Merge https://github.com/coelckers/gzdoom

src/gl/models/gl_models.cpp

@@ -787,6 +787,10 @@ void gl_InitModels()
 							map[c]=1;
 						}
 					}
+					else if (sc.Compare("dontcullbackfaces"))
+					{
+						smf.flags |= MDL_DONTCULLBACKFACES;
+					}
 					else
 					{
 						sc.ScriptMessage("Unrecognized string \"%s\"", sc.String);
@@ -949,8 +953,9 @@ void gl_RenderModel(GLSprite * spr)
 	gl_RenderState.EnableTexture(true);
 	// [BB] In case the model should be rendered translucent, do back face culling.
 	// This solves a few of the problems caused by the lack of depth sorting.
+	// [Nash] Don't do back face culling if explicitly specified in MODELDEF
 	// TO-DO: Implement proper depth sorting.
-	if (!( spr->actor->RenderStyle == LegacyRenderStyles[STYLE_Normal] ))
+	if (!(spr->actor->RenderStyle == LegacyRenderStyles[STYLE_Normal]) && !(smf->flags & MDL_DONTCULLBACKFACES))
 	{
 		glEnable(GL_CULL_FACE);
 		glFrontFace(GL_CW);
@@ -1012,6 +1017,9 @@ void gl_RenderModel(GLSprite * spr)
 	// Model space => World space
 	gl_RenderState.mModelMatrix.translate(spr->x, spr->z, spr->y );	
 
+	// [Nash] take SpriteRotation into account
+	angle += spr->actor->SpriteRotation.Degrees;
+
 	if (spr->actor->renderflags & RF_INTERPOLATEANGLES)
 	{
 		// [Nash] use interpolated angles

src/gl/models/gl_models.h

@@ -370,6 +370,7 @@ enum
 	MDL_USEACTORPITCH				= 32,
 	MDL_USEACTORROLL				= 64,
 	MDL_BADROTATION					= 128,
+	MDL_DONTCULLBACKFACES			= 256,
 };
 
 struct FSpriteModelFrame