Add BillboardProgram to SceneShader

The implementation is overly simple/incomplete, I'm not even convince
what is there is right, but it's a decent start.

1 files changed, 23 insertions, 0 deletions

diff --git a/gfx/gl/shaders/billboard.vert b/gfx/gl/shaders/billboard.vert
new file mode 100644
index 0000000..2d73084
--- /dev/null
+++ b/gfx/gl/shaders/billboard.vert
@@ -0,0 +1,23 @@
+#version 460 core
+
+uniform mat4 viewProjection;
+uniform ivec4 viewPort;
+uniform ivec3 viewPoint;
+uniform vec3 centre;
+uniform float size;
+layout(location = 0) in ivec3 modelPos;
+layout(location = 1) in float yaw;
+
+flat out ivec3 ModelPos;
+flat out float Yaw;
+flat out float Depth;
+
+void
+main()
+{
+	ModelPos = modelPos;
+	Yaw = yaw;
+	gl_Position = viewProjection * vec4(modelPos - viewPoint + centre, 1);
+	Depth = gl_Position.w;
+	gl_PointSize = (viewPort.w * size * 2) / gl_Position.w;
+}