真等角投影用OpenGL
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21-08-2019 - |
题
我在OpenGL编程新手用C ++,并在数学不是很好。有一个简单的办法有等角投影?
我的意思是真实等角投影时,不是一般的正交投影。
(等角投影只发生在单元X的突起,Y和Z的载体是等长的并在它们之间的角度是完全120度。)
代码段的高度赞赏..
解决方案
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();
结果
我们可以得出一个立方体,以检查平行线确实平行
glPushMatrix();
glTranslated(0.5, 0.5, 0.5);
glColor3d(0.5, 0.5, 0.5);
glutWireCube(1);
glPopMatrix();
其他提示
这是等角投影仅仅是一个使用正交投影与特定旋转角度的问题。
您应该能够选择任何8个潜在的方位,用正投影,并得到你的模型的完善等轴测图。只要按照数学在建立视图矩阵的引用维基文章,并为您的投影矩阵做正交投影,和你所有的设置。
也许我不是很正确所著的Grokking数学,但不能你只是定位你的相机,因为它在维基百科的链接解释和使用标准正交投影?
即使它不一样,投影堆栈完全取决于你。
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// your isometric matrix here (see math on Wikipedia)
glMatrixMode(GL_MODELVIEW);
如果你不想使用GLU,这里是用glOrtho梗概
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);
}
和调用这样的
gl_enter_2_5d_mode()
test()
gl_leave_2_5d_mode()
如果您想在2D与2.5D之间切换(所以你可以画出你的UI),那么我也有类似的功能,进入和离开2D模式e.g。
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();
}
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