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Optimize Damping Coefficient (#444)

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* Optimize Damping Coefficient

* Added Rounding + Moved Constants

* Added Comments and Made Rounding not use a magic number

* adjust epsilon

* Adjusted Documentation
This commit is contained in:
Elliot Tester
2026-04-23 19:17:23 +03:00
committed by GitHub
parent a3ef7b1493
commit 35b6169fd7
1 changed files with 19 additions and 5 deletions
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source/sprite.c
+19 -5
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@@ -11,6 +11,14 @@
#include <tonc.h> #include <tonc.h>
#include <tonc_oam.h> #include <tonc_oam.h>
// Damping Constants: SPRING_DAMP_NUMERATOR/2^SPRING_DAMP_DENOM_SHIFT ~ 0.699 damping factor
//
// SPRING_DAMP_ROUNDING = 2^(SPRING_DAMP_DENOM_SHIFT - 1) rounding for fixed-point arithmetic by
// adding half the denominator to round instead of truncating
#define SPRING_DAMP_NUMERATOR 179
#define SPRING_DAMP_DENOM_SHIFT 8
#define SPRING_DAMP_ROUNDING (1 << (SPRING_DAMP_DENOM_SHIFT - 1))
OBJ_ATTR obj_buffer[MAX_SPRITES]; OBJ_ATTR obj_buffer[MAX_SPRITES];
OBJ_AFFINE* obj_aff_buffer = (OBJ_AFFINE*)obj_buffer; OBJ_AFFINE* obj_aff_buffer = (OBJ_AFFINE*)obj_buffer;
@@ -211,7 +219,7 @@ void sprite_object_update(SpriteObject* sprite_object)
sprite_object->vrotation += (sprite_object->trotation - sprite_object->rotation) / 8; sprite_object->vrotation += (sprite_object->trotation - sprite_object->rotation) / 8;
// set velocity to 0 if it's close enough to the target // set velocity to 0 if it's close enough to the target
const FIXED epsilon = float2fx(0.01f); const FIXED epsilon = (FIX_ONE >> 6); // = 1/2^6 = 0.015625
if (sprite_object->vx < epsilon && sprite_object->vx > -epsilon && if (sprite_object->vx < epsilon && sprite_object->vx > -epsilon &&
sprite_object->vy < epsilon && sprite_object->vy > -epsilon) sprite_object->vy < epsilon && sprite_object->vy > -epsilon)
{ {
@@ -223,8 +231,10 @@ void sprite_object_update(SpriteObject* sprite_object)
} }
else else
{ {
sprite_object->vx = (sprite_object->vx * 7) / 10; sprite_object->vx = (sprite_object->vx * SPRING_DAMP_NUMERATOR + SPRING_DAMP_ROUNDING) >>
sprite_object->vy = (sprite_object->vy * 7) / 10; SPRING_DAMP_DENOM_SHIFT;
sprite_object->vy = (sprite_object->vy * SPRING_DAMP_NUMERATOR + SPRING_DAMP_ROUNDING) >>
SPRING_DAMP_DENOM_SHIFT;
sprite_object->x += sprite_object->vx; sprite_object->x += sprite_object->vx;
sprite_object->y += sprite_object->vy; sprite_object->y += sprite_object->vy;
@@ -238,7 +248,9 @@ void sprite_object_update(SpriteObject* sprite_object)
} }
else else
{ {
sprite_object->vscale = (sprite_object->vscale * 7) / 10; sprite_object->vscale =
(sprite_object->vscale * SPRING_DAMP_NUMERATOR + SPRING_DAMP_ROUNDING) >>
SPRING_DAMP_DENOM_SHIFT;
sprite_object->scale += sprite_object->vscale; sprite_object->scale += sprite_object->vscale;
} }
@@ -251,7 +263,9 @@ void sprite_object_update(SpriteObject* sprite_object)
} }
else else
{ {
sprite_object->vrotation = (sprite_object->vrotation * 7) / 10; sprite_object->vrotation =
(sprite_object->vrotation * SPRING_DAMP_NUMERATOR + SPRING_DAMP_ROUNDING) >>
SPRING_DAMP_DENOM_SHIFT;
sprite_object->rotation += sprite_object->vrotation; sprite_object->rotation += sprite_object->vrotation;
} }