From 50d6f63fb28c82a35e68914fe941b685d26f6e89 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Wed, 23 Nov 2022 19:07:18 +0000
Subject: Add rendering support for point lights

---
 gfx/gl/shaders/pointLight.fs | 27 +++++++++++++++++++++++++++
 gfx/gl/shaders/pointLight.gs | 44 ++++++++++++++++++++++++++++++++++++++++++++
 gfx/gl/shaders/pointLight.vs | 18 ++++++++++++++++++
 3 files changed, 89 insertions(+)
 create mode 100644 gfx/gl/shaders/pointLight.fs
 create mode 100644 gfx/gl/shaders/pointLight.gs
 create mode 100644 gfx/gl/shaders/pointLight.vs

(limited to 'gfx/gl/shaders')

diff --git a/gfx/gl/shaders/pointLight.fs b/gfx/gl/shaders/pointLight.fs
new file mode 100644
index 0000000..18407fe
--- /dev/null
+++ b/gfx/gl/shaders/pointLight.fs
@@ -0,0 +1,27 @@
+#version 330 core
+#extension GL_ARB_shading_language_420pack : enable
+
+out vec3 FragColor;
+
+layout(binding = 0) uniform sampler2D gPosition;
+layout(binding = 1) uniform sampler2D gNormal;
+uniform ivec4 viewPort;
+uniform vec3 colour;
+uniform float kq;
+in vec3 geo_centre;
+
+void
+main()
+{
+	const vec2 texCoord = gl_FragCoord.xy / viewPort.zw;
+	const vec3 position = texture(gPosition, texCoord).xyz;
+	const vec3 normal = texture(gNormal, texCoord).xyz;
+	const vec3 lightv = position - geo_centre;
+	const float lightDist = length(lightv);
+	const vec3 lightDirection = normalize(lightv);
+	const float normalDot = dot(-lightDirection, normal);
+	if (normalDot < 0) {
+		discard;
+	}
+	FragColor = (colour * normalDot) / (1 + (kq * pow(lightDist, 2)));
+}
diff --git a/gfx/gl/shaders/pointLight.gs b/gfx/gl/shaders/pointLight.gs
new file mode 100644
index 0000000..2bd71e9
--- /dev/null
+++ b/gfx/gl/shaders/pointLight.gs
@@ -0,0 +1,44 @@
+#version 330 core
+#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;
+
+in vec3 centre[];
+in float size[];
+layout(points) in;
+
+layout(triangle_strip, max_vertices = maxv) out;
+out vec3 geo_centre;
+
+void
+doSeg(float arc, vec2 radius)
+{
+	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];
+	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);
+	}
+	doSeg(tau, radius);
+	EndPrimitive();
+}
diff --git a/gfx/gl/shaders/pointLight.vs b/gfx/gl/shaders/pointLight.vs
new file mode 100644
index 0000000..6236c33
--- /dev/null
+++ b/gfx/gl/shaders/pointLight.vs
@@ -0,0 +1,18 @@
+#version 330 core
+
+layout(location = 0) in vec3 position;
+
+uniform vec3 colour;
+uniform float kq;
+uniform mat4 viewProjection;
+
+out vec3 centre;
+out float size;
+
+void
+main()
+{
+	centre = position;
+	size = sqrt(256 * max(max(colour.r, colour.g), colour.b) / kq);
+	gl_Position = viewProjection * vec4(centre, 1);
+}
-- 
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