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Factor out rotation matrix

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Grant Sanderson 2023-01-19 10:47:21 -08:00
parent 1eae7c06ba
commit c873d073e2
1 changed files with 21 additions and 21 deletions
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42
manimlib/shaders/inserts/get_xyz_to_uv.glsl
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@ -38,35 +38,35 @@ mat4 map_triangles(vec3 src0, vec3 src1, vec3 src2, vec3 dst0, vec3 dst1, vec3 d
}
mat4 rotation(vec3 axis, float cos_angle){
float c = cos_angle;
float s = sqrt(1 - c * c); // Sine of the angle
float oc = 1.0 - c;
float ax = axis.x;
float ay = axis.y;
float az = axis.z;
return mat4(
oc * ax * ax + c, oc * ax * ay + az * s, oc * az * ax - ay * s, 0.0,
oc * ax * ay - az * s, oc * ay * ay + c, oc * ay * az + ax * s, 0.0,
oc * az * ax + ay * s, oc * ay * az - ax * s, oc * az * az + c, 0.0,
0.0, 0.0, 0.0, 1.0
);
}
mat4 map_onto_x_axis(vec3 src0, vec3 src1){
mat4 shift = mat4(1.0);
shift[3].xyz = -src0;
// Find rotation matrix between unit vectors in each direction
vec3 vect = normalize(src1 - src0);
// This is the same as cross(vect, vec3(1, 0, 0))
vec3 axis = vec3(0.0, vect.z, -vect.y);
float s = length(axis); // Sine of the angle between them
float c = vect.x; // Cosine of the angle between them
// No rotation needed
if(s < 1e-8) return shift;
axis = axis / s; // Axis of rotation
float oc = 1.0 - c;
float ax = axis.x;
float ay = axis.y;
float az = axis.z;
// Rotation matrix about axis, with a given angle corresponding to s and c.
mat4 rotate = mat4(
oc * ax * ax + c, oc * ax * ay + az * s, oc * az * ax - ay * s, 0.0,
oc * ax * ay - az * s, oc * ay * ay + c, oc * ay * az + ax * s, 0.0,
oc * az * ax + ay * s, oc * ay * az - ax * s, oc * az * az + c, 0.0,
0.0, 0.0, 0.0, 1.0
);
if(vect.x > 1 - 1e-6) return shift;
// Equivalent to cross(vect, vec3(1, 0, 0))
vec3 axis = vec3(0.0, vect.z, -vect.y);
mat4 rotate = rotation(normalize(axis), vect.x);
return rotate * shift;
}