////////////////////////////////////////////////////////////////////////////////////////
//
//  Copyright 2026 OVITO GmbH, Germany
//
//  This file is part of OVITO (Open Visualization Tool).
//
//  OVITO is free software; you can redistribute it and/or modify it either under the
//  terms of the GNU General Public License version 3 as published by the Free Software
//  Foundation (the "GPL") or, at your option, under the terms of the MIT License.
//  If you do not alter this notice, a recipient may use your version of this
//  file under either the GPL or the MIT License.
//
//  You should have received a copy of the GPL along with this program in a
//  file LICENSE.GPL.txt.  You should have received a copy of the MIT License along
//  with this program in a file LICENSE.MIT.txt
//
//  This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND,
//  either express or implied. See the GPL or the MIT License for the specific language
//  governing rights and limitations.
//
////////////////////////////////////////////////////////////////////////////////////////

layout(points) in;
layout(triangle_strip, max_vertices=4) out;

#include "../../global_uniforms.glsl"

// Inputs:
in vec3 position_gs[1];
in float radius_gs[1];
in vec4 color_gs[1];
uniform vec2 unit_quad_triangle_strip[4];

// Outputs:
flat out vec4 color_fs;
void main()
{
    for(int corner = 0; corner < 4; corner++)
    {
        // Transform particle center to view space.
        vec3 eye_position = (modelview_matrix * vec4(position_gs[0], 1.0)).xyz;

        // Apply additional scaling due to model-view transformation to particle radius.
        float viewspace_radius = radius_gs[0] * length(modelview_matrix[0]);

        // Project corner vertex.
        gl_Position = projection_matrix * (vec4(eye_position, 1.0) + vec4(unit_quad_triangle_strip[corner] * viewspace_radius, 0.0, 0.0));

        // Forward particle color to fragment shader.
        color_fs = color_gs[0];

        EmitVertex();
    }
    EndPrimitive();
}
