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Fix T85470: Simple deform modifier causes artifacts at low angles

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The formula used to compute the bend did subtraction of two big numbers
to get the position. Changed to find the delta and add that,
by rearranging the formula into a more numerically stable form.

Reviewed By: mano-wii, campbellbarton

Ref D11074
This commit is contained in:
Henrik Dick
2021-04-30 23:38:31 +10:00
committed by Campbell Barton
parent 0d07cfd940
commit a58a8296d9
1 changed files with 5 additions and 3 deletions
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8
source/blender/modifiers/intern/MOD_simpledeform.c
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@@ -170,10 +170,12 @@ static void simpleDeform_bend(const float factor,
sint = sinf(theta);
cost = cosf(theta);
/* NOTE: the operations below a susceptible to float precision errors
* regarding the order of operations, take care when changing, see: T85470 */
switch (axis) {
case 0:
r_co[0] = x;
r_co[1] = (y - 1.0f / factor) * cost + 1.0f / factor;
r_co[1] = y * cost + (1.0f - cost) / factor;
r_co[2] = -(y - 1.0f / factor) * sint;
{
r_co[0] += dcut[0];
@@ -182,7 +184,7 @@ static void simpleDeform_bend(const float factor,
}
break;
case 1:
r_co[0] = (x - 1.0f / factor) * cost + 1.0f / factor;
r_co[0] = x * cost + (1.0f - cost) / factor;
r_co[1] = y;
r_co[2] = -(x - 1.0f / factor) * sint;
{
@@ -193,7 +195,7 @@ static void simpleDeform_bend(const float factor,
break;
default:
r_co[0] = -(y - 1.0f / factor) * sint;
r_co[1] = (y - 1.0f / factor) * cost + 1.0f / factor;
r_co[1] = y * cost + (1.0f - cost) / factor;
r_co[2] = z;
{
r_co[0] += cost * dcut[0];