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#version 150
// The render target's resolution (used for scaling)
uniform vec2 resolution;
// The billboards' size
uniform vec2 size;
// Input is the passed point cloud
layout (points) in;
// The output will consist of triangle strips with four vertices each
layout (triangle_strip, max_vertices = 4) out;
// Output texture coordinates
out vec2 tex_coord;
// Main entry point
void main()
{
// Caculate the half width/height of the billboards
vec2 half_size = size / 2.f;
// Scale the size based on resolution (1 would be full width/height)
half_size /= resolution;
// Iterate over all vertices
for (int i = 0; i < gl_in.length(); i++)
{
// Retrieve the passed vertex position
vec2 pos = gl_in[i].gl_Position.xy;
// Bottom left vertex
gl_Position = vec4(pos - half_size, 0.f, 1.f);
tex_coord = vec2(1.f, 1.f);
EmitVertex();
// Bottom right vertex
gl_Position = vec4(pos.x + half_size.x, pos.y - half_size.y, 0.f, 1.f);
tex_coord = vec2(0.f, 1.f);
EmitVertex();
// Top left vertex
gl_Position = vec4(pos.x - half_size.x, pos.y + half_size.y, 0.f, 1.f);
tex_coord = vec2(1.f, 0.f);
EmitVertex();
// Top right vertex
gl_Position = vec4(pos + half_size, 0.f, 1.f);
tex_coord = vec2(0.f, 0.f);
EmitVertex();
// And finalize the primitive
EndPrimitive();
}
}
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