- track level start time for the shader system, reset the shaders.

src/g_levellocals.h

@@ -67,6 +67,8 @@ struct FLevelLocals
 	FString		F1Pic;
 	EMapType	maptype;
 
+	uint64_t	ShaderStartTime = 0;	// tell the shader system when we started the level (forces a timer restart)
+
 	TArray<vertex_t> vertexes;
 	TArray<sector_t> sectors;
 	TArray<line_t*> linebuffer;	// contains the line lists for the sectors.

src/gl/renderer/gl_renderstate.cpp

@@ -37,6 +37,7 @@
 #include "gl/renderer/gl_colormap.h"
 #include "gl/dynlights//gl_lightbuffer.h"
 #include "gl/renderer/gl_renderbuffers.h"
+#include "g_levellocals.h"
 
 void gl_SetTextureMode(int type);
 
@@ -121,7 +122,7 @@ bool FRenderState::ApplyShader()
 	static uint64_t firstFrame = 0;
 	// if firstFrame is not yet initialized, initialize it to current time
 	// if we're going to overflow a float (after ~4.6 hours, or 24 bits), re-init to regain precision
-	if ((firstFrame == 0) || (screen->FrameTime - firstFrame >= 1<<24))
+	if ((firstFrame == 0) || (screen->FrameTime - firstFrame >= 1<<24) || level.ShaderStartTime > firstFrame)
 		firstFrame = screen->FrameTime;
 
 	static const float nulvec[] = { 0.f, 0.f, 0.f, 0.f };

src/p_setup.cpp

@@ -3627,6 +3627,8 @@ void P_SetupLevel (const char *lumpname, int position)
 	bool buildmap;
 	const int *oldvertextable = NULL;
 
+	level.ShaderStartTime = I_msTime(); // indicate to the shader system that the level just started
+
 	// This is motivated as follows:
 
 	bool RequireGLNodes = Renderer->RequireGLNodes() || am_textured;