From a21cbb6fa7c62014eb5ffea6c8f096c2b0737c38 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sun, 27 Nov 2022 12:38:26 +0000
Subject: Change pointlight render area definition to a cube

---
 gfx/gl/shaders/pointLight.gs | 47 ++++++++++++++++++++++----------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

(limited to 'gfx/gl/shaders/pointLight.gs')

diff --git a/gfx/gl/shaders/pointLight.gs b/gfx/gl/shaders/pointLight.gs
index 2bd71e9..03d131d 100644
--- a/gfx/gl/shaders/pointLight.gs
+++ b/gfx/gl/shaders/pointLight.gs
@@ -2,43 +2,44 @@
 #extension GL_ARB_enhanced_layouts : enable
 #extension GL_ARB_shading_language_420pack : enable
 
-const int maxv = 128;
-const int maxarcs = (maxv / 2) - 1;
-const int minarcs = 10;
-const float tau = radians(360);
-const float scale = 150;
-uniform ivec4 viewPort;
+const vec3[] cube = vec3[]( // http://www.cs.umd.edu/gvil/papers/av_ts.pdf
+		vec3(-1, 1, 1), // Front-top-left
+		vec3(1, 1, 1), // Front-top-right
+		vec3(-1, -1, 1), // Front-bottom-left
+		vec3(1, -1, 1), // Front-bottom-right
+		vec3(1, -1, -1), // Back-bottom-right
+		vec3(1, 1, 1), // Front-top-right
+		vec3(1, 1, -1), // Back-top-right
+		vec3(-1, 1, 1), // Front-top-left
+		vec3(-1, 1, -1), // Back-top-left
+		vec3(-1, -1, 1), // Front-bottom-left
+		vec3(-1, -1, -1), // Back-bottom-left
+		vec3(1, -1, -1), // Back-bottom-right
+		vec3(-1, 1, -1), // Back-top-left
+		vec3(1, 1, -1) // Back-top-right
+);
+uniform mat4 viewProjection;
 
 in vec3 centre[];
 in float size[];
 layout(points) in;
 
-layout(triangle_strip, max_vertices = maxv) out;
-out vec3 geo_centre;
+layout(triangle_strip, max_vertices = cube.length()) out;
+out vec4 geo_centre;
 
 void
-doSeg(float arc, vec2 radius)
+doVertex(int idx)
 {
-	gl_Position = gl_in[0].gl_Position;
-	geo_centre = centre[0];
-	EmitVertex();
-
-	const vec2 off = vec2(cos(arc), sin(arc)) * radius;
-	gl_Position.xy = gl_in[0].gl_Position.xy + off;
-	geo_centre = centre[0];
+	gl_Position = viewProjection * (gl_in[0].gl_Position + vec4(cube[idx] * size[0], 1));
+	geo_centre = vec4(centre[0], size[0]);
 	EmitVertex();
 }
 
 void
 main()
 {
-	const vec2 display = viewPort.zw;
-	const vec2 ratio = vec2(1, display.x / display.y);
-	const vec2 radius = (size[0] * ratio * scale) / gl_in[0].gl_Position.w;
-	const float step = tau / clamp(radius.x, minarcs, maxarcs);
-	for (float arc = 0; arc < tau; arc += step) {
-		doSeg(arc, radius);
+	for (int i = 0; i < cube.length(); ++i) {
+		doVertex(i);
 	}
-	doSeg(tau, radius);
 	EndPrimitive();
 }
-- 
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