From 0d1deddae57a4dcdb9eaa1e31e8405888a1357d6 Mon Sep 17 00:00:00 2001
From: Magnus Norddahl <dpjudas@users.noreply.github.com>
Date: Thu, 2 Mar 2017 19:10:57 +0100
Subject: [PATCH] Bind shadow map texture for main.fp and sample from the
 shadowmap texture

---
 src/gl/dynlights/gl_shadowmap.cpp  |  2 ++
 src/gl/shaders/gl_shader.cpp       |  3 +++
 wadsrc/static/shaders/glsl/main.fp | 34 ++++++++++++++++++++++++++++--
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/gl/dynlights/gl_shadowmap.cpp b/src/gl/dynlights/gl_shadowmap.cpp
index b1c95ff03a..b70304db0a 100644
--- a/src/gl/dynlights/gl_shadowmap.cpp
+++ b/src/gl/dynlights/gl_shadowmap.cpp
@@ -67,6 +67,8 @@ void FShadowMap::Update()
 	glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 2, 0);
 	glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 3, 0);
 
+	GLRenderer->mBuffers->BindShadowMapTexture(16);
+
 	FGLDebug::PopGroup();
 }
 
diff --git a/src/gl/shaders/gl_shader.cpp b/src/gl/shaders/gl_shader.cpp
index 421139050c..d36f4c4fa7 100644
--- a/src/gl/shaders/gl_shader.cpp
+++ b/src/gl/shaders/gl_shader.cpp
@@ -270,6 +270,9 @@ bool FShader::Load(const char * name, const char * vert_prog_lump, const char *
 		if (tempindex > 0) glUniform1i(tempindex, i - 1);
 	}
 
+	int shadowmapindex = glGetUniformLocation(hShader, "ShadowMap");
+	if (shadowmapindex > 0) glUniform1i(shadowmapindex, 16);
+
 	glUseProgram(0);
 	return !!linked;
 }
diff --git a/wadsrc/static/shaders/glsl/main.fp b/wadsrc/static/shaders/glsl/main.fp
index 2e27e57702..0d4cf0607e 100644
--- a/wadsrc/static/shaders/glsl/main.fp
+++ b/wadsrc/static/shaders/glsl/main.fp
@@ -26,6 +26,7 @@ out vec4 FragNormal;
 
 
 uniform sampler2D tex;
+uniform sampler2D ShadowMap;
 
 vec4 Process(vec4 color);
 vec4 ProcessTexel();
@@ -132,6 +133,34 @@ float R_DoomLightingEquation(float light)
 	return lightscale;
 }
 
+//===========================================================================
+//
+// Check if light is in shadow according to its 1D shadow map
+//
+//===========================================================================
+
+float shadowmapAttenuation(vec4 lightpos, float shadowIndex)
+{
+	float u;
+	float v = (abs(shadowIndex) + 0.5) / 1024.0;
+	vec2 dir = (pixelpos.xz - lightpos.xz);
+	if (abs(dir.x) > abs(dir.y))
+	{
+		if (dir.x >= 0.0)
+			u = dir.y / dir.x * 0.125 + (0.25 + 0.125);
+		else
+			u = dir.y / dir.x * 0.125 + (0.75 + 0.125);
+	}
+	else
+	{
+		if (dir.y >= 0.0)
+			u = dir.x / dir.y * 0.125 + 0.125;
+		else
+			u = dir.x / dir.y * 0.125 + (0.50 + 0.125);
+	}
+	return texture(ShadowMap, vec2(u, v)).x < dot(dir, dir) ? 1.0 : 0.0;
+}
+
 //===========================================================================
 //
 // Standard lambertian diffuse light calculation
@@ -151,10 +180,11 @@ float diffuseContribution(vec3 lightDirection, vec3 normal)
 //
 //===========================================================================
 
-float pointLightAttenuation(vec4 lightpos, float attenuate)
+float pointLightAttenuation(vec4 lightpos, float shadowIndex)
 {
 	float attenuation = max(lightpos.w - distance(pixelpos.xyz, lightpos.xyz),0.0) / lightpos.w;
-	if (attenuate >= 0.0) // Sign bit is the attenuate flag
+	attenuation *= shadowmapAttenuation(lightpos, shadowIndex);
+	if (shadowIndex >= 0.0) // Sign bit is the attenuated light flag
 	{
 		return attenuation;
 	}