shmup/ants
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Fix gravity logic and revert y-flip

Browse source
This commit is contained in:
Jared Miller 2026-03-11 15:10:36 -04:00
parent 7003e074c5
commit 37d615e87a
Signed by: shmup
GPG key ID: 22B5C6D66A38B06C
1 changed files with 36 additions and 40 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

76
src/shaders/sandPhysics.frag
View file

@ -32,11 +32,14 @@ void main() {
}
// read 2x2 block
// index mapping (GL coords — Y increases upward):
// [2][3] <- top row (y offset 1, higher Y)
// [0][1] <- bottom row (y offset 0, lower Y)
vec4 cells[4];
float behaviors[4];
float densities[4];
for (int i = 0; i < 4; i++) {
ivec2 p = blockBase + ivec2(i % 2, 1 - i / 2);
ivec2 p = blockBase + ivec2(i % 2, i / 2);
cells[i] = texelFetch(uWorld, p, 0);
vec4 props = texelFetch(uMaterialProps, ivec2(int(cells[i].r), 0), 0);
behaviors[i] = props.r;
@ -44,22 +47,17 @@ void main() {
}
// capture blocked state before vertical swaps modify the arrays
bool col0Blocked = (behaviors[0] == BEHAVIOR_SOLID || behaviors[2] == BEHAVIOR_SOLID || densities[0] <= densities[2]);
bool col1Blocked = (behaviors[1] == BEHAVIOR_SOLID || behaviors[3] == BEHAVIOR_SOLID || densities[1] <= densities[3]);
// "blocked" = column is settled (top lighter/equal to bottom) or contains solid
bool col0Blocked = (behaviors[0] == BEHAVIOR_SOLID || behaviors[2] == BEHAVIOR_SOLID || densities[2] <= densities[0]);
bool col1Blocked = (behaviors[1] == BEHAVIOR_SOLID || behaviors[3] == BEHAVIOR_SOLID || densities[3] <= densities[1]);
// random seed for this block this frame
uint seed = hash(uint(blockBase.x) * 7919u + uint(blockBase.y) * 6271u + uint(uFrame) * 3571u);
// try vertical gravity: column 0 (indices 0, 2) and column 1 (indices 1, 3)
// top=0,1 bottom=2,3
// block layout:
// [0][1] <- top row
// [2][3] <- bottom row
// if top is movable and top.density > bottom.density, swap
// vertical gravity: top cells (2,3) fall to bottom (0,1) if heavier
for (int col = 0; col < 2; col++) {
int top = col; // 0 or 1
int bot = col + 2; // 2 or 3
int top = col + 2; // 2 or 3 — top row (higher Y)
int bot = col; // 0 or 1 — bottom row (lower Y)
if (behaviors[top] != BEHAVIOR_SOLID && behaviors[bot] != BEHAVIOR_SOLID) {
if (densities[top] > densities[bot]) {
@ -74,41 +72,39 @@ void main() {
}
}
// try diagonal: if top cell still has high density and couldn't fall straight
// for top-left (0): can it go diagonal to bottom-right (3)?
// for top-right (1): can it go diagonal to bottom-left (2)?
// only if the cell directly below is blocked (same or higher density)
// diagonal: if a top cell couldn't fall straight down, try diagonal
// top-left (2) -> bottom-right (1), top-right (3) -> bottom-left (0)
bool tryLeftFirst = (seed & 1u) == 0u;
if (tryLeftFirst) {
// try 0->3 diagonal (top-left to bottom-right)
if (col0Blocked && behaviors[0] != BEHAVIOR_SOLID && behaviors[3] != BEHAVIOR_SOLID &&
densities[0] > densities[3]) {
vec4 tmp = cells[0]; cells[0] = cells[3]; cells[3] = tmp;
float tmpB = behaviors[0]; behaviors[0] = behaviors[3]; behaviors[3] = tmpB;
float tmpD = densities[0]; densities[0] = densities[3]; densities[3] = tmpD;
// try 2->1 diagonal (top-left to bottom-right)
if (col0Blocked && behaviors[2] != BEHAVIOR_SOLID && behaviors[1] != BEHAVIOR_SOLID &&
densities[2] > densities[1]) {
vec4 tmp = cells[2]; cells[2] = cells[1]; cells[1] = tmp;
float tmpB = behaviors[2]; behaviors[2] = behaviors[1]; behaviors[1] = tmpB;
float tmpD = densities[2]; densities[2] = densities[1]; densities[1] = tmpD;
}
// try 1->2 diagonal (top-right to bottom-left)
if (col1Blocked && behaviors[1] != BEHAVIOR_SOLID && behaviors[2] != BEHAVIOR_SOLID &&
densities[1] > densities[2]) {
vec4 tmp = cells[1]; cells[1] = cells[2]; cells[2] = tmp;
float tmpB = behaviors[1]; behaviors[1] = behaviors[2]; behaviors[2] = tmpB;
float tmpD = densities[1]; densities[1] = densities[2]; densities[2] = tmpD;
// try 3->0 diagonal (top-right to bottom-left)
if (col1Blocked && behaviors[3] != BEHAVIOR_SOLID && behaviors[0] != BEHAVIOR_SOLID &&
densities[3] > densities[0]) {
vec4 tmp = cells[3]; cells[3] = cells[0]; cells[0] = tmp;
float tmpB = behaviors[3]; behaviors[3] = behaviors[0]; behaviors[0] = tmpB;
float tmpD = densities[3]; densities[3] = densities[0]; densities[0] = tmpD;
}
} else {
// try 1->2 first
if (col1Blocked && behaviors[1] != BEHAVIOR_SOLID && behaviors[2] != BEHAVIOR_SOLID &&
densities[1] > densities[2]) {
vec4 tmp = cells[1]; cells[1] = cells[2]; cells[2] = tmp;
float tmpB = behaviors[1]; behaviors[1] = behaviors[2]; behaviors[2] = tmpB;
float tmpD = densities[1]; densities[1] = densities[2]; densities[2] = tmpD;
// try 3->0 first
if (col1Blocked && behaviors[3] != BEHAVIOR_SOLID && behaviors[0] != BEHAVIOR_SOLID &&
densities[3] > densities[0]) {
vec4 tmp = cells[3]; cells[3] = cells[0]; cells[0] = tmp;
float tmpB = behaviors[3]; behaviors[3] = behaviors[0]; behaviors[0] = tmpB;
float tmpD = densities[3]; densities[3] = densities[0]; densities[0] = tmpD;
}
// try 0->3
if (col0Blocked && behaviors[0] != BEHAVIOR_SOLID && behaviors[3] != BEHAVIOR_SOLID &&
densities[0] > densities[3]) {
vec4 tmp = cells[0]; cells[0] = cells[3]; cells[3] = tmp;
float tmpB = behaviors[0]; behaviors[0] = behaviors[3]; behaviors[3] = tmpB;
float tmpD = densities[0]; densities[0] = densities[3]; densities[3] = tmpD;
// try 2->1
if (col0Blocked && behaviors[2] != BEHAVIOR_SOLID && behaviors[1] != BEHAVIOR_SOLID &&
densities[2] > densities[1]) {
vec4 tmp = cells[2]; cells[2] = cells[1]; cells[1] = tmp;
float tmpB = behaviors[2]; behaviors[2] = behaviors[1]; behaviors[1] = tmpB;
float tmpD = densities[2]; densities[2] = densities[1]; densities[1] = tmpD;
}
}