i am working on a 3d-engine and i want to use an "up"-vector and a "heading"- or "center"-vector as indicators for the rotated-Position of an 3d-object. To create a rotation-matrix for the OpenGL-shaders GLM provides the function rotate(mat4(), radians, axis_of_rotation). However, because i don't keep track of the axis_of_rotation nor how many radians a 3d-object is rotated, i can't use this function directly. Currently i am using a custom function that looks like this:
我正在研究一个3D引擎,我想使用“向上” - 矢量和“标题” - 或“中心” - 矢量作为3d对象的旋转位置的指示器。要为OpenGL着色器创建旋转矩阵,GLM提供函数rotate(mat4(),radians,axis_of_rotation)。但是,因为我没有跟踪axis_of_rotation,也没有跟踪旋转3d对象的弧度,我不能直接使用此函数。目前我使用的自定义函数如下所示:
mat4 altRotate(vec3 center, vec3 up) {
GLfloat alpha_y = acos(dot(normalize(vec2(center.z, center.x)), vec2(1.0f, 0.0f)));
if (center.x < 0.0f)
alpha_y = -alpha_y;
mat4 Ry = {
cos(alpha_y), 0, sin(alpha_y), 0,
0, 1, 0, 0,
-sin(alpha_y), 0, cos(alpha_y), 0,
0, 0, 0, 1
};
center = vec3(Ry * vec4(center, 1.0f));
up = vec3(Ry * vec4(up, 1.0f));
GLfloat alpha_x = acos(dot(normalize(vec2(center.z, center.y)), vec2(1.0f, 0.0f)));
if (center.y > 0.0f)
alpha_x = -alpha_x;
mat4 Rx = {
1, 0, 0, 0,
0, cos(alpha_x), -sin(alpha_x), 0,
0, sin(alpha_x), cos(alpha_x), 0,
0, 0, 0, 1
};
center = vec3(Rx * vec4(center, 1.0f));
up = vec3(Rx * vec4(up, 1.0f));
GLfloat alpha_z = acos(dot(normalize(vec2(up.y, up.x)), vec2(1.0f, 0.0f)));
if (up.x < 0.0f)
alpha_z = -alpha_z;
mat4 Rz = {
cos(alpha_z), -sin(alpha_z), 0, 0,
sin(alpha_z), cos(alpha_z), 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
};
return Ry * Rx * Rz;
}
However, although i think i could improve the efficiency of this function, i have the feeling that the idea is way to unefficient for a 3d-game-engine. I tried to understand the lookAt-function because what it does seems similar to my function but i didn't understand the code:
然而,虽然我认为我可以提高这个功能的效率,但我觉得这个想法对于3D游戏引擎而言是无效的。我试图理解lookAt函数,因为它看起来与我的函数类似但我不理解代码:
template <typename T, precision P>
GLM_FUNC_QUALIFIER tmat4x4<T, P> lookAtRH
(
tvec3<T, P> const & eye,
tvec3<T, P> const & center,
tvec3<T, P> const & up
)
{
tvec3<T, P> const f(normalize(center - eye));
tvec3<T, P> const s(normalize(cross(f, up)));
tvec3<T, P> const u(cross(s, f));
tmat4x4<T, P> Result(1);
Result[0][0] = s.x;
Result[1][0] = s.y;
Result[2][0] = s.z;
Result[0][1] = u.x;
Result[1][1] = u.y;
Result[2][1] = u.z;
Result[0][2] =-f.x;
Result[1][2] =-f.y;
Result[2][2] =-f.z;
Result[3][0] =-dot(s, eye);
Result[3][1] =-dot(u, eye);
Result[3][2] = dot(f, eye);
return Result;
}
My question is if there is already a function that can create a mat4 that rotates the vec3 (0.0, 0.0, 1.0) to heading and vec3 (0.0, 1.0, 0.0) to up or is there at least a more efficient way to do this?
我的问题是,是否已经有一个函数可以创建一个mat4,它将vec3(0.0,0.0,1.0)旋转到heading和vec3(0.0,1.0,0.0)为up或至少有一种更有效的方法来执行此操作?
1 个解决方案
#1
0
Ok, my solution is to use the lookAt-code by GLM but remove the lins
好的,我的解决方案是使用GLM的lookAt-code但删除lins
Result[3][0] =-dot(s, eye);
Result[3][1] =-dot(u, eye);
Result[3][2] = dot(f, eye);
and to remove the eye / (position) argument. Works fine. The output will be the same as lookat(vec3(0.0f, 0.0f, 0.0f), center, up).
并删除眼睛/(位置)参数。工作良好。输出与lookat相同(vec3(0.0f,0.0f,0.0f),center,up)。
#1
0
Ok, my solution is to use the lookAt-code by GLM but remove the lins
好的,我的解决方案是使用GLM的lookAt-code但删除lins
Result[3][0] =-dot(s, eye);
Result[3][1] =-dot(u, eye);
Result[3][2] = dot(f, eye);
and to remove the eye / (position) argument. Works fine. The output will be the same as lookat(vec3(0.0f, 0.0f, 0.0f), center, up).
并删除眼睛/(位置)参数。工作良好。输出与lookat相同(vec3(0.0f,0.0f,0.0f),center,up)。