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export const vertex = /* glsl */ `
precision mediump float;
attribute vec2 position;
attribute vec4 color;
attribute vec3 center;
attribute vec3 covA;
attribute vec3 covB;
uniform mat4 projection, view;
uniform vec2 focal;
uniform vec2 viewport;
varying vec4 vColor;
varying vec2 vPosition;
mat3 transpose(mat3 m) {
return mat3(
m[0][0], m[1][0], m[2][0],
m[0][1], m[1][1], m[2][1],
m[0][2], m[1][2], m[2][2]
);
}
void main () {
vec4 camspace = view * vec4(center, 1);
vec4 pos2d = projection * camspace;
float bounds = 1.2 * pos2d.w;
if (pos2d.z < -pos2d.w || pos2d.x < -bounds || pos2d.x > bounds
|| pos2d.y < -bounds || pos2d.y > bounds) {
gl_Position = vec4(0.0, 0.0, 2.0, 1.0);
return;
}
mat3 Vrk = mat3(
covA.x, covA.y, covA.z,
covA.y, covB.x, covB.y,
covA.z, covB.y, covB.z
);
mat3 J = mat3(
focal.x / camspace.z, 0., -(focal.x * camspace.x) / (camspace.z * camspace.z),
0., -focal.y / camspace.z, (focal.y * camspace.y) / (camspace.z * camspace.z),
0., 0., 0.
);
mat3 W = transpose(mat3(view));
mat3 T = W * J;
mat3 cov = transpose(T) * Vrk * T;
vec2 vCenter = vec2(pos2d) / pos2d.w;
float diagonal1 = cov[0][0] + 0.3;
float offDiagonal = cov[0][1];
float diagonal2 = cov[1][1] + 0.3;
float mid = 0.5 * (diagonal1 + diagonal2);
float radius = length(vec2((diagonal1 - diagonal2) / 2.0, offDiagonal));
float lambda1 = mid + radius;
float lambda2 = max(mid - radius, 0.1);
vec2 diagonalVector = normalize(vec2(offDiagonal, lambda1 - diagonal1));
vec2 v1 = min(sqrt(2.0 * lambda1), 1024.0) * diagonalVector;
vec2 v2 = min(sqrt(2.0 * lambda2), 1024.0) * vec2(diagonalVector.y, -diagonalVector.x);
vColor = color;
vPosition = position;
gl_Position = vec4(
vCenter
+ position.x * v1 / viewport * 2.0
+ position.y * v2 / viewport * 2.0, 0.0, 1.0
);
}
`;
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