Fix calculation of apparent size (#6872)

Author: BMagnu

code/model/modelrender.cpp

@@ -2049,17 +2049,17 @@ void model_render_glow_points(const polymodel *pm, const polymodel_instance *pmi
 
 // These scaling functions were adapted from Elecman's code.
 // https://forum.unity.com/threads/this-script-gives-you-objects-screen-size-in-pixels.48966/#post-2107126
-float convert_pixel_size_and_distance_to_diameter(float pixelsize, float distance, float field_of_view_deg, int screen_height)
+float convert_pixel_size_and_distance_to_diameter(float pixelsize, float distance, float field_of_view, int screen_width)
 {
-	float diameter = (pixelsize * distance * field_of_view_deg) / (fl_degrees(screen_height));
+	float diameter = (pixelsize * distance * tanf(field_of_view)) / (screen_width);
 	return diameter;
 }
 
 // These scaling functions were adapted from Elecman's code.
 // https://forum.unity.com/threads/this-script-gives-you-objects-screen-size-in-pixels.48966/#post-2107126
-float convert_distance_and_diameter_to_pixel_size(float distance, float diameter, float field_of_view_deg, int screen_height)
+float convert_distance_and_diameter_to_pixel_size(float distance, float diameter, float field_of_view, int screen_width)
 {
-	float pixel_size = (diameter * fl_degrees(screen_height)) / (distance * field_of_view_deg);
+	float pixel_size = (diameter * screen_width) / (distance * tanf(field_of_view));
 	return pixel_size;
 }
 
@@ -2073,16 +2073,16 @@ float model_render_get_diameter_clamped_to_min_pixel_size(const vec3d* pos, floa
 	float current_pixel_size = convert_distance_and_diameter_to_pixel_size(
 		distance_to_eye,
 		diameter,
-		fl_degrees(g3_get_hfov(Eye_fov)),
-		gr_screen.max_h);
+		g3_get_hfov(Eye_fov),
+		gr_screen.max_w);
 
 	float scaled_diameter = diameter;
 	if (current_pixel_size < min_pixel_size) {
 		scaled_diameter = convert_pixel_size_and_distance_to_diameter(
 			min_pixel_size,
 			distance_to_eye,
-			fl_degrees(g3_get_hfov(Eye_fov)),
-			gr_screen.max_h);
+			g3_get_hfov(Eye_fov),
+			gr_screen.max_w);
 	}
 
 	return scaled_diameter;

code/model/modelrender.h

@@ -311,7 +311,7 @@ void model_render_arc(const vec3d* v1, const vec3d* v2, const SCP_vector<vec3d>
 void model_render_set_wireframe_color(const color* clr);
 bool render_tech_model(tech_render_type model_type, int x1, int y1, int x2, int y2, float zoom, bool lighting, int class_idx, const matrix* orient, const SCP_string& pof_filename = "", float closeup_zoom = 0, const vec3d* closeup_pos = &vmd_zero_vector, const SCP_string& tcolor = "");
 
-float convert_distance_and_diameter_to_pixel_size(float distance, float diameter, float field_of_view_deg, int screen_height);
+float convert_distance_and_diameter_to_pixel_size(float distance, float diameter, float field_of_view, int screen_width);
 
 float model_render_get_diameter_clamped_to_min_pixel_size(const vec3d* pos, float diameter, float min_pixel_size);
 

code/particle/ParticleEffect.cpp

@@ -130,8 +130,8 @@ float ParticleEffect::getApproximateVisualSize(const vec3d& pos) const {
 	return convert_distance_and_diameter_to_pixel_size(
 		distance_to_eye,
 		m_radius.avg() * 2.f,
-		fl_degrees(g3_get_hfov(Eye_fov)),
-		gr_screen.max_h);
+		g3_get_hfov(Eye_fov),
+		gr_screen.max_w);
 }
 
 float ParticleEffect::getCurrentFrequencyMult(decltype(modular_curves_definition)::input_type_t source) const {

code/utils/RandomRange.h

@@ -144,6 +144,9 @@ class RandomRange {
 	 */
 	ValueType avg() const
 	{
+		if (m_constant)
+			return m_minValue;
+
 		if constexpr (has_member(DistributionType, avg())) {
 			return m_distribution.avg();
 		}

code/weapon/weapons.cpp

@@ -10200,7 +10200,7 @@ float weapon_get_apparent_size(const weapon& wp) {
 
 	return convert_distance_and_diameter_to_pixel_size(
 		dist,
-		wep_objp->radius,
-		fl_degrees(g3_get_hfov(Eye_fov)),
-		gr_screen.max_h) / i2fl(gr_screen.max_h);
+		wep_objp->radius * 2.0f,
+		g3_get_hfov(Eye_fov),
+		gr_screen.max_w) / i2fl(gr_screen.max_w);
 }