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//PARTICLE DEPTH VERTEX SHADER
#version 400

in vec3 vertexPos;

uniform mat4 projection;
uniform mat4 mView;
uniform vec2 screenSize;
uniform vec3 lightPos;

out vec3 pos;
out float radius;

void main() {
        vec4 viewPos = mView * vec4(vertexPos, 1.0);
    float dist = length(viewPos);
    gl_Position = projection * viewPos;
    //gl_PointSize = 6 * screenSize.y / (8.0 * gl_Position.z);
    gl_PointSize = 1.0 * (200.0 / dist);

    pos = viewPos.xyz;
    radius = gl_PointSize;
}


//PARTICLE DEPTH FRAGMENT SHADER
#version 400

in vec3 pos;
in float radius;

uniform mat4 mView;
uniform mat4 projection;
uniform vec2 screenSize;
uniform vec3 lightPos;

out float depth;

float linearizeDepth(float depth) {
        float n = 0.01f;
        float f = 100f;

        return (2.0 * n) / (f + n - depth * (f - n));
}

void main() {
        //calculate normal
        vec3 normal;
        normal.xy = gl_PointCoord * 2.0 - 1.0;
        float r2 = dot(normal.xy, normal.xy);

        if (r2 > 1.0) {
                discard;
        }

        normal.z = sqrt(1.0 - r2);

        //calculate depth
        vec4 pixelPos = vec4(pos + normal * radius, 1.0);
        vec4 clipSpacePos = projection * pixelPos;

        depth = clipSpacePos.z / clipSpacePos.w * 0.5f + 0.5f;
        depth = linearizeDepth(depth);
}


//OUTPUT VERTEX SHADER
#version 400

in vec2 vertexPos;

out vec2 pos;

void main() {
        pos = 0.5f * vertexPos + 0.5f;
        gl_Position = vec4(vertexPos, 0.0f, 1.0f);
}

//OUTPUT FRAGMENT SHADER
#version 400

in vec2 coord;

uniform sampler2D depthMap;
uniform vec2 screenSize;
uniform mat4 projection;

out vec4 color;

float linearizeDepth(float depth) {
        float n = 0.01f;
        float f = 100f;

        return (2.0 * n) / (f + n - depth * (f - n));
}

void main() {
        float curDepth = texture2D(depthMap, coord).x;
        //curDepth = linearizeDepth(curDepth);
        color = vec4(curDepth);
}