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[vertex]
layout(location=0) in highp vec4 vertex_attrib;
layout(location=4) in vec2 uv_in;
uniform float offset_x;
out vec2 uv_interp;
void main() {
uv_interp = uv_in;
gl_Position = vec4(vertex_attrib.x + offset_x, vertex_attrib.y, 0.0, 1.0);
}
[fragment]
uniform sampler2D source; //texunit:0
uniform vec2 eye_center;
uniform float k1;
uniform float k2;
uniform float upscale;
uniform float aspect_ratio;
in vec2 uv_interp;
layout(location = 0) out vec4 frag_color;
void main() {
vec2 coords = uv_interp;
vec2 offset = coords - eye_center;
// take aspect ratio into account
offset.y /= aspect_ratio;
// distort
vec2 offset_sq = offset * offset;
float radius_sq = offset_sq.x + offset_sq.y;
float radius_s4 = radius_sq * radius_sq;
float distortion_scale = 1.0 + (k1 * radius_sq) + (k2 * radius_s4);
offset *= distortion_scale;
// reapply aspect ratio
offset.y *= aspect_ratio;
// add our eye center back in
coords = offset + eye_center;
coords /= upscale;
// and check our color
if (coords.x < -1.0 || coords.y < -1.0 || coords.x > 1.0 || coords.y > 1.0) {
frag_color = vec4(0.0, 0.0, 0.0, 1.0);
} else {
coords = (coords + vec2(1.0)) / vec2(2.0);
frag_color = textureLod(source, coords, 0.0);
}
}
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