From a58a8296d9da785920575725bbb41fd5481b5d2d Mon Sep 17 00:00:00 2001 From: Henrik Dick Date: Fri, 30 Apr 2021 23:38:31 +1000 Subject: Fix T85470: Simple deform modifier causes artifacts at low angles 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 --- source/blender/modifiers/intern/MOD_simpledeform.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'source/blender/modifiers') diff --git a/source/blender/modifiers/intern/MOD_simpledeform.c b/source/blender/modifiers/intern/MOD_simpledeform.c index ea31bdc6e31..951eacdecda 100644 --- a/source/blender/modifiers/intern/MOD_simpledeform.c +++ b/source/blender/modifiers/intern/MOD_simpledeform.c @@ -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]; -- cgit v1.2.3