From d4b030f46c3a643e813cf31e3faa2b4f3662a160 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 3 Oct 2021 13:57:19 +0300
Subject: [PATCH] Support multiple lights in a single pass

Light direction is now computed in fragment shader because interface
variable locations can't use specialization constants.

Shadow map currently only affects the first light but will be improved
soon.
---
 shaderlib/common.glsl         | 10 +++++++---
 shaderlib/cooktorrance.glsl   | 12 ++++++++----
 shaderlib/msp_interface.glsl  |  5 +++--
 shaderlib/phong.glsl          | 11 +++++++----
 shaderlib/shadow.glsl         |  2 +-
 source/materials/lighting.cpp | 11 +++++++++++
 6 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/shaderlib/common.glsl b/shaderlib/common.glsl
index dd8ac11f..b393b2a0 100644
--- a/shaderlib/common.glsl
+++ b/shaderlib/common.glsl
@@ -38,7 +38,7 @@ void standard_transform()
 	mat4 vertex_tf = get_vertex_transform();
 	mat3 normal_tf = get_normal_transform();
 
-	vec4 world_vertex = vertex_tf*get_vertex_position();
+	out vec4 world_vertex = vertex_tf*get_vertex_position();
 	vec4 eye_vertex = eye_world_matrix*world_vertex;
 	gl_Position = clip_eye_matrix*eye_vertex;
 
@@ -50,8 +50,6 @@ void standard_transform()
 	vec3 eye_pos = (inverse(eye_world_matrix)*vec4(0.0, 0.0, 0.0, 1.0)).xyz;
 	out vec3 world_look_dir = normalize(world_vertex.xyz-eye_pos);
 
-	out vec3 world_light_dir = light_sources[0].position.xyz-world_vertex.xyz*light_sources[0].position.w;
-
 	out float fog_coord = eye_vertex.z;
 
 	if(use_clipping)
@@ -83,6 +81,12 @@ virtual vec3 get_fragment_normal()
 		return normalize(world_normal);
 }
 
+virtual vec3 get_light_direction(int index)
+{
+	vec4 light_pos = light_sources[index].position;
+	return normalize(light_pos.xyz-world_vertex.xyz*light_pos.w);
+}
+
 virtual vec3 get_environment_sample(vec3 direction, float roughness)
 {
 	float lod = (2-roughness)*roughness*(textureQueryLevels(environment_map)-1);
diff --git a/shaderlib/cooktorrance.glsl b/shaderlib/cooktorrance.glsl
index 4b0c4dc8..7eefbf60 100644
--- a/shaderlib/cooktorrance.glsl
+++ b/shaderlib/cooktorrance.glsl
@@ -151,10 +151,14 @@ vec3 cooktorrance_environment(vec3 normal, vec3 look, vec3 base_color, float met
 
 vec3 cooktorrance_lighting(vec3 normal, vec3 look, vec3 base_color, float metalness, float roughness)
 {
-	vec3 light = normalize(world_light_dir);
-
-	float shadow = get_shadow_factor(0);
-	vec3 color = cooktorrance_one_light_direct(normal, look, light, light_sources[0].color, base_color, metalness, roughness)*shadow;
+	vec3 color = vec3(0.0);
+	for(int i=0; i<max_lights; ++i)
+		if(light_sources[i].enabled!=0)
+		{
+			vec3 light = get_light_direction(i);
+			float shadow = get_shadow_factor(i);
+			color += cooktorrance_one_light_direct(normal, look, light, light_sources[i].color, base_color, metalness, roughness)*shadow;
+		}
 
 	color += cooktorrance_environment(normal, look, base_color, metalness, roughness);
 
diff --git a/shaderlib/msp_interface.glsl b/shaderlib/msp_interface.glsl
index 6c229da0..23c61205 100644
--- a/shaderlib/msp_interface.glsl
+++ b/shaderlib/msp_interface.glsl
@@ -2,6 +2,7 @@ struct LightSourceParameters
 {
 	vec4 position;
 	vec3 color;
+	int enabled;
 };
 
 struct ClipPlane
@@ -19,10 +20,10 @@ uniform CameraTransform
 	mat4 eye_clip_matrix;
 };
 
+layout(constant_id=auto) const int max_lights = 4;
 uniform Lighting
 {
-	// Declared as an array for compatibility reasons
-	LightSourceParameters light_sources[1];
+	LightSourceParameters light_sources[max_lights];
 	vec4 ambient_color;
 	vec4 fog_color;
 	float fog_density;
diff --git a/shaderlib/phong.glsl b/shaderlib/phong.glsl
index 7d8dc295..87eba5ea 100644
--- a/shaderlib/phong.glsl
+++ b/shaderlib/phong.glsl
@@ -94,11 +94,14 @@ vec3 phong_one_light(vec3 light, vec3 normal, vec3 look, vec3 light_color, vec3
 
 vec3 phong_lighting(vec3 normal, vec3 look, vec3 surface_diffuse, vec3 surface_specular, float shininess)
 {
-	vec3 light = normalize(world_light_dir);
-
 	vec3 color = phong_ambient(surface_diffuse);
-	float shadow = get_shadow_factor(0);
-	color += phong_one_light(light, normal, look, light_sources[0].color, surface_diffuse, surface_specular, shininess)*shadow;
+	for(int i=0; i<max_lights; ++i)
+		if(light_sources[i].enabled!=0)
+		{
+			vec3 light = get_light_direction(i);
+			float shadow = get_shadow_factor(i);
+			color += phong_one_light(light, normal, look, light_sources[i].color, surface_diffuse, surface_specular, shininess)*shadow;
+		}
 
 	if(use_emission)
 		color += get_emission_color();
diff --git a/shaderlib/shadow.glsl b/shaderlib/shadow.glsl
index 04cf6832..65b003f4 100644
--- a/shaderlib/shadow.glsl
+++ b/shaderlib/shadow.glsl
@@ -21,7 +21,7 @@ virtual float get_shadow_factor(int index)
 {
 	if(use_shadow_map)
 	{
-		if(shadow_coord.x<0 || shadow_coord.x>1 || shadow_coord.y<0 || shadow_coord.y>1)
+		if(index>0 || shadow_coord.x<0 || shadow_coord.x>1 || shadow_coord.y<0 || shadow_coord.y>1)
 			return 1.0;
 		float shadow_sample = texture(shadow_map, shadow_coord);
 		return mix(1.0, shadow_sample, shadow_darkness);
diff --git a/source/materials/lighting.cpp b/source/materials/lighting.cpp
index 20c812fe..cd04d1b4 100644
--- a/source/materials/lighting.cpp
+++ b/source/materials/lighting.cpp
@@ -17,6 +17,14 @@ Lighting::Lighting()
 	set_ambient(0.2f);
 	set_fog_color(Color(0.0f, 0.0f, 0.0f, 0.0f));
 	set_fog_density(0.0f);
+
+	for(unsigned i=0; i<8; ++i)
+	{
+		string base = format("light_sources[%d]", i);
+		shdata.uniform(base+".position", Vector4(0, 0, 1, 0));
+		shdata.uniform(base+".color", 0.0f, 0.0f, 0.0f);
+		shdata.uniform(base+".enabled", 0);
+	}
 }
 
 void Lighting::set_ambient(const Color &a)
@@ -55,7 +63,10 @@ void Lighting::detach(const Light &l)
 {
 	auto i = find_member(lights, &l, &AttachedLight::light);
 	if(i!=lights.end())
+	{
 		lights.erase(i);
+		shdata.uniform(format("light_sources[%d].enabled", lights.size()), 0);
+	}
 }
 
 const ProgramData &Lighting::get_shader_data() const
-- 
2.43.0