112 lines
4.5 KiB
GLSL
112 lines
4.5 KiB
GLSL
precision highp float;
|
|
precision highp int;
|
|
|
|
in vec2 vUv;
|
|
|
|
uniform sampler2D uWorld;
|
|
uniform sampler2D uMaterialProps;
|
|
uniform vec2 uBlockOffset;
|
|
uniform int uFrame;
|
|
|
|
out vec4 fragColor;
|
|
|
|
uint hash(uint x) {
|
|
x ^= x >> 16u;
|
|
x *= 0x45d9f3bu;
|
|
x ^= x >> 16u;
|
|
return x;
|
|
}
|
|
|
|
void main() {
|
|
ivec2 pixel = ivec2(gl_FragCoord.xy);
|
|
ivec2 blockBase = ((pixel - ivec2(uBlockOffset)) / 2) * 2 + ivec2(uBlockOffset);
|
|
ivec2 localPos = pixel - blockBase;
|
|
int localIndex = localPos.x + localPos.y * 2;
|
|
|
|
// bounds check
|
|
int worldSize = int(WORLD_SIZE);
|
|
if (blockBase.x < 0 || blockBase.y < 0 ||
|
|
blockBase.x + 1 >= worldSize || blockBase.y + 1 >= worldSize) {
|
|
fragColor = texelFetch(uWorld, pixel, 0);
|
|
return;
|
|
}
|
|
|
|
// 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, i / 2);
|
|
cells[i] = texelFetch(uWorld, p, 0);
|
|
vec4 props = texelFetch(uMaterialProps, ivec2(int(cells[i].r), 0), 0);
|
|
behaviors[i] = props.r;
|
|
densities[i] = props.g;
|
|
}
|
|
|
|
// capture blocked state before vertical swaps modify the arrays
|
|
// "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);
|
|
|
|
// vertical gravity: top cells (2,3) fall to bottom (0,1) if heavier
|
|
for (int col = 0; col < 2; col++) {
|
|
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]) {
|
|
// swap entire vec4
|
|
vec4 tmp = cells[top];
|
|
cells[top] = cells[bot];
|
|
cells[bot] = tmp;
|
|
// update cached props
|
|
float tmpB = behaviors[top]; behaviors[top] = behaviors[bot]; behaviors[bot] = tmpB;
|
|
float tmpD = densities[top]; densities[top] = densities[bot]; densities[bot] = tmpD;
|
|
}
|
|
}
|
|
}
|
|
|
|
// 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 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 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 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 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;
|
|
}
|
|
}
|
|
|
|
fragColor = cells[localIndex];
|
|
}
|