From db8a3651cdeab0c3e45232e2cc65954e6568ef6f Mon Sep 17 00:00:00 2001
From: Goober5000 <ipw47@mailbox.org>
Date: Mon, 25 Mar 2024 13:27:16 -0400
Subject: [PATCH] additional lighting fixes

Fix a minor oversight from #6014; in the ship lab, there are sometimes no suns at all, so remove the assertion.  The lighting check is only needed for supernovas anyway, so make that clear.

Additionally, add further clarification for the distinction between suns, lights, and variables used only for the supernova.  Finally fix one more sun/light discrepancy that escaped notice from #6014.

Fixes an assertion in the ship lab.  Follow-up to #6014.
---
 code/lighting/lighting.cpp |  2 +-
 freespace2/freespace.cpp   | 29 +++++++++++++++--------------
 2 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/code/lighting/lighting.cpp b/code/lighting/lighting.cpp
index 387e2c5c412..63f96a183e6 100644
--- a/code/lighting/lighting.cpp
+++ b/code/lighting/lighting.cpp
@@ -314,7 +314,7 @@ void light_rotate_all()
  */
 int light_get_global_count()
 {
-	return (int)Static_light.size();
+	return static_cast<int>(Static_light.size());
 }
 
 /**
diff --git a/freespace2/freespace.cpp b/freespace2/freespace.cpp
index 39424ea25f4..f507d0d2312 100644
--- a/freespace2/freespace.cpp
+++ b/freespace2/freespace.cpp
@@ -665,16 +665,14 @@ float Supernova_last_glare = 0.0f;
 void game_sunspot_process(float frametime)
 {
 	TRACE_SCOPE(tracing::SunspotProcess);
-	int n_lights, idx;
 	float Sun_spot_goal = 0.0f;
 
-	int sun_idx = 0;
-	int light_idx = light_find_for_sun(sun_idx);
-	Assertion(light_idx >= 0, "Could not find sun for light index %d!", sun_idx);
+	int supernova_sun_idx = 0;
+	int supernova_light_idx = light_find_for_sun(supernova_sun_idx);
 
 	// supernova
 	auto sn_stage = supernova_stage();
-	if (sn_stage != SUPERNOVA_STAGE::NONE) {
+	if (sn_stage != SUPERNOVA_STAGE::NONE && supernova_light_idx >= 0) {
 		// sunspot differently based on supernova stage
 		switch (sn_stage) {
 		// this case is only here to make gcc happy - apparently it doesn't know we already checked for it
@@ -689,7 +687,7 @@ void game_sunspot_process(float frametime)
 			pct = supernova_sunspot_pct();
 
 			vec3d light_dir;				
-			light_get_global_dir(&light_dir, light_idx);
+			light_get_global_dir(&light_dir, supernova_light_idx);
 			float dot;
 			dot = vm_vec_dot( &light_dir, &Eye_matrix.vec.fvec );
 			
@@ -702,9 +700,9 @@ void game_sunspot_process(float frametime)
 			}
 
 			// draw the sun glow
-			if ( !shipfx_eye_in_shadow( &Eye_position, Viewer_obj, light_idx ) )	{
+			if ( !shipfx_eye_in_shadow( &Eye_position, Viewer_obj, supernova_light_idx ) )	{
 				// draw the glow for this sun
-				stars_draw_sun_glow(sun_idx);
+				stars_draw_sun_glow(supernova_sun_idx);
 			}
 
 			Supernova_last_glare = Sun_spot_goal;
@@ -741,24 +739,27 @@ void game_sunspot_process(float frametime)
 		Sun_spot_goal = 0.0f;
 		if ( Sun_drew )	{
 			// check sunspots for all suns
-			n_lights = light_get_global_count();
+			int n_lights = light_get_global_count();
 
 			// check
-			for(idx=0; idx<n_lights; idx++)	{
-				bool in_shadow = shipfx_eye_in_shadow(&Eye_position, Viewer_obj, idx);
+			for(int light_idx=0; light_idx<n_lights; light_idx++)	{
+				bool in_shadow = shipfx_eye_in_shadow(&Eye_position, Viewer_obj, light_idx);
 
 				if (!in_shadow) {
 					vec3d light_dir;				
-					light_get_global_dir(&light_dir, idx);
+					light_get_global_dir(&light_dir, light_idx);
 
 					//only do sunglare stuff if this light source has one
-					if (light_has_glare(idx))	{
+					if (light_has_glare(light_idx))	{
 						float dot = vm_vec_dot( &light_dir, &Eye_matrix.vec.fvec )*0.5f+0.5f;
 						Sun_spot_goal += (float)pow(dot,85.0f);
 					}
 
 					// draw the glow for this sun
-					stars_draw_sun_glow(idx);				
+					int sun_idx = light_get_sun_index(light_idx);
+					if (sun_idx >= 0) {
+						stars_draw_sun_glow(sun_idx);
+					}
 				}
 			}