpenGL 编程的新手，数学不太好。有没有一种简单的方法来进行等距投影？
I mean the true isometric projection, not the general orthogonal projection.
我的意思是真正的等距投影，而不是一般的正交投影。
(Isometric projection happens only when projections of unit X, Y and Z vectors are equally long and angles between them are exactly 120 degrees.)
（等距投影仅在单位 X、Y 和 Z 向量的投影等长且它们之间的角度正好为 120 度时发生。）
Code snippets are highly appreciated..
高度赞赏代码片段..
回答by cobbal
Try using gluLookAt
尝试使用gluLookAt
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
/* use this length so that camera is 1 unit away from origin */
double dist = sqrt(1 / 3.0);
gluLookAt(dist, dist, dist, /* position of camera */
0.0, 0.0, 0.0, /* where camera is pointing at */
0.0, 1.0, 0.0); /* which direction is up */
glMatrixMode(GL_MODELVIEW);
glBegin(GL_LINES);
glColor3d(1.0, 0.0, 0.0);
glVertex3d(0.0, 0.0, 0.0);
glVertex3d(1.0, 0.0, 0.0);
glColor3d(0.0, 1.0, 0.0);
glVertex3d(0.0, 0.0, 0.0);
glVertex3d(0.0, 1.0, 0.0);
glColor3d(0.0, 0.0, 1.0);
glVertex3d(0.0, 0.0, 0.0);
glVertex3d(0.0, 0.0, 1.0);
glEnd();
glFlush();
Results in
结果是
We can draw a cube to check that parallel lines are indeed parallel
我们可以画一个立方体来检查平行线是否确实平行
glPushMatrix();
glTranslated(0.5, 0.5, 0.5);
glColor3d(0.5, 0.5, 0.5);
glutWireCube(1);
glPopMatrix();
回答by Reed Copsey
An isometric projection is just a matter of using an orthographic projection with a specific rotation angle.
等距投影只是使用具有特定旋转角度的正交投影的问题。
You should be able to choose any of the 8 potential orientations, with a orthographic projection, and get a perfect isometric view of your model. Just follow the math in your referenced Wiki article for setting up the view matrix, and do an orthographic projection for your projection matrix, and you're all set.
您应该能够选择 8 个潜在方向中的任何一个，使用正交投影，并获得模型的完美等距视图。只需按照您引用的 Wiki 文章中的数学方法设置视图矩阵，并为您的投影矩阵进行正交投影，就可以了。
回答by Bob Somers
Maybe I'm not quite grokking the math correctly, but couldn't you just position your camera as it explains in that Wikipedia link and use a standard orthogonal projection?
也许我不太正确地理解数学，但是你不能像维基百科链接中解释的那样定位你的相机并使用标准的正交投影吗？
Even if it's not the same, the projection stack is entirely up to you.
即使不一样，投影堆栈也完全取决于您。
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// your isometric matrix here (see math on Wikipedia)
glMatrixMode(GL_MODELVIEW);
回答by Neil McGill
If you do not want to use GLU, here is bare bones using glOrtho
如果您不想使用 GLU，这里是使用 glOrtho 的裸骨
void gl_enter_2_5d_mode (void)
{
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
double scale = 50;
glOrtho(-scale,
scale,
-scale * 0.7,
scale * 0.7,
-scale,
scale);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
glRotatef(35.264f, 1.0f, 0.0f, 0.0f);
glRotatef(-45.0f, 0.0f, 1.0f, 0.0f);
}
void gl_leave_2_5d_mode (void)
{
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
}
then draw a cube in it
void cube (double size)
{
glBegin(GL_QUADS);
glVertex3f(size,size,size);
glVertex3f(-size,size,size);
glVertex3f(-size,-size,size);
glVertex3f(size,-size,size);
glVertex3f(size,size,-size);
glVertex3f(-size,size,-size);
glVertex3f(-size,-size,-size);
glVertex3f(size,-size,-size);
glVertex3f(size,size,size);
glVertex3f(size,-size,size);
glVertex3f(size,-size,-size);
glVertex3f(size,size,-size);
glVertex3f(-size,size,size);
glVertex3f(-size,-size,size);
glVertex3f(-size,-size,-size);
glVertex3f(-size,size,-size);
glVertex3f(size,size,size);
glVertex3f(-size,size,size);
glVertex3f(-size,size,-size);
glVertex3f(size,size,-size);
glVertex3f(size,-size,size);
glVertex3f(-size,-size,size);
glVertex3f(-size,-size,-size);
glVertex3f(size,-size,-size);
glEnd();
}
void test (void)
{
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glBindTexture(GL_TEXTURE_2D, 0);
cube(1.0);
glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);
}
and call something like this
并调用这样的东西
gl_enter_2_5d_mode()
test()
gl_leave_2_5d_mode()
should you want to toggle between 2d and 2.5d (so you can draw your UI) then I have similar functions to enter and leave 2d mode e.g.
如果您想在 2d 和 2.5d 之间切换（以便您可以绘制 UI），那么我有类似的功能可以进入和离开 2d 模式，例如
void gl_init_2d_mode (void)
{
/*
* Enable Texture Mapping
*/
glEnable(GL_TEXTURE_2D);
/*
* Enable alpha blending for sprites
*/
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
/*
* Setup our viewport
*/
glViewport(0, 0, game.video_pix_width,
game.video_pix_height);
/*
* Make sure we're changing the model view and not the projection
*/
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
/*
* Reset the view
*/
glLoadIdentity();
gl_init_fbo();
}
void gl_enter_2d_mode (void)
{
/*
* Change to the projection matrix and set our viewing volume.
*/
glMatrixMode(GL_PROJECTION);
glPushMatrix();
/*
* Reset the view
*/
glLoadIdentity();
/*
* 2D projection
*/
glOrtho(0,
game.video_gl_width, game.video_gl_height,
0, -1200.0, 1200.0);
/*
* Make sure we're changing the model view and not the projection
*/
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
/*
* Reset the view
*/
glLoadIdentity();
}
