OpenSpace/modules/base/shaders/renderabletrail_vs.glsl

/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2019                                                               *
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#version __CONTEXT__

#include "PowerScaling/powerScaling_vs.hglsl"

layout(location = 0) in vec3 in_point_position;

out vec4 vs_positionScreenSpace;
out vec4 vs_gPosition;
out float fade;
out float v_pointSize;

uniform dmat4 modelViewTransform;
uniform mat4 projectionTransform;
uniform int idOffset;
uniform int nVertices;
uniform bool useLineFade;
uniform float lineFade;
uniform int vertexSortingMethod;
uniform int pointSize;
uniform int stride;

// Fragile! Keep in sync with RenderableTrail::render
#define VERTEX_SORTING_NEWESTFIRST 0
#define VERTEX_SORTING_OLDESTFIRST 1
#define VERTEX_SORTING_NOSORTING 2


void main() {
    int modId = gl_VertexID;

    if ((vertexSortingMethod != VERTEX_SORTING_NOSORTING) && useLineFade) {
        // Account for a potential rolling buffer
        modId = gl_VertexID - idOffset;
        if (modId < 0) {
            modId += nVertices;
        }

        // Convert the index to a [0,1] ranger
        float id = float(modId) / float(nVertices);

        if (vertexSortingMethod == VERTEX_SORTING_NEWESTFIRST) {
            id = 1.0 - id;
        }

        fade = clamp(id * lineFade, 0.0, 1.0); 
    }
    else {
        fade = 1.0;
    }

    vs_gPosition = vec4(modelViewTransform * dvec4(in_point_position, 1));
    vs_positionScreenSpace = z_normalization(projectionTransform * vs_gPosition);

    gl_PointSize = (stride == 1 || int(modId) % stride == 0) ? float(pointSize) : float(pointSize) / 2;
    v_pointSize  = gl_PointSize;
    gl_Position  = vs_positionScreenSpace;
}