From f16a7df6135262c91fee2a2f6c46ad2f3caa7157 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Thu, 13 Apr 2023 02:15:41 +0100
Subject: Update shaders to use material to conditionally lookup sub-texture in
 the atlas

---
 gfx/gl/shaders/basicShader.fs         | 16 ++++++++++++++--
 gfx/gl/shaders/basicShader.vs         |  1 +
 gfx/gl/shaders/landmassShader.vs      |  1 +
 gfx/gl/shaders/materialInterface.glsl |  3 +++
 gfx/gl/shaders/meshIn.glsl            |  1 +
 5 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/gfx/gl/shaders/basicShader.fs b/gfx/gl/shaders/basicShader.fs
index 8bb6350..ab5e58b 100644
--- a/gfx/gl/shaders/basicShader.fs
+++ b/gfx/gl/shaders/basicShader.fs
@@ -1,14 +1,26 @@
 #version 330 core
+#extension GL_ARB_shading_language_420pack : enable
 
 include(`materialInterface.glsl')
 include(`geometryOut.glsl')
 
-uniform sampler2D texture0;
+layout(binding = 0) uniform sampler2D texture0;
+layout(binding = 1) uniform usampler2DRect material;
+
+vec4 getTextureColour(uint midx, vec2 uv)
+{
+	if (midx > 0u) {
+		const vec2 tSize = textureSize(texture0, 0);
+		const vec4 sPosSize = texture(material, uvec2(0, midx - 1u));
+		uv = (sPosSize.xy + sPosSize.zw * fract(uv)) / tSize;
+	}
+	return texture(texture0, uv);
+}
 
 void
 main()
 {
-	vec4 textureColour = texture(texture0, TexCoords);
+	vec4 textureColour = getTextureColour(Material, TexCoords);
 	float clear = round(mix(textureColour.a, 1, Colour.a));
 	gPosition = vec4(FragPos, clear);
 	gNormal = vec4(Normal, clear);
diff --git a/gfx/gl/shaders/basicShader.vs b/gfx/gl/shaders/basicShader.vs
index 4d648f3..e1701ed 100644
--- a/gfx/gl/shaders/basicShader.vs
+++ b/gfx/gl/shaders/basicShader.vs
@@ -15,6 +15,7 @@ main()
 	TexCoords = texCoord;
 	Normal = (model * vec4(normal, 0.0)).xyz;
 	Colour = colour;
+	Material = material;
 
 	gl_Position = viewProjection * worldPos;
 }
diff --git a/gfx/gl/shaders/landmassShader.vs b/gfx/gl/shaders/landmassShader.vs
index cabe39f..0cc8153 100644
--- a/gfx/gl/shaders/landmassShader.vs
+++ b/gfx/gl/shaders/landmassShader.vs
@@ -12,6 +12,7 @@ main()
 	TexCoords = texCoord;
 	Normal = normal;
 	Colour = colour;
+	Material = material;
 
 	gl_Position = viewProjection * vec4(position, 1.0);
 }
diff --git a/gfx/gl/shaders/materialInterface.glsl b/gfx/gl/shaders/materialInterface.glsl
index 3e09c85..5735cf9 100644
--- a/gfx/gl/shaders/materialInterface.glsl
+++ b/gfx/gl/shaders/materialInterface.glsl
@@ -2,3 +2,6 @@ ifelse(TYPE, .fs, in, out) vec3 FragPos;
 ifelse(TYPE, .fs, in, out) vec2 TexCoords;
 ifelse(TYPE, .fs, in, out) vec3 Normal;
 ifelse(TYPE, .fs, in, out) vec4 Colour;
+flat
+ifelse(TYPE, .fs, in, out)
+uint Material;
diff --git a/gfx/gl/shaders/meshIn.glsl b/gfx/gl/shaders/meshIn.glsl
index 2b244c1..dd84a10 100644
--- a/gfx/gl/shaders/meshIn.glsl
+++ b/gfx/gl/shaders/meshIn.glsl
@@ -2,3 +2,4 @@ layout(location = 0) in vec3 position;
 layout(location = 1) in vec2 texCoord;
 layout(location = 2) in vec3 normal;
 layout(location = 3) in vec4 colour;
+layout(location = 4) in uint material;
-- 
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