Commit: e2cb81aa51281df363606382a82aaa06430e3788
Author: Gaia Clary
Date: Sat Nov 21 13:28:44 2020 +0300
Branches: temp-angavrilov-roll-precision
https://developer.blender.org/rBe2cb81aa51281df363606382a82aaa06430e3788
Fix T82455: vec_roll_to_mat3_normalized returns NaN when nor close to -Y.
In this case theta is completely unsafe to use, so a different
threshold based on x and z has to be used to avoid division by zero.
Ref D9551
===================================================================
M source/blender/blenkernel/intern/armature.c
===================================================================
diff --git a/source/blender/blenkernel/intern/armature.c
b/source/blender/blenkernel/intern/armature.c
index e8a3db11219..d05a3611508 100644
--- a/source/blender/blenkernel/intern/armature.c
+++ b/source/blender/blenkernel/intern/armature.c
@@ -2240,15 +2240,16 @@ void mat3_vec_to_roll(const float mat[3][3], const
float vec[3], float *r_roll)
*/
void vec_roll_to_mat3_normalized(const float nor[3], const float roll, float
r_mat[3][3])
{
- const float THETA_SAFE = 1.0e-5f; /* theta above this value are always
safe to use. */
- const float THETA_CRITICAL = 1.0e-9f; /* above this is safe under certain
conditions. */
+ const float SAFE_THRESHOLD = 1.0e-5f; /* theta above this value has good
enough precision. */
+ const float CRITICAL_THRESHOLD = 1.0e-9f; /* above this is safe under
certain conditions. */
+ const float THRESHOLD_SQUARED = CRITICAL_THRESHOLD * CRITICAL_THRESHOLD;
const float x = nor[0];
const float y = nor[1];
const float z = nor[2];
- const float theta = 1.0f + y;
- const float theta_alt = x * x + z * z;
+ const float theta = 1.0f + y; /* remapping Y from [-1,+1] to [0,2].
*/
+ const float theta_alt = x * x + z * z; /* Helper value for matrix
calculations.*/
float rMatrix[3][3], bMatrix[3][3];
BLI_ASSERT_UNIT_V3(nor);
@@ -2258,10 +2259,8 @@ void vec_roll_to_mat3_normalized(const float nor[3],
const float roll, float r_m
* Also, due to float precision errors, nor can be (0.0, -0.99999994, 0.0)
which results
* in theta being close to zero. This will cause problems when theta is used
as divisor.
*/
- if (theta > THETA_SAFE || ((x || z) && theta > THETA_CRITICAL)) {
- /* nor is *not* aligned to negative Y-axis (0,-1,0).
- * We got these values for free... so be happy with it... ;)
- */
+ if (theta > SAFE_THRESHOLD || (theta > CRITICAL_THRESHOLD && theta_alt >
THRESHOLD_SQUARED)) {
+ /* nor is *not* aligned to negative Y-axis (0,-1,0). */
bMatrix[0][1] = -x;
bMatrix[1][0] = x;
@@ -2269,7 +2268,7 @@ void vec_roll_to_mat3_normalized(const float nor[3],
const float roll, float r_m
bMatrix[1][2] = z;
bMatrix[2][1] = -z;
- if (theta > THETA_SAFE) {
+ if (theta > SAFE_THRESHOLD) {
/* nor differs significantly from negative Y axis (0,-1,0): apply the
general case. */
bMatrix[0][0] = 1 - x * x / theta;
bMatrix[2][2] = 1 - z * z / theta;
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