From fe02c8f4019d00c095a65cbad316f02dc199a428 Mon Sep 17 00:00:00 2001
From: kichikuou <KichikuouChrome@gmail.com>
Date: Sun, 10 Jul 2022 13:20:50 +0900
Subject: [PATCH] ReignEngine: Implement rim lighting

Lighting parameters are per-material and are stored in the .amt file.
---
 shaders/reign.f.glsl | 9 ++++++++-
 src/3d/3d_internal.h | 9 +++++++++
 src/3d/model.c       | 6 ++++++
 src/3d/renderer.c    | 5 +++++
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/shaders/reign.f.glsl b/shaders/reign.f.glsl
index bafb563..c6275a6 100644
--- a/shaders/reign.f.glsl
+++ b/shaders/reign.f.glsl
@@ -30,6 +30,8 @@ uniform dir_light dir_lights[NR_DIR_LIGHTS];
 uniform vec3 specular_light_dir;
 uniform float specular_strength;
 uniform float specular_shininess;
+uniform float rim_exponent;
+uniform vec3 rim_color;
 uniform vec3 view_pos;
 
 in vec2 tex_coord;
@@ -39,6 +41,7 @@ out vec4 frag_color;
 
 void main() {
 	vec3 norm = normalize(normal);
+	vec3 view_dir = normalize(view_pos - frag_pos);
 	vec3 frag_rgb = ambient;
 
 	// Diffuse lighting
@@ -52,11 +55,15 @@ void main() {
 
 	// Specular lighting
 	if (specular_strength > 0.0) {
-		vec3 view_dir = normalize(view_pos - frag_pos);
 		vec3 reflect_dir = reflect(specular_light_dir, norm);
 		float specular = pow(max(dot(view_dir, reflect_dir), 0.0), specular_shininess) * specular_strength;
 		frag_rgb += vec3(specular);
 	}
 
+	// Rim lighting
+	if (rim_exponent > 0) {
+		frag_rgb += pow(1.0 - max(dot(norm, view_dir), 0.0), rim_exponent) * rim_color;
+	}
+
 	frag_color = vec4(frag_rgb, texel.a * alpha_mod);
 }
diff --git a/src/3d/3d_internal.h b/src/3d/3d_internal.h
index 5292d31..db1b22a 100644
--- a/src/3d/3d_internal.h
+++ b/src/3d/3d_internal.h
@@ -50,6 +50,8 @@ struct material {
 	bool opaque;
 	float specular_strength;
 	float specular_shininess;
+	float rim_exponent;
+	vec3 rim_color;
 };
 
 struct bone {
@@ -90,6 +92,8 @@ struct RE_renderer {
 	GLint specular_light_dir;
 	GLint specular_strength;
 	GLint specular_shininess;
+	GLint rim_exponent;
+	GLint rim_color;
 	GLint view_pos;
 
 	// Attribute variable locations
@@ -220,6 +224,11 @@ struct amt_material {
 enum amt_field_index {
 	AMT_SPECULAR_STRENGTH = 0,
 	AMT_SPECULAR_SHININESS = 2,
+	// amt v5+
+	AMT_RIM_EXPONENT = 7,
+	AMT_RIM_R = 8,
+	AMT_RIM_G = 9,
+	AMT_RIM_B = 10,
 };
 
 struct pol *pol_parse(uint8_t *data, size_t size);
diff --git a/src/3d/model.c b/src/3d/model.c
index f8df832..c03ed4d 100644
--- a/src/3d/model.c
+++ b/src/3d/model.c
@@ -80,6 +80,12 @@ static bool init_material(struct material *material, const struct pol_material *
 	if (amt_m) {
 		material->specular_strength = amt_m->fields[AMT_SPECULAR_STRENGTH];
 		material->specular_shininess = amt_m->fields[AMT_SPECULAR_SHININESS];
+		if (amt->version >= 5) {
+			material->rim_exponent = amt_m->fields[AMT_RIM_EXPONENT];
+			material->rim_color[0] = amt_m->fields[AMT_RIM_R];
+			material->rim_color[1] = amt_m->fields[AMT_RIM_G];
+			material->rim_color[2] = amt_m->fields[AMT_RIM_B];
+		}
 	}
 
 	return true;
diff --git a/src/3d/renderer.c b/src/3d/renderer.c
index e8e3d21..d577edd 100644
--- a/src/3d/renderer.c
+++ b/src/3d/renderer.c
@@ -82,6 +82,8 @@ struct RE_renderer *RE_renderer_new(struct texture *texture)
 	r->specular_light_dir = glGetUniformLocation(r->shader.program, "specular_light_dir");
 	r->specular_strength = glGetUniformLocation(r->shader.program, "specular_strength");
 	r->specular_shininess = glGetUniformLocation(r->shader.program, "specular_shininess");
+	r->rim_exponent = glGetUniformLocation(r->shader.program, "rim_exponent");
+	r->rim_color = glGetUniformLocation(r->shader.program, "rim_color");
 	r->view_pos = glGetUniformLocation(r->shader.program, "view_pos");
 	r->vertex_normal = glGetAttribLocation(r->shader.program, "vertex_normal");
 	r->vertex_uv = glGetAttribLocation(r->shader.program, "vertex_uv");
@@ -273,6 +275,8 @@ static void render_model(struct RE_instance *inst, struct RE_renderer *r)
 			glUniform1f(r->specular_strength, 0.0);
 			glUniform1f(r->specular_shininess, 0.0);
 		}
+		glUniform1f(r->rim_exponent, material->rim_exponent);
+		glUniform3fv(r->rim_color, 1, material->rim_color);
 
 		glActiveTexture(GL_TEXTURE0);
 		glBindTexture(GL_TEXTURE_2D, material->color_map);
@@ -336,6 +340,7 @@ static void render_billboard(struct RE_instance *inst, struct RE_renderer *r, ma
 	glUniform1f(r->alpha_mod, inst->alpha);
 	glUniform1f(r->specular_strength, 0.0);
 	glUniform1f(r->specular_shininess, 0.0);
+	glUniform1f(r->rim_exponent, 0.0);
 
 	glActiveTexture(GL_TEXTURE0);
 	glBindTexture(GL_TEXTURE_2D, bt->texture);