Difference between revisions of "LlAngleBetween"

From Second Life Wiki
Jump to navigation Jump to search
m
m
 
(10 intermediate revisions by 3 users not shown)
Line 1: Line 1:
{{Issue/SVC-2424}}{{LSL_Function
{{LSL_Function
|inject-2={{Issues/SVC-2424}}
|func_id=174|func_sleep=0.0|func_energy=10.0
|func_id=174|func_sleep=0.0|func_energy=10.0
|func=llAngleBetween|sort=AngleBetween
|func=llAngleBetween|sort=AngleBetween
Line 6: Line 7:
|p2_type=rotation|p2_name=b|p2_desc=end rotation
|p2_type=rotation|p2_name=b|p2_desc=end rotation
|func_footnote
|func_footnote
|return_text=that is the angle between rotation '''a''' and '''b'''.
|return_text=that is the angle in radians between rotation {{LSLP|a}} and rotation {{LSLP|b}}.
|spec
|spec
|caveats
|caveats
|examples
|examples=
<source lang="lsl2">
default
{
    touch_start(integer num_detected)
    {
        rotation currentRootRotation = llGetRootRotation();
        float angle = llAngleBetween(ZERO_ROTATION, currentRootRotation);
 
        // PUBLIC_CHANNEL has the integer value 0
        llSay(PUBLIC_CHANNEL,
            "llAngleBetween(ZERO_ROTATION, " + (string)currentRootRotation + ") = " + (string)angle);
    }
}
</source>
|helpers
|helpers
|also_functions={{LSL DefineRow||[[llRotBetween]]}}
|also_functions={{LSL DefineRow||[[llRotBetween]]}}
Line 17: Line 32:
|also_articles
|also_articles
|notes
|notes
|deepnotes=<lsl>float AngleBetween(rotation a, rotation b)
|deepnotes= ===Reference===
<source lang="lsl2">float AngleBetween(rotation a, rotation b)//simple but turns out to not be very accurate.
{
    return 2.0 * llAcos( llFabs(a.x * b.x + a.y * b.y + a.z * b.z + a.s * b.s)
                      / llSqrt((a.x * a.x + a.y * a.y + a.z * a.z + a.s * a.s)
                            * (b.x * b.x + b.y * b.y + b.z * b.z + b.s * b.s)));
}</source>
 
<source lang="lsl2">float AngleBetween(rotation a, rotation b)//more complex implementation but more accurate, and reasonably fast.
{
{
     return 2.0 * llAcos((a.x * b.x + a.y * b.y + a.z * b.z + a.s * b.s)
     rotation r = b / a; // calculate the rotation between the two arguments as quaternion
              / llSqrt((a.x * a.x + a.y * a.y + a.z * a.z + a.s * a.s)
    float s2 = r.s * r.s; // square of the s-element
                      * (b.x * b.x + b.y * b.y + b.z * b.z + b.s * b.s)));
    float v2 = r.x * r.x + r.y * r.y + r.z * r.z; // sum of the squares of the v-elements
}</lsl>
 
    if (s2 < v2) // compare the s-component to the v-component
        return 2.0 * llAcos(llSqrt(s2 / (s2 + v2))); // use arccos if the v-component is dominant
    if (v2) // make sure the v-component is non-zero
        return 2.0 * llAsin(llSqrt(v2 / (s2 + v2))); // use arcsin if the s-component is dominant
 
    return 0.0; // one or both arguments are scaled too small to be meaningful, or the values are the same, so return zero
}//Written by Moon Metty & Miranda Umino. Minor optimizations by Strife Onizuka</source>
 
Watch for developments on this function with {{Jira|SVC-2424}}
|cat1=Math/3D
|cat1=Math/3D
|cat2
|cat2

Latest revision as of 22:20, 21 January 2015

Summary

Function: float llAngleBetween( rotation a, rotation b );
0.0 Forced Delay
10.0 Energy

Returns a float that is the angle in radians between rotation a and rotation b.

• rotation a – start rotation
• rotation b – end rotation

Examples

default
{
    touch_start(integer num_detected)
    {
        rotation currentRootRotation = llGetRootRotation();
        float angle = llAngleBetween(ZERO_ROTATION, currentRootRotation);

        // PUBLIC_CHANNEL has the integer value 0
        llSay(PUBLIC_CHANNEL,
            "llAngleBetween(ZERO_ROTATION, " + (string)currentRootRotation + ") = " + (string)angle);
    }
}

See Also

Functions

•  llRotBetween
•  llRot2Angle – Similar functionality used for the Axis-Angle format

Deep Notes

Reference

float AngleBetween(rotation a, rotation b)//simple but turns out to not be very accurate.
{
    return 2.0 * llAcos( llFabs(a.x * b.x + a.y * b.y + a.z * b.z + a.s * b.s)
                      / llSqrt((a.x * a.x + a.y * a.y + a.z * a.z + a.s * a.s)
                             * (b.x * b.x + b.y * b.y + b.z * b.z + b.s * b.s)));
}

float AngleBetween(rotation a, rotation b)//more complex implementation but more accurate, and reasonably fast.
{
    rotation r = b / a; // calculate the rotation between the two arguments as quaternion
    float s2 = r.s * r.s; // square of the s-element
    float v2 = r.x * r.x + r.y * r.y + r.z * r.z; // sum of the squares of the v-elements

    if (s2 < v2) // compare the s-component to the v-component
        return 2.0 * llAcos(llSqrt(s2 / (s2 + v2))); // use arccos if the v-component is dominant
    if (v2) // make sure the v-component is non-zero
        return 2.0 * llAsin(llSqrt(v2 / (s2 + v2))); // use arcsin if the s-component is dominant

    return 0.0; // one or both arguments are scaled too small to be meaningful, or the values are the same, so return zero
}//Written by Moon Metty & Miranda Umino. Minor optimizations by Strife Onizuka

Watch for developments on this function with SVC-2424

Signature

function float llAngleBetween( rotation a, rotation b );
Retrieved from "https://wiki.secondlife.com/w/index.php?title=LlAngleBetween&oldid=1194051"