OpenSpace/modules/gaia/shaders/gaia_point_ge.glsl

/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2021                                                               *
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#version __CONTEXT__

#include "floatoperations.glsl"

const float EPS = 1e-5;

layout(points) in;
in vec2 vs_brightness[];
in vec4 vs_gPosition[];
in float vs_starDistFromSun[];
in float vs_cameraDistFromSun[];

layout(points, max_vertices = 1) out;
out vec2 ge_brightness;
out vec4 ge_gPosition;
out float ge_starDistFromSun;
out float ge_cameraDistFromSun;
out float ge_observedDist;

uniform dmat4 view;
uniform float viewScaling;
uniform float cutOffThreshold;

void main() {
    ge_brightness = vs_brightness[0];
    ge_starDistFromSun = vs_starDistFromSun[0];
    ge_cameraDistFromSun = vs_cameraDistFromSun[0];

    vec4 viewPosition = vec4(view * vs_gPosition[0]);

    ge_observedDist = safeLength(viewPosition / viewScaling);
    float distThreshold = cutOffThreshold - log(ge_observedDist) / log(4.0);

    vec4 position = gl_in[0].gl_Position;

    // Discard geometry if star has no position (but wasn't a nullArray).
    // Or if observed distance is above threshold set by cutOffThreshold.
    // By discarding in gs instead of fs we save computations for when nothing is visible.
    if (length(position) < EPS || distThreshold <= 0) {
        return;
    }

    //gl_PointSize = 1.0;
    gl_Position = position;
    gl_Position.z = 0.0;
    ge_gPosition = viewPosition;

    EmitVertex();

    EndPrimitive();
}