Add area light material

include/material.h

@@ -22,6 +22,14 @@
 		.params = { .dielectric = { .eta = e } }, \
 	}
 
+#define AREA_LIGHT(r, g, b, l) \
+	{ \
+		.scatter = scatter_area_light, \
+		.params = { \
+			.area_light = { .colour = { r, g, b }, .luminosity = l }, \
+		}, \
+	}
+
 typedef struct {
 	vec3_t point, normal;
 	double t;
@@ -41,10 +49,16 @@ typedef struct {
 	double eta;
 } dielectric_params_t;
 
+typedef struct {
+	vec3_t colour;
+	double luminosity;
+} area_light_params_t;
+
 typedef union {
 	lambertian_params_t lambertian;
 	reflective_params_t reflective;
 	dielectric_params_t dielectric;
+	area_light_params_t area_light;
 } material_params_t;
 
 typedef bool scatter_fn_t(
@@ -65,5 +79,8 @@ bool scatter_reflective(
 bool scatter_dielectric(
     material_params_t params, hit_t hit, rng_t *rng, ray_t *ray,
     vec3_t *atten_out);
+bool scatter_area_light(
+    material_params_t params, hit_t hit, rng_t *rng, ray_t *ray,
+    vec3_t *atten_out);
 
 #endif

src/material.c

@@ -68,3 +68,16 @@ bool scatter_dielectric(
 
 	return true;
 }
+
+bool scatter_area_light(
+    material_params_t params, hit_t hit, rng_t *rng, ray_t *ray,
+    vec3_t *atten_out)
+{
+	(void)hit;
+	(void)rng;
+	(void)ray;
+
+	*atten_out
+	    = vec3_scale(params.area_light.colour, params.area_light.luminosity);
+	return false;
+}